DNA
Fact & Fiction
Fact & Fiction
Joma Sipe -
OS SONS DA SERENIDADE l THE SOUNDS OF STILLNESS (Illuminated Version)
MUTATION
Only recent discoveries in genetics have shown the role stress places on the individual that affect the immune system and turns genes on and off. B-cell receptors hypermutate at extraordinary rates until they unlock the key to the pathogen and engage it, activating other parts of the immune system to respond.
When [micro]organisms are under threat, they meet it in a way that mobilizes them so they hypermute until suddenly an adaptation emerges that neutralizes the threat. The mutations are not slow and random. The same goes on in us.
OS SONS DA SERENIDADE l THE SOUNDS OF STILLNESS (Illuminated Version)
MUTATION
Only recent discoveries in genetics have shown the role stress places on the individual that affect the immune system and turns genes on and off. B-cell receptors hypermutate at extraordinary rates until they unlock the key to the pathogen and engage it, activating other parts of the immune system to respond.
When [micro]organisms are under threat, they meet it in a way that mobilizes them so they hypermute until suddenly an adaptation emerges that neutralizes the threat. The mutations are not slow and random. The same goes on in us.
https://www.newscientist.com/article/dn23240-the-father-of-all-men-is-340000-years-old/#.V3Wnv3arD5s.facebook
The father of all men is 340,000 years old
Often genetic ancestry relies on the Y chromosome, which is inherited only via the paternal line, or mitochondrial DNA, which is only passed on from mothers. These make for persuasive – but often simplistic – analyses of ancestry. These two chunks of DNA make up 2% of your genome. But the other 98% has to come from somewhere too, and that is a pick-and-mix from all the rest of your ancestors.
Each subsequent generation, the contribution from an individual from your lineage becomes less. Professor Mark Thomas from University College London describes this dilution as “homeopathic”. After a few rounds of preparation, homeopathic dilutions contain no molecules of whatever the active ingredient is imagined to be. Genetic inheritance works in a similar way. Half of your genome comes from your mother and half from your father, a quarter from each of your grandparents. But because of the way the DNA deck is shuffled every time a sperm or egg is made, it doesn’t keep halving perfectly as you meander up through your family tree. If you’re fully outbred (which you aren’t), you should have 256 great-great-great-great-great-great-grandparents. But their genetic contribution to you is not equal. Before long, you will find ancestors from whom you bear no DNA. They are your family, your blood, but their genes have been diluted out of your bloodline. Even though you are directly descended from Charlemagne, you may well carry none of his DNA.
But we are all special, which means none of us are. If you’re vaguely of European extraction, you are also the fruits of Charlemagne’s prodigious loins. A fecund ruler, he sired at least 18 children by motley wives and concubines, including Charles the Younger, Pippin the Hunchback, Drogo of Metz, Hruodrud, Ruodhaid, and not forgetting Hugh.
This is merely a numbers game. You have two parents, four grandparents, eight great-grandparents, and so on. But this ancestral expansion is not borne back ceaselessly into the past. If it were, your family tree when Charlemagne was Le Grand Fromage would harbour more than a billion ancestors – more people than were alive then. What this means is that pedigrees begin to fold in on themselves a few generations back, and become less arboreal, and more web-like. In 2013, geneticists Peter Ralph and Graham Coop showed that all Europeans are descended from exactly the same people. Basically, everyone alive in the ninth century who left descendants is the ancestor of every living European today, including Charlemagne, Drogo, Pippin and Hugh. Quel dommage.
With the advent of cheap genetic sequencing, the deep, intimate history of everyone can be revealed. We carry the traces of our ancestors in our cells, and now, for the price of a secondhand copy of Burke’s Peerage, you can have your illustrious past unscrambled. Plenty of companies have emerged that provide this service, such as 23andMe and Ancestry DNA. Spit in a test tube, and they will match parts of your DNA with people from all over the world. The results are beguiling, but don’t necessarily show your geographical origins in the past. They show with whom you have common ancestry today.
People love discovering that they’re a bit Viking, or a bit Saracen. This is big business nowadays, and some companies spin fabulous yarns about your forebears as marketing devices. I’ve been making a documentary for Radio 4 on what genetics can and can’t tell you about ancestry, and examining some of the more outlandish claims that some ancestry businesses make. One company offered a service whereby it would tell you the precise village location of your genetic ancestry 1,000 years ago. It’s a peculiar thing to claim, as you will have thousands of ancestors 1,000 years ago, and I’m pretty sure they won’t have all come from the same village. Their algorithm clearly needed some work: it placed the genetic origin of one paying customer in the depths of the Humber estuary.
The truth is that we all are a bit of everything, and we come from all over. If you’re white, you’re a bit Viking. And a bit Celt. And a bit Anglo-Saxon. And a bit Charlemagne. This is not to disparage genetic genealogy and ancestry. Done right, it is an immensely powerful tool for studying families and human migrations. DNA can disclose unknown cousins or parents. Further back, the past becomes dimmer, but not invisible. A dazzling, detailed analysis of the British genome last month scrutinised the history of immigration over the past 10,000 years. Expect many more studies like this from all over the world revealing all manner of dalliances from the foggy past.
Often genetic ancestry relies on the Y chromosome, which is inherited only via the paternal line, or mitochondrial DNA, which is only passed on from mothers. These make for persuasive – but often simplistic – analyses of ancestry. These two chunks of DNA make up 2% of your genome. But the other 98% has to come from somewhere too, and that is a pick-and-mix from all the rest of your ancestors.
Each subsequent generation, the contribution from an individual from your lineage becomes less. Professor Mark Thomas from University College London describes this dilution as “homeopathic”. After a few rounds of preparation, homeopathic dilutions contain no molecules of whatever the active ingredient is imagined to be. Genetic inheritance works in a similar way. Half of your genome comes from your mother and half from your father, a quarter from each of your grandparents. But because of the way the DNA deck is shuffled every time a sperm or egg is made, it doesn’t keep halving perfectly as you meander up through your family tree. If you’re fully outbred (which you aren’t), you should have 256 great-great-great-great-great-great-grandparents. But their genetic contribution to you is not equal. Before long, you will find ancestors from whom you bear no DNA. They are your family, your blood, but their genes have been diluted out of your bloodline. Even though you are directly descended from Charlemagne, you may well carry none of his DNA.
So what does this all mean? Ancestry is messy. Genetics is messy, but powerful. People are horny. Life is complex. Anyone who says differently is selling something. A secret history is hidden in the mosaics of our genomes, but caveat emptor. If you want to spend your cash on someone in a white coat telling you that you’re descended from Vikings or Saxons or Charlemagne or even Drogo of Metz, help yourself. I, or hundreds of geneticists around the world, will shrug and do it for free, and you don’t even need to spit in a tube.
The Business of Genetic Ancestry is on BBC Radio 4, Tuesday 26 May at 11am
https://www.theguardian.com/science/commentisfree/2015/may/24/business-genetic-ancestry-charlemagne-adam-rutherford
Each subsequent generation, the contribution from an individual from your lineage becomes less. Professor Mark Thomas from University College London describes this dilution as “homeopathic”. After a few rounds of preparation, homeopathic dilutions contain no molecules of whatever the active ingredient is imagined to be. Genetic inheritance works in a similar way. Half of your genome comes from your mother and half from your father, a quarter from each of your grandparents. But because of the way the DNA deck is shuffled every time a sperm or egg is made, it doesn’t keep halving perfectly as you meander up through your family tree. If you’re fully outbred (which you aren’t), you should have 256 great-great-great-great-great-great-grandparents. But their genetic contribution to you is not equal. Before long, you will find ancestors from whom you bear no DNA. They are your family, your blood, but their genes have been diluted out of your bloodline. Even though you are directly descended from Charlemagne, you may well carry none of his DNA.
But we are all special, which means none of us are. If you’re vaguely of European extraction, you are also the fruits of Charlemagne’s prodigious loins. A fecund ruler, he sired at least 18 children by motley wives and concubines, including Charles the Younger, Pippin the Hunchback, Drogo of Metz, Hruodrud, Ruodhaid, and not forgetting Hugh.
This is merely a numbers game. You have two parents, four grandparents, eight great-grandparents, and so on. But this ancestral expansion is not borne back ceaselessly into the past. If it were, your family tree when Charlemagne was Le Grand Fromage would harbour more than a billion ancestors – more people than were alive then. What this means is that pedigrees begin to fold in on themselves a few generations back, and become less arboreal, and more web-like. In 2013, geneticists Peter Ralph and Graham Coop showed that all Europeans are descended from exactly the same people. Basically, everyone alive in the ninth century who left descendants is the ancestor of every living European today, including Charlemagne, Drogo, Pippin and Hugh. Quel dommage.
With the advent of cheap genetic sequencing, the deep, intimate history of everyone can be revealed. We carry the traces of our ancestors in our cells, and now, for the price of a secondhand copy of Burke’s Peerage, you can have your illustrious past unscrambled. Plenty of companies have emerged that provide this service, such as 23andMe and Ancestry DNA. Spit in a test tube, and they will match parts of your DNA with people from all over the world. The results are beguiling, but don’t necessarily show your geographical origins in the past. They show with whom you have common ancestry today.
People love discovering that they’re a bit Viking, or a bit Saracen. This is big business nowadays, and some companies spin fabulous yarns about your forebears as marketing devices. I’ve been making a documentary for Radio 4 on what genetics can and can’t tell you about ancestry, and examining some of the more outlandish claims that some ancestry businesses make. One company offered a service whereby it would tell you the precise village location of your genetic ancestry 1,000 years ago. It’s a peculiar thing to claim, as you will have thousands of ancestors 1,000 years ago, and I’m pretty sure they won’t have all come from the same village. Their algorithm clearly needed some work: it placed the genetic origin of one paying customer in the depths of the Humber estuary.
The truth is that we all are a bit of everything, and we come from all over. If you’re white, you’re a bit Viking. And a bit Celt. And a bit Anglo-Saxon. And a bit Charlemagne. This is not to disparage genetic genealogy and ancestry. Done right, it is an immensely powerful tool for studying families and human migrations. DNA can disclose unknown cousins or parents. Further back, the past becomes dimmer, but not invisible. A dazzling, detailed analysis of the British genome last month scrutinised the history of immigration over the past 10,000 years. Expect many more studies like this from all over the world revealing all manner of dalliances from the foggy past.
Often genetic ancestry relies on the Y chromosome, which is inherited only via the paternal line, or mitochondrial DNA, which is only passed on from mothers. These make for persuasive – but often simplistic – analyses of ancestry. These two chunks of DNA make up 2% of your genome. But the other 98% has to come from somewhere too, and that is a pick-and-mix from all the rest of your ancestors.
Each subsequent generation, the contribution from an individual from your lineage becomes less. Professor Mark Thomas from University College London describes this dilution as “homeopathic”. After a few rounds of preparation, homeopathic dilutions contain no molecules of whatever the active ingredient is imagined to be. Genetic inheritance works in a similar way. Half of your genome comes from your mother and half from your father, a quarter from each of your grandparents. But because of the way the DNA deck is shuffled every time a sperm or egg is made, it doesn’t keep halving perfectly as you meander up through your family tree. If you’re fully outbred (which you aren’t), you should have 256 great-great-great-great-great-great-grandparents. But their genetic contribution to you is not equal. Before long, you will find ancestors from whom you bear no DNA. They are your family, your blood, but their genes have been diluted out of your bloodline. Even though you are directly descended from Charlemagne, you may well carry none of his DNA.
So what does this all mean? Ancestry is messy. Genetics is messy, but powerful. People are horny. Life is complex. Anyone who says differently is selling something. A secret history is hidden in the mosaics of our genomes, but caveat emptor. If you want to spend your cash on someone in a white coat telling you that you’re descended from Vikings or Saxons or Charlemagne or even Drogo of Metz, help yourself. I, or hundreds of geneticists around the world, will shrug and do it for free, and you don’t even need to spit in a tube.
The Business of Genetic Ancestry is on BBC Radio 4, Tuesday 26 May at 11am
https://www.theguardian.com/science/commentisfree/2015/may/24/business-genetic-ancestry-charlemagne-adam-rutherford
EVERYONE ON EARTH
IS ACTUALLY YOUR COUSIN
http://qz.com/557639/everyone-on-earth-is-actually-your-cousin/?utm_source=qzfb
IS ACTUALLY YOUR COUSIN
http://qz.com/557639/everyone-on-earth-is-actually-your-cousin/?utm_source=qzfb
http://roots4u.blogspot.com/2015/01/centimorgans-or-percentages.html
When I discuss relationships and DNA matching, I often do so in terms of percentages. It is one way that 23andMe lists their genetic matches, and the mathematics makes more sense to me and my analytical brain. I have posted a graphic with my blogs indicating how known relationships should theoretically match each other by percentages. Siblings match each other by 50%. Half-siblings match each other by 25%. First cousins match each other by 12.5%. And the biggest revelation for my search came when my mother matched Ken Ryder by over 4%; and I knew second cousins match on the average of 3.125%.
But not all DNA sites list percentages. And the total amount of DNA tested by each company varies slightly, as well as how they report it. Additionally, the percentages by which different sexes match is skewed a bit by counting the matches on the X-chromosome, as women have two of these to the man's one. Roughly, the centimorgans of DNA you match with another person divided by 6800-7100 should give you a ballpark percentage.
What the hell is a centimorgan anyway?
Wikipedia defines it this way. "In genetics, a centimorgan (abbreviated cM) ... is a unit for measuring genetic linkage. It is defined as the distance between chromosome positions (also termed, loci or markers) for which the expected average number of intervening chromosomal crossovers in a single generation is 0.01. It is often used to infer distance along a chromosome. It is not a true physical distance however."
So I am presenting you here with a chart similar to the one I have posted before in which the percentages of DNA are shown that you have in common with known stated relationships. This chart I give you today shows you the theoretical average of shared DNA you have with known stated relationships in centimorgans. This handy chart was made by Kristina Gow Dunnaway, and she gives permission for its reproduction and personal use. If you publish a book with this chart included and make a ton of money, that's another story, but I will leave copyright law to Judy Russell at Home - The Legal Genealogist.
You will see that the chart uses 6800 cM of autosomal DNA (atDNA) as its base figure for total DNA measured per person. This is the amount tested by FamilyTreeDNA. A more detailed discussion regarding the numbers game, the testing companies, and counting the pesky X-chromosome can be found at the International Society of Genetic Genealogy (ISOGG)'s wiki page at Autosomal DNA statistics - ISOGG Wiki. I have visited this page so often my browser recognizes it as soon as I type "au" only.
And remember, Mother Nature does not follow the rules set out on either one of the charts that I have given you. These are averages. The numbers are based on a purely theoretical assumption that DNA is passed perpetually in a tidy 50:50 split every generation. It is not. The only true 50:50 split you will ever get is a child compared to his or her parents.
The key to remember is that the larger the number, the more reliable the relationship assessment should be. I knew at the beginning of my search that my mother's father was not the man she thought he was, because she matched her sister by only 26% (1935 cM). There is no way you can make an argument for that being a full-sibling relationship. But as the numbers become smaller and smaller, the known relationship gets fuzzier and fuzzier.
Additionally, remember that if you have cousin marriages in your ancestry or come from a highly admixed population that may have had limited choices for marital partners, due to say religion or perhaps geographical isolation, the numbers become wonkier and less defining. The more families intermarry and their common ancestors' DNA is "reinserted" into their offspring, the more of it will be passed to the present generation. The numbers will be larger than expected.
When I discuss relationships and DNA matching, I often do so in terms of percentages. It is one way that 23andMe lists their genetic matches, and the mathematics makes more sense to me and my analytical brain. I have posted a graphic with my blogs indicating how known relationships should theoretically match each other by percentages. Siblings match each other by 50%. Half-siblings match each other by 25%. First cousins match each other by 12.5%. And the biggest revelation for my search came when my mother matched Ken Ryder by over 4%; and I knew second cousins match on the average of 3.125%.
But not all DNA sites list percentages. And the total amount of DNA tested by each company varies slightly, as well as how they report it. Additionally, the percentages by which different sexes match is skewed a bit by counting the matches on the X-chromosome, as women have two of these to the man's one. Roughly, the centimorgans of DNA you match with another person divided by 6800-7100 should give you a ballpark percentage.
What the hell is a centimorgan anyway?
Wikipedia defines it this way. "In genetics, a centimorgan (abbreviated cM) ... is a unit for measuring genetic linkage. It is defined as the distance between chromosome positions (also termed, loci or markers) for which the expected average number of intervening chromosomal crossovers in a single generation is 0.01. It is often used to infer distance along a chromosome. It is not a true physical distance however."
So I am presenting you here with a chart similar to the one I have posted before in which the percentages of DNA are shown that you have in common with known stated relationships. This chart I give you today shows you the theoretical average of shared DNA you have with known stated relationships in centimorgans. This handy chart was made by Kristina Gow Dunnaway, and she gives permission for its reproduction and personal use. If you publish a book with this chart included and make a ton of money, that's another story, but I will leave copyright law to Judy Russell at Home - The Legal Genealogist.
You will see that the chart uses 6800 cM of autosomal DNA (atDNA) as its base figure for total DNA measured per person. This is the amount tested by FamilyTreeDNA. A more detailed discussion regarding the numbers game, the testing companies, and counting the pesky X-chromosome can be found at the International Society of Genetic Genealogy (ISOGG)'s wiki page at Autosomal DNA statistics - ISOGG Wiki. I have visited this page so often my browser recognizes it as soon as I type "au" only.
And remember, Mother Nature does not follow the rules set out on either one of the charts that I have given you. These are averages. The numbers are based on a purely theoretical assumption that DNA is passed perpetually in a tidy 50:50 split every generation. It is not. The only true 50:50 split you will ever get is a child compared to his or her parents.
The key to remember is that the larger the number, the more reliable the relationship assessment should be. I knew at the beginning of my search that my mother's father was not the man she thought he was, because she matched her sister by only 26% (1935 cM). There is no way you can make an argument for that being a full-sibling relationship. But as the numbers become smaller and smaller, the known relationship gets fuzzier and fuzzier.
Additionally, remember that if you have cousin marriages in your ancestry or come from a highly admixed population that may have had limited choices for marital partners, due to say religion or perhaps geographical isolation, the numbers become wonkier and less defining. The more families intermarry and their common ancestors' DNA is "reinserted" into their offspring, the more of it will be passed to the present generation. The numbers will be larger than expected.
Long before mankind knew anything of DNA, the agnatic (pure male) and uterine (pure female) ancestries were given special significance...a person's cognates are all of his or her relatives in the agnatic and uterine lines.
Uterine: Pertaining to the reckoning of relationship by female link(s) exclusively, regardless of sex of Ego and/or Alter. Contra. "agnate".
- 1 : of the same or similar nature : generically alike
- 2 : related by blood; also : related on the mother's side
- 3 a : related by descent from the same ancestral language b of a word or morpheme : related by derivation, borrowing, or descent c of a substantive : related to a verb usually by derivation and serving as its object to reinforce the meaning
Uterine: Pertaining to the reckoning of relationship by female link(s) exclusively, regardless of sex of Ego and/or Alter. Contra. "agnate".
Long before we even knew about organic evolution (or about genetics, for that matter), we were already envisioning our genealogical ties to our ancestors as well as relatives in terms of blood, thereby making them seem more natural. As a result, we also tend to regard the essentially genealogical communities that are based on them (families, ethnic groups) as natural, organically delineated communities.
The very primitive animal layers are supposed to be inherited through the sympathetic system, and the relatively later animal layers belonging to the vertebrate series are represented by the cerebrospinal system. ~Carl Jung, 1925 Seminar, Page 140
Coalescence
The four main processes thought to affect population genetics -- mutation, genetic drift, gene flow, and selection -- are all unguided. The first three are random in their effect on evolution, meaning that they can be positive, negative or neutral in their effects on fitness; only natural selection acts in a directional manner to increase fitness.
The theory is that in small populations (smaller than a trillion, say) drift can overwhelm the power of selection. In such a case, organisms do not have sufficient numbers for beneficial mutations to arise and be fixed with any frequency. Most mutations are lost to drift before becoming established, even when they are beneficial. The significance of natural selection is thus greatly reduced in shaping evolutionary history.
The idea that evolution is driven by drift has led to a way of retrospectively estimating past genetic lineages. Called coalescent theory, it is based on one very simple assumption -- that the vast majority of mutations are neutral and have no effect on an organism's survival. (For a review go here.) Under this theory, actual genetic history is presumed not to matter. Our genomes are full of randomly accumulating neutral changes. When generating a genealogy for those changes, their order of appearance doesn't matter. Trees can be drawn and mutations assigned to them without regard to an evolutionary sequence of genotypes, since genotypes don't matter.
Here's the way a recent article put it:
... the genealogical relationship (gene tree) of neutral alleles can be simply depicted by a coalescence process in which lineages randomly coalesce with each other backward in time. The coalescence model is simple in the sense that it assumes little or no effect of evolutionary forces such as selection, recombination, and gene flow, instead giving a prominent role to random genetic drift.
Thus, according to this theory, if it can be assumed that most mutations or allelic states have no effect on fitness, a genealogy can be created randomly without any input from the genotype. Therefore the spread of variation can be modeled as a diffusion process or Markov chain run backwards, the mean time to coalescence can be estimated, and the effective population size can be estimated from that, based on mutation rate and generation time.
http://www.evolutionnews.org/2012/08/on_retrospectiv062881.html
The genetic patterns indicate that there was selection in the genome against the introgressed variants, so Neanderthals and modern humans exhibited hybrid breakdown. In light of no such genomic evidence for admixture of Eurasian ancestry into KhoeSan (I’ve asked, people have looked), that suggests we know that for hominins hybrid incompabilities seem to arise on the scale of between 200,000 and 600,000 years. It also seems that due meta-population dynamics lineage extinctions were very common in hominins. The genetic relatedness of Neanderthals across human swaths of territory indicate that they were subject to this dynamic, where there were massive lineage pruning events over the 600,000 years that this group was a distinct population. With modern humans, we now know that first settlers do not always leave a genetic impact later on because of extinction events. With these facts under our belt it is less surprising if there were “false dawns” of the “triumph of humanity.” What these results do warrant though is the final expiration of a particular narrative of the explosion of humanity ~50,000 years ago due to singular biological changes that cascaded themselves into a cultural explosion, where the hominin-made-man swept all before them. Probably the best illustration of this thesis can be found in Richard Klein’s 2002 book, The Dawn of Human Culture. In it he proposes that 50,000 years ago there was a single mutation which resulted in a pleiotropic cascade, and allowed for the emergence of full elaborated language and ergo the package of features which we associate with behavioral modernity. This model was presaged in the earlier decade with popularizations of “mitochondrial Eve” which implied that all humans were descended from a very small tribe resident in East Africa on the order of ~100,000 years ago. (the date varied as a function of the vicissitudes of mutational rate estimates)
Here’s what we know now that changes this. First, there are populations within Africa, in particular the the San of the far south, who diverged much earlier than 50,000 years ago. The most recent genomic estimates are suggesting divergence dates as early as ~200,000 years before the present. Second, the effective population size of humans outside of Africa is incredibly small, suggesting expansion from a very small founding population, but one should be cautious about generalizing to groups within Africa. That is, the blitzkrieg sweep model of modern human expansion does not hold to within Africa, and there is both archaeological and genomic inference to indicate the persistence of highly diverged hominin lineages in that continent until relatively recently. And, these lineages may have admixed with modern humans just as they have outside of Africa.
Finally, the emergence of H. sapiens sapiens supremacy seems to have been a process, not a singular event which emerged de novo like a supernovae in the hominin firmament. The Omo remains in Ethiopia were anatomically modern humans. The people who gave rise to Omo lived ~200,000 years ago. The encephalization of the human lineage increased gradually up until around ~200,000 years ago, and Neanderthals were famously the most encephalized of all. Therefore, some form of modern humans were present within Africa for 150,000 years while other lineages were dominant elsewhere. Remains from places like China suggest though that offshoots of African humanity did push into the rest of the world…but they may not have left much of a genetic trace. This may have been part of movements due to climate change during the Pleistocene, or one of the natural migrations which a consequence of Malthusian pressures and inter-deme competition which afflicted humans. But they clearly did not conquer all before them. Why? We don’t know. And we don’t know why the situation was different 50,000 years ago. As a null hypothesis one might entertain the possibility that it was random. That periodically turnovers occur, and it just so happened that an African lineage lucked out in a massive extinction event. But that’s hard to credit when you consider that these modern humans crossed into Sahul and Siberia after sweeping aside other groups, and then eventually crossed over into the New World. There was something different about us. Additionally, the modern humans eventually absorbed or extirpated other lineages within Africa too.
A generation ago many people thought they had the answer. That man was born 50,000 years ago on the East African plain, and the gods gave him the world. Only he was endowed with a soul. Today we know that that’s wrong. We just don’t know what’s right.
http://www.unz.com/gnxp/the-blood-of-the-first-men-runs-thin-in-our-kind/
The very primitive animal layers are supposed to be inherited through the sympathetic system, and the relatively later animal layers belonging to the vertebrate series are represented by the cerebrospinal system. ~Carl Jung, 1925 Seminar, Page 140
Coalescence
The four main processes thought to affect population genetics -- mutation, genetic drift, gene flow, and selection -- are all unguided. The first three are random in their effect on evolution, meaning that they can be positive, negative or neutral in their effects on fitness; only natural selection acts in a directional manner to increase fitness.
The theory is that in small populations (smaller than a trillion, say) drift can overwhelm the power of selection. In such a case, organisms do not have sufficient numbers for beneficial mutations to arise and be fixed with any frequency. Most mutations are lost to drift before becoming established, even when they are beneficial. The significance of natural selection is thus greatly reduced in shaping evolutionary history.
The idea that evolution is driven by drift has led to a way of retrospectively estimating past genetic lineages. Called coalescent theory, it is based on one very simple assumption -- that the vast majority of mutations are neutral and have no effect on an organism's survival. (For a review go here.) Under this theory, actual genetic history is presumed not to matter. Our genomes are full of randomly accumulating neutral changes. When generating a genealogy for those changes, their order of appearance doesn't matter. Trees can be drawn and mutations assigned to them without regard to an evolutionary sequence of genotypes, since genotypes don't matter.
Here's the way a recent article put it:
... the genealogical relationship (gene tree) of neutral alleles can be simply depicted by a coalescence process in which lineages randomly coalesce with each other backward in time. The coalescence model is simple in the sense that it assumes little or no effect of evolutionary forces such as selection, recombination, and gene flow, instead giving a prominent role to random genetic drift.
Thus, according to this theory, if it can be assumed that most mutations or allelic states have no effect on fitness, a genealogy can be created randomly without any input from the genotype. Therefore the spread of variation can be modeled as a diffusion process or Markov chain run backwards, the mean time to coalescence can be estimated, and the effective population size can be estimated from that, based on mutation rate and generation time.
http://www.evolutionnews.org/2012/08/on_retrospectiv062881.html
The genetic patterns indicate that there was selection in the genome against the introgressed variants, so Neanderthals and modern humans exhibited hybrid breakdown. In light of no such genomic evidence for admixture of Eurasian ancestry into KhoeSan (I’ve asked, people have looked), that suggests we know that for hominins hybrid incompabilities seem to arise on the scale of between 200,000 and 600,000 years. It also seems that due meta-population dynamics lineage extinctions were very common in hominins. The genetic relatedness of Neanderthals across human swaths of territory indicate that they were subject to this dynamic, where there were massive lineage pruning events over the 600,000 years that this group was a distinct population. With modern humans, we now know that first settlers do not always leave a genetic impact later on because of extinction events. With these facts under our belt it is less surprising if there were “false dawns” of the “triumph of humanity.” What these results do warrant though is the final expiration of a particular narrative of the explosion of humanity ~50,000 years ago due to singular biological changes that cascaded themselves into a cultural explosion, where the hominin-made-man swept all before them. Probably the best illustration of this thesis can be found in Richard Klein’s 2002 book, The Dawn of Human Culture. In it he proposes that 50,000 years ago there was a single mutation which resulted in a pleiotropic cascade, and allowed for the emergence of full elaborated language and ergo the package of features which we associate with behavioral modernity. This model was presaged in the earlier decade with popularizations of “mitochondrial Eve” which implied that all humans were descended from a very small tribe resident in East Africa on the order of ~100,000 years ago. (the date varied as a function of the vicissitudes of mutational rate estimates)
Here’s what we know now that changes this. First, there are populations within Africa, in particular the the San of the far south, who diverged much earlier than 50,000 years ago. The most recent genomic estimates are suggesting divergence dates as early as ~200,000 years before the present. Second, the effective population size of humans outside of Africa is incredibly small, suggesting expansion from a very small founding population, but one should be cautious about generalizing to groups within Africa. That is, the blitzkrieg sweep model of modern human expansion does not hold to within Africa, and there is both archaeological and genomic inference to indicate the persistence of highly diverged hominin lineages in that continent until relatively recently. And, these lineages may have admixed with modern humans just as they have outside of Africa.
Finally, the emergence of H. sapiens sapiens supremacy seems to have been a process, not a singular event which emerged de novo like a supernovae in the hominin firmament. The Omo remains in Ethiopia were anatomically modern humans. The people who gave rise to Omo lived ~200,000 years ago. The encephalization of the human lineage increased gradually up until around ~200,000 years ago, and Neanderthals were famously the most encephalized of all. Therefore, some form of modern humans were present within Africa for 150,000 years while other lineages were dominant elsewhere. Remains from places like China suggest though that offshoots of African humanity did push into the rest of the world…but they may not have left much of a genetic trace. This may have been part of movements due to climate change during the Pleistocene, or one of the natural migrations which a consequence of Malthusian pressures and inter-deme competition which afflicted humans. But they clearly did not conquer all before them. Why? We don’t know. And we don’t know why the situation was different 50,000 years ago. As a null hypothesis one might entertain the possibility that it was random. That periodically turnovers occur, and it just so happened that an African lineage lucked out in a massive extinction event. But that’s hard to credit when you consider that these modern humans crossed into Sahul and Siberia after sweeping aside other groups, and then eventually crossed over into the New World. There was something different about us. Additionally, the modern humans eventually absorbed or extirpated other lineages within Africa too.
A generation ago many people thought they had the answer. That man was born 50,000 years ago on the East African plain, and the gods gave him the world. Only he was endowed with a soul. Today we know that that’s wrong. We just don’t know what’s right.
http://www.unz.com/gnxp/the-blood-of-the-first-men-runs-thin-in-our-kind/
A piece of fossilized jaw discovered at Ledi-Geraru, Ethiopia, pushes back the date when the first members of the human genus evolved by 400,000 years. The research, in Science, shows that the jaw is about 2.8 million years old. It’s one of the few hominin fossils that date to between 2.5 million and 3 million years ago, when a small-brained australopith was evolving into the larger-brained Homo genus.
http://discovermagazine.com/2016/janfeb/28-the-first-of-our-kind
http://discovermagazine.com/2016/janfeb/28-the-first-of-our-kind
Suppose that you wanted a written record of your every ancestor…with the Ancestral Pyramid, a doubling of ancestors each generation back, by the 12th generation back you have 2048, and 60,000 direct ancestors going back to the Crusades. By Generation 40, you have more than one trillion ancestors.
Ancient DNA
http://www.dailymail.co.uk/sciencetech/article-3432060/An-unknown-chapter-human-history-took-place-Europe-15-000-years-ago-DNA-shows-hunter-gatherers-replaced-mystery-group-people-Ice-Age.html
http://www.scientificamerican.com/article/a-surprise-source-of-life-s-code/
Genetic Genealogy
You don't have DNA from all or even most of your ancestors. About 360 years is just short of 15 generations. At 15 generations, an individual living today would carry only three thousands of 1% (00.003052%) of the DNA of an ancestor who was “pure” anything 15 generations ago. So even if one ancestor was indeed Mediterranean 15 generations ago, unless they continuously intermarried within a pure Mediterranean population, the amount would drop by 50% with each
generation to the miniscule amount that would be found in today’s current generation. With today’s technology, this is simply untraceable in autosomal DNA. An autosomal DNA test only goes back 8 generations. For genealogy within the most recent fifteen generations, STR markers help define paternal lineages.
We have about 43 genetic ancestors out of 1024 genealogical ancestors after 10 generations. The probability of having DNA from all of your genealogical ancestors at a particular generation becomes vanishingly small very rapidly; there is a 99.6% chance that you will have DNA from all of your 16 great-great grandparents, only a 54% of sharing DNA with all 32 of your G-G-G grandparents, and a 0.01% chance for your 64 G-G-G-G grandparents. You only have to go back 5 generations for genealogical relatives to start dropping off your DNA tree.
We also care about how many genetic ancestors we have after a certain number of generations: The number of genetic ancestors starts off growing exponentially, but eventually flattens out to around 125 (at 10 generations, 120 of your 1024 genealogical ancestors are genetic ancestors).
The percentage of DNA you would carry from a single ancestor who lived 20,000 years ago, assuming you only descended from that ancestor 1 time, is infinitesimally small. There are more zeroes following that decimal point than I have patience to type. Let’s call that ancestor Xenia and let’s say she is a female.However, you did inherit DNA from many of your ancestors who lived 20,000 years ago, thousands of them, because all of them, through their descendants, make up the DNA you carry today.
So infinitesimally small or not, you do carry some of the DNA of some of those ancestors. It’s just broken into extremely small pieces today and their individual contributions to you may be extremely small. You don’t carry any DNA from some of them, actually, probably most of them, due to the recombination event, dividing their DNA in half, happening 800 times, give or take.
Now, given that your ancestors’ DNA is divided in every generation by approximately half, and we know there are about 3 billion base pairs on all of your chromosomes combined, this means that by generation 32 or 33, on average, you carry 1 segment from this ancestor. By generation 45, you carry, on average, .00017 segments of this ancestor’s DNA. And for those math aficionados among us, this is the mathematical notation for how much of our ancestor’s DNA we carry after 800 generations: 4.4991E-232.
But, we also know that this dividing in half, on the average, doesn’t always work exactly that way in reality, because some of those ancestors from 20,000 years ago did in fact pass their DNA to you, despite the infinitesimal odds against that happening. Some of their DNA was passed intact generation after generation, to you, and you carry it today. The DNA contributed by any one ancestor from 800 generations ago is probably limited to one or two locations, or bases, but still, it’s there, and it’s the combined DNA of those ancient ancestors that make us who we are today.
The autosomal DNA of any specific ancestor from long ago is probably too small and fragmented to recognize as “theirs” and attribute to them. Of course, the beauty of Y DNA and mitochondrial is that it is passed in tact for all of those generations. But for autosomal DNA and genealogy, we need hundreds of thousands of DNA pieces in a row from a particular ancestor to be recognizable as “theirs.” http://dna-explained.com/2013/08/05/autosomal-dna-ancient-ancestors-ethnicity-and-the-dandelion/
Direct Line paths of inheritance for both the Y-line, blue, and the mitochondrial DNA, red, are shown below. Contributions from the white genealogical lines may be small to nil, and dwindle quickly. Only men have the Y chromosome which is passed from father to son, usally along with the surname. Males carry their mother’s mitochondrial DNA (mtDNA) but they don’t pass it on. Mitochondrial DNA testing gives a haplogroup which defines deep ancestry, such as European, African, Asian or Native American, and percentages of ethnicity. Humans have 22 pairs of autosomes and one pair of sex chromosomes (the X and Y chromosomes).
Fifty percent of our autosomal DNA (atDNA) comes from our mother and 50% comes from our father. Since our parents each received 50% of their atDNA from each of their parents, we inherited about 25% of our atDNA from each of our grandparents. This percentage is cut in half with each generation as we go further up our family tree. We inherit about 12.5% of our atDNA from each great grandparent and about 6.25% from each of our 2nd great grandparents.
Autosomal DNA (not the 23rd chromosomal gender pair) tends to be transferred in groupings, which ultimately give us positive and negative family traits. Autosomal DNA is inherited from the autosomal chromosomes -- any of the numbered chromosomes, as opposed to the sex chromosomes. Only Autosomal DNA tests the rest of the DNA provided by both parents on the 23 chromosomes, not just two direct lines, as with Y-line and mitochondrial DNA. Autosomal inheritance paths include all of the various ancestral lines, including the lines that contribute the Y-line and mitochondrial line.
http://dna-explained.com/2012/10/01/4-kinds-of-dna-for-genetic-genealogy/
Ancient DNA
http://www.dailymail.co.uk/sciencetech/article-3432060/An-unknown-chapter-human-history-took-place-Europe-15-000-years-ago-DNA-shows-hunter-gatherers-replaced-mystery-group-people-Ice-Age.html
http://www.scientificamerican.com/article/a-surprise-source-of-life-s-code/
Genetic Genealogy
You don't have DNA from all or even most of your ancestors. About 360 years is just short of 15 generations. At 15 generations, an individual living today would carry only three thousands of 1% (00.003052%) of the DNA of an ancestor who was “pure” anything 15 generations ago. So even if one ancestor was indeed Mediterranean 15 generations ago, unless they continuously intermarried within a pure Mediterranean population, the amount would drop by 50% with each
generation to the miniscule amount that would be found in today’s current generation. With today’s technology, this is simply untraceable in autosomal DNA. An autosomal DNA test only goes back 8 generations. For genealogy within the most recent fifteen generations, STR markers help define paternal lineages.
We have about 43 genetic ancestors out of 1024 genealogical ancestors after 10 generations. The probability of having DNA from all of your genealogical ancestors at a particular generation becomes vanishingly small very rapidly; there is a 99.6% chance that you will have DNA from all of your 16 great-great grandparents, only a 54% of sharing DNA with all 32 of your G-G-G grandparents, and a 0.01% chance for your 64 G-G-G-G grandparents. You only have to go back 5 generations for genealogical relatives to start dropping off your DNA tree.
We also care about how many genetic ancestors we have after a certain number of generations: The number of genetic ancestors starts off growing exponentially, but eventually flattens out to around 125 (at 10 generations, 120 of your 1024 genealogical ancestors are genetic ancestors).
The percentage of DNA you would carry from a single ancestor who lived 20,000 years ago, assuming you only descended from that ancestor 1 time, is infinitesimally small. There are more zeroes following that decimal point than I have patience to type. Let’s call that ancestor Xenia and let’s say she is a female.However, you did inherit DNA from many of your ancestors who lived 20,000 years ago, thousands of them, because all of them, through their descendants, make up the DNA you carry today.
So infinitesimally small or not, you do carry some of the DNA of some of those ancestors. It’s just broken into extremely small pieces today and their individual contributions to you may be extremely small. You don’t carry any DNA from some of them, actually, probably most of them, due to the recombination event, dividing their DNA in half, happening 800 times, give or take.
Now, given that your ancestors’ DNA is divided in every generation by approximately half, and we know there are about 3 billion base pairs on all of your chromosomes combined, this means that by generation 32 or 33, on average, you carry 1 segment from this ancestor. By generation 45, you carry, on average, .00017 segments of this ancestor’s DNA. And for those math aficionados among us, this is the mathematical notation for how much of our ancestor’s DNA we carry after 800 generations: 4.4991E-232.
But, we also know that this dividing in half, on the average, doesn’t always work exactly that way in reality, because some of those ancestors from 20,000 years ago did in fact pass their DNA to you, despite the infinitesimal odds against that happening. Some of their DNA was passed intact generation after generation, to you, and you carry it today. The DNA contributed by any one ancestor from 800 generations ago is probably limited to one or two locations, or bases, but still, it’s there, and it’s the combined DNA of those ancient ancestors that make us who we are today.
The autosomal DNA of any specific ancestor from long ago is probably too small and fragmented to recognize as “theirs” and attribute to them. Of course, the beauty of Y DNA and mitochondrial is that it is passed in tact for all of those generations. But for autosomal DNA and genealogy, we need hundreds of thousands of DNA pieces in a row from a particular ancestor to be recognizable as “theirs.” http://dna-explained.com/2013/08/05/autosomal-dna-ancient-ancestors-ethnicity-and-the-dandelion/
Direct Line paths of inheritance for both the Y-line, blue, and the mitochondrial DNA, red, are shown below. Contributions from the white genealogical lines may be small to nil, and dwindle quickly. Only men have the Y chromosome which is passed from father to son, usally along with the surname. Males carry their mother’s mitochondrial DNA (mtDNA) but they don’t pass it on. Mitochondrial DNA testing gives a haplogroup which defines deep ancestry, such as European, African, Asian or Native American, and percentages of ethnicity. Humans have 22 pairs of autosomes and one pair of sex chromosomes (the X and Y chromosomes).
Fifty percent of our autosomal DNA (atDNA) comes from our mother and 50% comes from our father. Since our parents each received 50% of their atDNA from each of their parents, we inherited about 25% of our atDNA from each of our grandparents. This percentage is cut in half with each generation as we go further up our family tree. We inherit about 12.5% of our atDNA from each great grandparent and about 6.25% from each of our 2nd great grandparents.
Autosomal DNA (not the 23rd chromosomal gender pair) tends to be transferred in groupings, which ultimately give us positive and negative family traits. Autosomal DNA is inherited from the autosomal chromosomes -- any of the numbered chromosomes, as opposed to the sex chromosomes. Only Autosomal DNA tests the rest of the DNA provided by both parents on the 23 chromosomes, not just two direct lines, as with Y-line and mitochondrial DNA. Autosomal inheritance paths include all of the various ancestral lines, including the lines that contribute the Y-line and mitochondrial line.
http://dna-explained.com/2012/10/01/4-kinds-of-dna-for-genetic-genealogy/
Contained in the nucleus of each cell are twenty-three pairs of chromosomes. Twenty-two of these matched pairs of chromosomes are called "autosomes," while the 23rd pair determines your sex (male or female). Autosomal DNA is inherited from both parents, and includes random contributions from their parents, grandparents, and so on. Therefore, your autosomes essentially contain a complete genetic record, with all branches of your ancestry at some point contributing a piece of your autosomal DNA.
For each of your twenty-two pairs of autosomal chromosomes, you received one from your mother and one from your father. Before they passed these chromosomes down to you, the contents were randomly jumbled in a process called "recombination" (this is why you and your siblings are all a little different from each other). Your parents, in turn, received their chromosomes from their parents (your grandparents).
Your autosomal DNA, therefore, contains random bits of DNA from your great-grandparents, great-great grandparents, and so on.
Close relatives will share large fragments of DNA from a common ancestor. Connections arising from more distant relatives will result in smaller fragments of shared DNA. The smaller the fragment of shared autosomal DNA, generally the further back the connection in your family tree.
Even these tiny segments of shared DNA can potentially hold a clue, however! The way in which your individual DNA has recombined through the generations also means that you may no longer carry DNA from a particular ancestor. Distant relatives often share no genetic material at all, although it is also possible to match an individual through a very distant ancestor.
An autosomal DNA test surveys a person’s entire genome at over 700,000 locations. It covers both the maternal and paternal sides of the family tree, so it covers all lineages. The Y-DNA test only reflects the direct father-to-son path in your family tree, and the mtDNA test only reflects the direct mother-to-child path in your family tree.
For each of your twenty-two pairs of autosomal chromosomes, you received one from your mother and one from your father. Before they passed these chromosomes down to you, the contents were randomly jumbled in a process called "recombination" (this is why you and your siblings are all a little different from each other). Your parents, in turn, received their chromosomes from their parents (your grandparents).
Your autosomal DNA, therefore, contains random bits of DNA from your great-grandparents, great-great grandparents, and so on.
Close relatives will share large fragments of DNA from a common ancestor. Connections arising from more distant relatives will result in smaller fragments of shared DNA. The smaller the fragment of shared autosomal DNA, generally the further back the connection in your family tree.
Even these tiny segments of shared DNA can potentially hold a clue, however! The way in which your individual DNA has recombined through the generations also means that you may no longer carry DNA from a particular ancestor. Distant relatives often share no genetic material at all, although it is also possible to match an individual through a very distant ancestor.
An autosomal DNA test surveys a person’s entire genome at over 700,000 locations. It covers both the maternal and paternal sides of the family tree, so it covers all lineages. The Y-DNA test only reflects the direct father-to-son path in your family tree, and the mtDNA test only reflects the direct mother-to-child path in your family tree.
FOUNDER EFFECT
The founder effect is one way that nature can randomly create new species from existing populations. In this lesson, learn about the founder effect and how it can be seen in all humans across the globe.
In human genetics, Mitochondrial Eve is the matrilineal most recent common ancestor (MRCA), in a direct, unbroken, maternal line, of all currently living humans, who is estimated to have lived approximately 100,000–200,000 years ago.
The Logic Behind the Founder Effect
Think about the following scenario: A random group of ten men and ten women are suddenly stranded on a tropical island. Nineteen of the castaways have green eyes and one has blue eyes. The castaways decide that they have no chance of rescue, but they have plenty of supplies to start a new civilization. No outsiders ever find the island, but the civilization flourishes and many generations are born.
Now, consider this question: What color of eyes will most people on the island have? Considering that all but one of the original castaways had green eyes, you would be correct if you guessed that most of the descendants would likely have green eyes. You may not know the exact term for this phenomenon, but you have just demonstrated the logic behind what is known as the founder effect.
How the Founder Effect Works
A sequence of DNA that codes for a trait, such as eye color, is called a gene. Alleles are alternative forms of specific genes that are responsible for variations in a trait, such as green versus blue versus brown eyes. By examining the number of people that have each of these different eye colors, you can determine the frequency of the alleles in the population.
Occasionally, throughout history, small populations of a species have moved to an area that is sufficiently distant or physically isolated from the original population. This isolation prevents breeding between the two populations. By random chance alone, the allelic frequencies of one or more genes in the new population can be quite different than those of the original population.
This shift in allelic frequency due to the creation of a new, isolated population is called the founder effect. Using the example of eye color from above, if a small group of people with only green eyes is isolated on an island, the allelic frequency of green eyes in the new (founder) population will be much higher than that of the original (source) population.
The founder effect can occur during a migration if a small population moves sufficiently far from the home territory to prevent any interbreeding. The founder effect is also evident on islands. Small populations isolated on islands, arriving either via flight or floating on debris, can have different allelic frequencies simply by chance. If the founder population has alleles that impact their survival, either positively or negatively, evolution can lead to greater divergence between the two populations. Eventually, the founder population can become a new species, related to the original but unable to interbreed.
Examples of the Founder Effect
There are several classic examples of the founder effect. We'll start with the Pennsylvania Amish. In the 1700s, a small group (i.e., a founder population) of Europeans settled in Eastern Pennsylvania. Among this small group was an individual who carried an allele for Ellis-van Creveld syndrome. Ellis-van Creveld syndrome is a very rare form of dwarfism, causing short stature, extra fingers (known as polydactyly), abnormal teeth and nails, and heart defects. The allele for Ellis-van Creveld syndrome is found at a frequency of 7% in the Pennsylvania Amish in comparison to only 0.1% in the general population. The low allelic frequency of 0.1% was also the allelic frequency of the original European population from which the Amish migrated.
The higher allelic frequency in the Amish community is most likely due to the founder effect. While the Amish live in close proximity to large, diverse human populations that would be capable of breeding, the culture of the Amish restricts marriage outside of the group. This results in genetic isolation and group interbreeding that allows the frequency of the allele for Ellis-van Creveld syndrome to not only persist but increase over time.
Another example is the blood types of Native Americans. The original colonizers of the Americas most likely arrived by crossing the Bering Strait land bridge around 20,000 years ago and gradually moved south through North America and into South America. This founder population probably had many allelic variations from the original population.
While we have very little information on the allelic variation of the original population, today it is very rare to find a Native American with Type B blood. This suggests that in the founder population the occurrence or frequency of the Type B blood allele was very low. During much of the history of North America, until the arrival of the Europeans, the Native Americans, for the most part, would have been geographically isolated. This isolation, over thousands of years, resulted in the low frequency of Type B blood in Native Americans observed today.
Europeans with blue eyes are pretty closely related. Scientists can tell this by looking at their DNA.One piece of evidence is that most blue eyed Europeans share the exact same DNA difference that causes their blue eyes. Given that there are lots of ways to get blue eyes, this suggests that the people who share this DNA difference all came from the same original ancestor (or founder). By studying the DNA in a bit more detail, scientists have concluded that this original blue-eyed ancestor probably lived around 6,000-10,000 years ago.
It is important to note here that not everyone with the same trait is necessarily so closely related. For example, red haired Europeans get their red hair from a variety of DNA differences. Not all redheads can trace their history back to an original red haired ancestor.
Now the fact that blue eyes appeared out of nowhere isn’t that weird…our DNA is much less stable than a lot of people think. Changes in DNA (or mutations) can and do happen all the time so it isn’t surprising that occasionally one will happen in just the right place to cause blue eyes. This probably happened a number of times throughout human history.
No the weird part is that the blue eye mutation from that original ancestor took hold and spread through Europe. Usually this means that the mutation had to have an advantage. If it didn’t, then like most neutral mutations, it would stay at some low level or disappear entirely. But it is obviously still around and going strong.
http://www.livescience.com/42838-european-hunter-gatherer-genome-sequenced.html?li_source=LI&li_medium=more-from-livescience
http://www.livescience.com/37092-southern-europeans-have-african-genes.html?li_source=LI&li_medium=more-from-livescience
The founder effect is one way that nature can randomly create new species from existing populations. In this lesson, learn about the founder effect and how it can be seen in all humans across the globe.
In human genetics, Mitochondrial Eve is the matrilineal most recent common ancestor (MRCA), in a direct, unbroken, maternal line, of all currently living humans, who is estimated to have lived approximately 100,000–200,000 years ago.
The Logic Behind the Founder Effect
Think about the following scenario: A random group of ten men and ten women are suddenly stranded on a tropical island. Nineteen of the castaways have green eyes and one has blue eyes. The castaways decide that they have no chance of rescue, but they have plenty of supplies to start a new civilization. No outsiders ever find the island, but the civilization flourishes and many generations are born.
Now, consider this question: What color of eyes will most people on the island have? Considering that all but one of the original castaways had green eyes, you would be correct if you guessed that most of the descendants would likely have green eyes. You may not know the exact term for this phenomenon, but you have just demonstrated the logic behind what is known as the founder effect.
How the Founder Effect Works
A sequence of DNA that codes for a trait, such as eye color, is called a gene. Alleles are alternative forms of specific genes that are responsible for variations in a trait, such as green versus blue versus brown eyes. By examining the number of people that have each of these different eye colors, you can determine the frequency of the alleles in the population.
Occasionally, throughout history, small populations of a species have moved to an area that is sufficiently distant or physically isolated from the original population. This isolation prevents breeding between the two populations. By random chance alone, the allelic frequencies of one or more genes in the new population can be quite different than those of the original population.
This shift in allelic frequency due to the creation of a new, isolated population is called the founder effect. Using the example of eye color from above, if a small group of people with only green eyes is isolated on an island, the allelic frequency of green eyes in the new (founder) population will be much higher than that of the original (source) population.
The founder effect can occur during a migration if a small population moves sufficiently far from the home territory to prevent any interbreeding. The founder effect is also evident on islands. Small populations isolated on islands, arriving either via flight or floating on debris, can have different allelic frequencies simply by chance. If the founder population has alleles that impact their survival, either positively or negatively, evolution can lead to greater divergence between the two populations. Eventually, the founder population can become a new species, related to the original but unable to interbreed.
Examples of the Founder Effect
There are several classic examples of the founder effect. We'll start with the Pennsylvania Amish. In the 1700s, a small group (i.e., a founder population) of Europeans settled in Eastern Pennsylvania. Among this small group was an individual who carried an allele for Ellis-van Creveld syndrome. Ellis-van Creveld syndrome is a very rare form of dwarfism, causing short stature, extra fingers (known as polydactyly), abnormal teeth and nails, and heart defects. The allele for Ellis-van Creveld syndrome is found at a frequency of 7% in the Pennsylvania Amish in comparison to only 0.1% in the general population. The low allelic frequency of 0.1% was also the allelic frequency of the original European population from which the Amish migrated.
The higher allelic frequency in the Amish community is most likely due to the founder effect. While the Amish live in close proximity to large, diverse human populations that would be capable of breeding, the culture of the Amish restricts marriage outside of the group. This results in genetic isolation and group interbreeding that allows the frequency of the allele for Ellis-van Creveld syndrome to not only persist but increase over time.
Another example is the blood types of Native Americans. The original colonizers of the Americas most likely arrived by crossing the Bering Strait land bridge around 20,000 years ago and gradually moved south through North America and into South America. This founder population probably had many allelic variations from the original population.
While we have very little information on the allelic variation of the original population, today it is very rare to find a Native American with Type B blood. This suggests that in the founder population the occurrence or frequency of the Type B blood allele was very low. During much of the history of North America, until the arrival of the Europeans, the Native Americans, for the most part, would have been geographically isolated. This isolation, over thousands of years, resulted in the low frequency of Type B blood in Native Americans observed today.
Europeans with blue eyes are pretty closely related. Scientists can tell this by looking at their DNA.One piece of evidence is that most blue eyed Europeans share the exact same DNA difference that causes their blue eyes. Given that there are lots of ways to get blue eyes, this suggests that the people who share this DNA difference all came from the same original ancestor (or founder). By studying the DNA in a bit more detail, scientists have concluded that this original blue-eyed ancestor probably lived around 6,000-10,000 years ago.
It is important to note here that not everyone with the same trait is necessarily so closely related. For example, red haired Europeans get their red hair from a variety of DNA differences. Not all redheads can trace their history back to an original red haired ancestor.
Now the fact that blue eyes appeared out of nowhere isn’t that weird…our DNA is much less stable than a lot of people think. Changes in DNA (or mutations) can and do happen all the time so it isn’t surprising that occasionally one will happen in just the right place to cause blue eyes. This probably happened a number of times throughout human history.
No the weird part is that the blue eye mutation from that original ancestor took hold and spread through Europe. Usually this means that the mutation had to have an advantage. If it didn’t, then like most neutral mutations, it would stay at some low level or disappear entirely. But it is obviously still around and going strong.
The Gypsies (a misnomer, derived from an early legend about Egyptian origins) defy the conventional definition of a population: they have no nation-state, speak different languages, belong to many religions and comprise a mosaic of socially and culturally divergent groups separated by strict rules of endogamy. Referred to as “the invisible minority”, the Gypsies have for centuries been ignored by Western medicine, and their genetic heritage has only recently attracted attention. Common origins from a small group of ancestors characterise the 8–10 million European Gypsies as an unusual trans-national founder population, whose exodus from India played the role of a profound demographic bottleneck. Social and economic pressures within Europe led to gradual fragmentation, generating multiple genetically differentiated subisolates. The string of population bottlenecks and founder effects have shaped a unique genetic profile, whose potential for genetic research can be met only by study designs that acknowledge cultural tradition and self-identity. BioEssays 27:1084–1094, 2005. © 2005 Wiley Periodicals, Inc.
Founder populations are characterized by a single ancestor and by a large number of individuals and families who all are related to the ancestor and thereby carry the same disease-causing mutation.- A study by an international team suggests the central and eastern European Jewish population, known as Ashkenazi Jews, from whom most American Jews are descended, started from a founding population of about 350 people between 600 and 800 years ago. Further, that group of Jews who experienced this "bottleneck" was of approximately evenly mixed Middle Eastern and European descent. http://www.livescience.com/47755-european-jews-are-30th-cousins.html
http://www.livescience.com/42838-european-hunter-gatherer-genome-sequenced.html?li_source=LI&li_medium=more-from-livescience
http://www.livescience.com/37092-southern-europeans-have-african-genes.html?li_source=LI&li_medium=more-from-livescience
http://www.sott.net/article/310993-The-cells-of-our-ancestors-children-or-siblings-infiltrate-every-part-of-our-bodies
The cells of our ancestors, children or siblings infiltrate every part of our bodies
How's this for caring? Without being in the same room, building or even the same city as your mother, you can literally patch up her heart. Or your child can patch up yours. It's an idea that takes getting used to at first, but hear us out: you probably left tiny little bits of you inside your mother. And you got stuff from her, too: her cells take up residence in most of your organs, perhaps even your brain. They live there for years, decades even, meddling with your biology and your health.
Sure, your blood, skin, brain and lungs are made up of your own cells, but not entirely. Most of us are walking, talking patchworks of cells, with emissaries from our mother, children or even our siblings infiltrating every part of our bodies. Welcome to the bizarre world of microchimerism.
You are more than the sum of your cells. This idea came to prominence in mid-90s, when molecular biologist Richard Jefferson realised that the microbes inside and on us play an integral role in how healthy we are.
The idea emerged in the 1970s, when cells with male Y chromosomes were detected in the blood of pregnant women. Until then, we assumed that a mother's body and her child's were kept completely separate during pregnancy. Their blood came into close proximity in the placenta -- that large, messy bundle of blood vessels connecting mother and child via the umbilical cord -- but never actually mixed. Nutrients, oxygen and waste shuttled from one to the other through filters.
We now know that's only part of the story. "The placenta has been described as having a selective immigration policy," says Lee Nelson at the University of Washington in Seattle. Along with nutrients and waste, cells also move from one bloodstream to the other. In recent years, we've learned that these cells live on for years inside mother and child, as resident aliens. They lodge themselves inside our organs, so that long after birth, a mother's body is still in some way connected to her child's. The question is: what are these cells up to? Are they just passengers along for the ride, or do they get actively involved in the life of their host?
Spotting these "microchimeric" cells in the midst of billions of your own is a bit like looking for the proverbial needle in a haystack. To make matters worse, their number waxes and wanes in different organs, and they appear to move around the body. Depending on where you look, someone could appear microchimeric one day but not the next.
Staying power
Still, those who study this phenomenon believe the cells are an inextricable part of us. "If we were able to test lots of samples from multiple points in time and many different sources, we believe we would find microchimerism in most, if not all, individuals," says Nelson. "I would guess it is ubiquitous."
What is clear is that the cells get everywhere, have staying power and seem to be associated with both good and poor health. Earlier this year, a study of 26 women who died during pregnancy or within a month of giving birth found cells from their children in every organ tested, including the brain (see "Resident aliens"). Other research has shown that microchimeric cells can survive for 40 years. People who have more of these cells tend to be more prone to certain types of autoimmune disease, but have a lower risk of breast cancer and thyroid cancer, and may even be longer-lived. The trouble is that many of the earlier studies mainly looked at associations between the number of microchimeric cells in people and the incidence of disease. They stopped short of zooming in on what the cells are really up to.
That is now changing. At Mount Sinai Hospital in New York City, Hina Chaudhry studies a condition called peripartum cardiomyopathy, in which a pregnant woman's heart becomes weakened and enlarged. "Fifty per cent of women spontaneously recover, and no one knew why," says Chaudhry. The condition has the highest recovery rate of any form of heart failure.
To see if microchimeric cells from the fetus could be somehow coming to the mother's rescue, Chaudhry tagged mouse fetal cells with a green fluorescent tracer to track any that crossed into the mother mouse's bloodstream. Then she induced heart attacks in the pregnant mice. Sure enough, the fetal cells homed in on the damaged heart tissue where they turned into different types of heart cells. "It's fascinating: they know exactly where to go on their own," says Chaudhry.
Chaudhry's most recent studies have shown that a fetus provides a reservoir of embryonic stem cells to the mother. Trophoblast stem cells usually sit on the outer layer of the fetus. During pregnancy, they implant into the wall of the uterus and give rise to the placenta. In her pregnant mice, Chaudhry has found that it is these cells that make their way into the mother's bloodstream, race to the heart and form brand new beating muscle cells. She believes that the damaged heart tissue may release proteins that act as a beacon to the fetal cells. Her hope is that these studies may one day lead to stem cell therapies that treat different types of heart disease.
"Fetal cells race to the mother's heart and form brand new muscle cells"
Nelson is particularly interested in what fetal cells are doing in their mothers' brains. In 2012, she performed autopsies on the brains of 59 deceased women, and found that 63 per cent of them had signs of alien DNA. A 2005 study in mice found fetal cells turning into neurons in their mothers' brains. So could the same thing be happening in humans, helping to form the cells that carry information about your senses, your movement, your thoughts? Nelson and her team are now looking to see if this is the case and are expecting results in the next few months. They are also looking in the opposite direction, to see whether maternal cells reach the brains of their children. "I wouldn't be surprised if there were maternal cells in the brain," says Nelson, "and I wouldn't be surprised if they were an important part of normal development."
How microchimeric cells interact with our immune system is also a key point of interest. After all, the immune system is there to defend our bodies from invaders, yet microchimeric cells seem impervious to it. That's promising for things like organ transplants, but how do the cells dip below the immune system's radar? Nelson's colleague Hillary Gammill points out that microchimeric cells can turn into a type of immune cell: they literally embed themselves into our body's defences. Chaudhry is currently looking at the molecules on the surface of microchimeric cells to try to get to the bottom of this.
The health benefits and downsides may not be limited to mother and child. Gammill has looked at how a woman's cells could give a helping hand to the next generation when she becomes a grandmother. Pre-eclampsia is a complication seen in 6 per cent of pregnancies. In a study of women who developed the condition, Gammill found that none of them carried cells from their own mothers. By contrast nearly a third of the women in the study who didn't get pre-eclampsia did. Intriguingly, in these women, the number of their mother's cells in the blood got a boost during the pregnancy's third trimester, when pre-eclampsia is most common.
Protective hand
The results raise the intriguing possibility of some kind of protective hand being extended to the fetus from their grandmother, says Gammill. Jen Kotler at Harvard University is using the same green fluorescent tags as Chaudhry to trace cells across generations, and see whether cells from grandparents can end up in the brains of their grandchildren.
Why does microchimerism happen at all? Kotler's colleague David Haig points out that evolutionary pressures may be at play (see "You are multiple, but why?"). "You might expect that [fetal cells] will be enhancing bonding of the mother to the child," says Haig -- thus increasing the child's chance of survival. "We know there are changes in the brains of mice after pregnancy that are involved with the delivery of maternal care," says Haig (see "The real baby brain"). "We are raising the possibility that offspring cells could be having a say in the matter as well."
For Nelson, the weird world of microchimerism turns our understanding of the "biological self" on its head. "To me, the best working paradigm is that we are an ecosystem," she says, one made up of a patchwork of humans and which can have both positive and negative effects on our health. "Microchimeric cells are present in fairly low numbers, so that will tend to limit their influence," says Haig. "But small numbers of cells can have big influences. "
In future, we may be able to invite new helpful humans to join our body's ecosystem, and encourage less helpful ones to leave. Being human is about to get a whole lot more complicated.
Resident Aliens
Many organs in our bodies contain cells acquired from other people -- but what are they doing?
Brain Cells from fetuses make their way into the mother's brain. They have been found in several brain regions and may provide protection against Alzheimer's disease. They can turn into neurons in mice, but we don't yet know if the same happens in humans.
Lungs This organ holds more foreign cells than any other, possibly because it contains the first bed of capillaries that blood travels through after leaving the placenta. More blood also passes through the lungs than many other tissues. It has been speculated that microchimeric cells could carry out repairs here.
Breast Alien cells here have been linked to lower rates of breast cancer. Fetal cells could lengthen lactation and reduce the chances of a mother becoming pregnant again too soon after birth. Think of it as extreme sibling rivalry: the child's cells are preventing the conception of a new sibling who would sap the mother's time and energy.
Uterus Fetal cells have been found in the endometrium, the inner lining of the uterus, where they could interfere with the implantation of a new embryo. More sibling rivalry.
Heart Cells transferred from child to mother can repair her damaged heart tissue.
Skin A 2014 study found evidence that microchimeric cells help repair the body after a caesarean section. They are also often found in skin cancers, but further research is needed to discover whether they offer any protection.
The cells of our ancestors, children or siblings infiltrate every part of our bodies
How's this for caring? Without being in the same room, building or even the same city as your mother, you can literally patch up her heart. Or your child can patch up yours. It's an idea that takes getting used to at first, but hear us out: you probably left tiny little bits of you inside your mother. And you got stuff from her, too: her cells take up residence in most of your organs, perhaps even your brain. They live there for years, decades even, meddling with your biology and your health.
Sure, your blood, skin, brain and lungs are made up of your own cells, but not entirely. Most of us are walking, talking patchworks of cells, with emissaries from our mother, children or even our siblings infiltrating every part of our bodies. Welcome to the bizarre world of microchimerism.
You are more than the sum of your cells. This idea came to prominence in mid-90s, when molecular biologist Richard Jefferson realised that the microbes inside and on us play an integral role in how healthy we are.
The idea emerged in the 1970s, when cells with male Y chromosomes were detected in the blood of pregnant women. Until then, we assumed that a mother's body and her child's were kept completely separate during pregnancy. Their blood came into close proximity in the placenta -- that large, messy bundle of blood vessels connecting mother and child via the umbilical cord -- but never actually mixed. Nutrients, oxygen and waste shuttled from one to the other through filters.
We now know that's only part of the story. "The placenta has been described as having a selective immigration policy," says Lee Nelson at the University of Washington in Seattle. Along with nutrients and waste, cells also move from one bloodstream to the other. In recent years, we've learned that these cells live on for years inside mother and child, as resident aliens. They lodge themselves inside our organs, so that long after birth, a mother's body is still in some way connected to her child's. The question is: what are these cells up to? Are they just passengers along for the ride, or do they get actively involved in the life of their host?
Spotting these "microchimeric" cells in the midst of billions of your own is a bit like looking for the proverbial needle in a haystack. To make matters worse, their number waxes and wanes in different organs, and they appear to move around the body. Depending on where you look, someone could appear microchimeric one day but not the next.
Staying power
Still, those who study this phenomenon believe the cells are an inextricable part of us. "If we were able to test lots of samples from multiple points in time and many different sources, we believe we would find microchimerism in most, if not all, individuals," says Nelson. "I would guess it is ubiquitous."
What is clear is that the cells get everywhere, have staying power and seem to be associated with both good and poor health. Earlier this year, a study of 26 women who died during pregnancy or within a month of giving birth found cells from their children in every organ tested, including the brain (see "Resident aliens"). Other research has shown that microchimeric cells can survive for 40 years. People who have more of these cells tend to be more prone to certain types of autoimmune disease, but have a lower risk of breast cancer and thyroid cancer, and may even be longer-lived. The trouble is that many of the earlier studies mainly looked at associations between the number of microchimeric cells in people and the incidence of disease. They stopped short of zooming in on what the cells are really up to.
That is now changing. At Mount Sinai Hospital in New York City, Hina Chaudhry studies a condition called peripartum cardiomyopathy, in which a pregnant woman's heart becomes weakened and enlarged. "Fifty per cent of women spontaneously recover, and no one knew why," says Chaudhry. The condition has the highest recovery rate of any form of heart failure.
To see if microchimeric cells from the fetus could be somehow coming to the mother's rescue, Chaudhry tagged mouse fetal cells with a green fluorescent tracer to track any that crossed into the mother mouse's bloodstream. Then she induced heart attacks in the pregnant mice. Sure enough, the fetal cells homed in on the damaged heart tissue where they turned into different types of heart cells. "It's fascinating: they know exactly where to go on their own," says Chaudhry.
Chaudhry's most recent studies have shown that a fetus provides a reservoir of embryonic stem cells to the mother. Trophoblast stem cells usually sit on the outer layer of the fetus. During pregnancy, they implant into the wall of the uterus and give rise to the placenta. In her pregnant mice, Chaudhry has found that it is these cells that make their way into the mother's bloodstream, race to the heart and form brand new beating muscle cells. She believes that the damaged heart tissue may release proteins that act as a beacon to the fetal cells. Her hope is that these studies may one day lead to stem cell therapies that treat different types of heart disease.
"Fetal cells race to the mother's heart and form brand new muscle cells"
Nelson is particularly interested in what fetal cells are doing in their mothers' brains. In 2012, she performed autopsies on the brains of 59 deceased women, and found that 63 per cent of them had signs of alien DNA. A 2005 study in mice found fetal cells turning into neurons in their mothers' brains. So could the same thing be happening in humans, helping to form the cells that carry information about your senses, your movement, your thoughts? Nelson and her team are now looking to see if this is the case and are expecting results in the next few months. They are also looking in the opposite direction, to see whether maternal cells reach the brains of their children. "I wouldn't be surprised if there were maternal cells in the brain," says Nelson, "and I wouldn't be surprised if they were an important part of normal development."
How microchimeric cells interact with our immune system is also a key point of interest. After all, the immune system is there to defend our bodies from invaders, yet microchimeric cells seem impervious to it. That's promising for things like organ transplants, but how do the cells dip below the immune system's radar? Nelson's colleague Hillary Gammill points out that microchimeric cells can turn into a type of immune cell: they literally embed themselves into our body's defences. Chaudhry is currently looking at the molecules on the surface of microchimeric cells to try to get to the bottom of this.
The health benefits and downsides may not be limited to mother and child. Gammill has looked at how a woman's cells could give a helping hand to the next generation when she becomes a grandmother. Pre-eclampsia is a complication seen in 6 per cent of pregnancies. In a study of women who developed the condition, Gammill found that none of them carried cells from their own mothers. By contrast nearly a third of the women in the study who didn't get pre-eclampsia did. Intriguingly, in these women, the number of their mother's cells in the blood got a boost during the pregnancy's third trimester, when pre-eclampsia is most common.
Protective hand
The results raise the intriguing possibility of some kind of protective hand being extended to the fetus from their grandmother, says Gammill. Jen Kotler at Harvard University is using the same green fluorescent tags as Chaudhry to trace cells across generations, and see whether cells from grandparents can end up in the brains of their grandchildren.
Why does microchimerism happen at all? Kotler's colleague David Haig points out that evolutionary pressures may be at play (see "You are multiple, but why?"). "You might expect that [fetal cells] will be enhancing bonding of the mother to the child," says Haig -- thus increasing the child's chance of survival. "We know there are changes in the brains of mice after pregnancy that are involved with the delivery of maternal care," says Haig (see "The real baby brain"). "We are raising the possibility that offspring cells could be having a say in the matter as well."
For Nelson, the weird world of microchimerism turns our understanding of the "biological self" on its head. "To me, the best working paradigm is that we are an ecosystem," she says, one made up of a patchwork of humans and which can have both positive and negative effects on our health. "Microchimeric cells are present in fairly low numbers, so that will tend to limit their influence," says Haig. "But small numbers of cells can have big influences. "
In future, we may be able to invite new helpful humans to join our body's ecosystem, and encourage less helpful ones to leave. Being human is about to get a whole lot more complicated.
Resident Aliens
Many organs in our bodies contain cells acquired from other people -- but what are they doing?
Brain Cells from fetuses make their way into the mother's brain. They have been found in several brain regions and may provide protection against Alzheimer's disease. They can turn into neurons in mice, but we don't yet know if the same happens in humans.
Lungs This organ holds more foreign cells than any other, possibly because it contains the first bed of capillaries that blood travels through after leaving the placenta. More blood also passes through the lungs than many other tissues. It has been speculated that microchimeric cells could carry out repairs here.
Breast Alien cells here have been linked to lower rates of breast cancer. Fetal cells could lengthen lactation and reduce the chances of a mother becoming pregnant again too soon after birth. Think of it as extreme sibling rivalry: the child's cells are preventing the conception of a new sibling who would sap the mother's time and energy.
Uterus Fetal cells have been found in the endometrium, the inner lining of the uterus, where they could interfere with the implantation of a new embryo. More sibling rivalry.
Heart Cells transferred from child to mother can repair her damaged heart tissue.
Skin A 2014 study found evidence that microchimeric cells help repair the body after a caesarean section. They are also often found in skin cancers, but further research is needed to discover whether they offer any protection.
Some transgenerational consequences are epigenetic, regulated by triggers and on/off switches. Feedback determines whether epigenetic memory will continue to the progeny or not, and how long each epigenetic response will last. Specific genes called “MOTEK” (Modified Transgenerational Epigenetic Kinetics), are involved in turning epigenetic transmissions of small RNAs on and off. Manipulating genes in this feedback pathway changes the duration of heritable silencing. Such active control of transgenerational effects could be adaptive, since ancestral responses would be detrimental if the environments of the progeny and the ancestors were different.
http://www.kurzweilai.net/onoff-button-for-passing-along-epigenetic-memories-to-our-children-discovered
EPIGENETICS
Epigenetics: It doesn’t mean what quacks think it means
https://www.sciencebasedmedicine.org/epigenetics-it-doesnt-mean-what-quacks-think-it-means/
Whenever I see the hype over epigenetics (which, let’s face it, is not just a quack phenomenon—it’s just that the quacks take it beyond hype into magical thinking), one thing that always strikes me about it is that there is often a blending (or even confusing) of simple gene regulation compared to epigenetics. Proponents of epigenetics as the heart of all “efficacy” of CAM tend to exaggerate the potential benefits. Again, remember how they claim that epigenetics can completely overcome genetics. There’s really no good evidence. Less for branded 'epigenetic therapies'.
At the heart of this new field is a simple but contentious idea -- that genes have a 'memory'. That the lives of your grandparents -- the air they breathed, the food they ate, even the things they saw -- can directly affect you, decades later, despite your never experiencing these things yourself. And that what you do in your lifetime could in turn affect your grandchildren.
The conventional view is that DNA carries all our heritable information and that nothing an individual does in their lifetime will be biologically passed to their children. To many scientists, epigenetics amounts to a heresy, calling into question the accepted view of the DNA sequence -- a cornerstone on which modern biology sits.
Epigenetics adds a whole new layer to genes beyond the DNA. It proposes a control system of 'switches' that turn genes on or off -- and suggests that things people experience, like nutrition and stress, can control these switches and cause heritable effects in humans.
For example, a famine at critical times in the lives of the grandparents can affect the life expectancy of the grandchildren. This is the first evidence that an environmental effect can be inherited in humans.
Epigenetics is another crucial component to this puzzle, the knowledge of which has advanced a great deal in the past decade. We now know that the events and influences within a single animal’s life can be passed on to their offspring. Epigenetics is not a process that alters the actual DNA code but works, instead, through regulation of gene expression much like cell differentiation does. The reason we can have all the various cells of different organs appear from the single stem cell type is because of gene expression.
As one might expect, the sections of non-coding DNA which act in a regulatory role and impact the coding DNA have been found to be a part of the mechanism of epigenetics (Cao, J. 2014). These epigenetic changes can also, however, alter the likelihood that a real genetic mutation might occur in the affected area (Skinner 2015). The more short-term mechanisms of epigenetic change, when transmitted over longer trans-generational time scales, may, therefore, lead to direct genetic change.
The idea of genetic memory has been around for a very long time as an anecdotal conjecture. The ability of savants to know things it seems they have never learned has been explained in such a way, as have past life regressions etc. While the idea that instincts must exist as instructions hidden in genes which regulate brain morphology is widely assumed, these general instructions have generally been postulated to have formed purely through selection pressures.
With the recent understanding of epigenetics allowing for the experiences of a single individual to become heritable, the possibility of true genetic memory has become a scientifically viable area of inquiry. As such, a study was performed on mice in which parental traumatic exposure to cherry blossom scent passed down the fear conditioning to future generations in which even the grandchildren reacted very aversively toward the scent. Furthermore a gene was identified with sensitivity to that scent and changes to the expression of the gene had indeed been altered. Concurrent changes in brain structure were also observed in offspring (Dias & Ressler 2014).
Now that genetically transmitted memory is a scientifically validated concept, it is obvious that there is a data storage mechanism in DNA which interacts with mental experiences and it seems no large presumption that the interaction could possibly be two-way in nature.Might we then suppose that our non-coding DNA may be comprised of both trans-generational memories as well as a storehouse of more directly inserted information from long ago? Might the directly inserted older data play a role as a guiding principle for trans-generational memory and might those memories, built upon that original key, provide a sort of interpretational Rosetta stone for understanding that original information?
From a programming and engineering perspective, it makes sense to integrate the interpretational system in such a fashion.
In 2011 another new method of identifying spoken language emerged from the application of information theory in a novel fashion. While the “Shannon Entropy” (information density) of various languages differed, one aspect remained almost exactly the same across all languages. The amount of information carried by the structure of real communicative language is higher than a word-salad mix of words. When we take any text of any language and rearrange the words randomly, the amount of information per word decreases by the same amount regardless of language (Montemurro & Zanette 2011).
My personal opinion is that if non-coding DNA were subjected to this test, it would probably fail because the language of memories is likely more symbolic than syntax based. A reliance upon word ordering is usually reserved only for spoken language and not general data storage. Therefore a failure would not, in any way, falsify the library hypothesis. However, if this test were to come back positive, not only would the library hypothesis be utterly validated, but it would also likely mean that all genetic memory is encoded directly into the language once spoken by the ancients who created this library.
While this reliance upon syntax in the storage of genetic memory seems unlikely, it is not completely unsupported by scientific discoveries. Research at Carnegie Mellon has resulted in the discovery that language is stored so similarly from one human to the next, that the physical location in the brain for the data that represents nouns can be modeled and predicted by a computer.
Tests using fMRIs to read the blood flow and activation of these areas in the brain resulted in the ability to read a subject’s mind with between 70% and 94% accuracy when the subject focused upon a noun. The accuracy was so great that this computer-modeling-based “mind-reading” technique was able to distinguish between thoughts of extremely similar objects like “pliers” and “hammer.” (Mitchell et al 2008)
While this is not a reliance upon word ordering, it shows a standardization of language storage from one human to the next. Therefore the concept of storing additional information by the relationships between words is not necessarily a large leap, but is a worthy area of future inquiry. It does, however, lend itself to a representational mechanism, based upon physical position, by which genetic memory may be encoded. Specifically, it provides a structural system by which one language may be translated into a different one.
https://grahamhancock.com/meuccis1/
Multigenerational Epigenetics
In psychology, genetic memory is a memory present at birth that exists in the absence of sensory experience, and is incorporated into the genome over long spans of time. It is based on the idea that common experiences of a species become incorporated into its genetic code, not by a Lamarckian process that encodes specific memories but by a much vaguer tendency to encode a readiness to respond in certain ways to certain stimuli. Shares much with the modern concept of epigenetics.
Genetic memory is invoked to explain ethnic group memory postulated by Carl Jung. Jungian psychology suggests memories, feelings and ideas inherited from our ancestors as part of a "collective unconscious". The term "epigenetic" refers to heritable traits that do not involve changes to the underlying DNA sequence. This can occur over rounds of cell division, while some epigenetic features can effect transgenerational inheritance and are inherited from one generation to the next.
Multigenerational epigenetics is today regarded as another aspect to evolution and adaptation. Culture is the most fundamental force that has shaped man's life through the aeons. Its effect is, in all likelihood, established in the genome in a few generations.The concept implies that genes have a 'memory'; what you do in your lifetime, and what you are exposed to, could in turn affect your grandchildren.
Epigenetics adds a whole new layer to genes beyond the DNA, the so called "epigenome". Among other things, it proposes a control system of 'switches' that turn genes on or off. The things that people experience, like nutrition and stress, can control these switches and cause heritable effects in humans. The switches themselves can also be inherited. This means that a 'memory' of an event could be passed through generations. A simple environmental effect could switch genes on or off - and this change could be inherited.
Epigenetics can impact evolution when epigenetic changes are heritable.[1] A sequestered germ line or Weismann barrier is specific to animals, and epigenetic inheritance is more common in plants and microbes. Eva Jablonka and Marion Lamb have argued that these effects may require enhancements to the standard conceptual framework of the modern evolutionary synthesis.[97][98] Other evolutionary biologists have incorporated epigenetic inheritance into population genetics models[99] or are openly skeptical.[100]
Two important ways in which epigenetic inheritance can be different from traditional genetic inheritance, with important consequences for evolution, are that rates of epimutation can be much faster than rates of mutation[101] and the epimutations are more easily reversible.[102] In plants heritable DNA methylation mutations are 100.000 times more likely to occur compared to DNA mutations.[103] An epigenetically inherited element such as the PSI+ system can act as a "stop-gap", good enough for short-term adaptation that allows the lineage to survive for long enough for mutation and/or recombination to genetically assimilate the adaptive phenotypic change.[104] The existence of this possibility increases the evolvability of a species.
More than 100 cases of transgenerational epigenetic inheritance phenomena have been reported in a wide range of organisms, including prokaryotes, plants, and animals.[105] For instance, Mourning Cloak butterflies will change color through hormone changes in response to experimentation of varying temperatures.[106] Bacteria make widespread use of postreplicative DNA methylation for the epigenetic control of DNA-protein interactions. Bacteria make use of DNA adenine methylation (rather than DNA cytosine methylation) as an epigenetic signal. DNA adenine methylation is important in bacteria virulence in organisms such as Escherichia coli, Salmonella, Vibrio, Yersinia, Haemophilus, and Brucella. In Alphaproteobacteria, methylation of adenine regulates the cell cycle and couples gene transcription to DNA replication. In Gammaproteobacteria, adenine methylation provides signals for DNA replication, chromosome segregation, mismatch repair, packaging of bacteriophage, transposase activity and regulation of gene expression.[107][108]
The filamentous fungus Neurospora crassa is a prominent model system for understanding the control and function of cytosine methylation. In this organisms, DNA methylation is associated with relics of a genome defense system called RIP (repeat-induced point mutation) and silences gene expression by inhibiting transcription elongation.[109]
The yeast prion PSI is generated by a conformational change of a translation termination factor, which is then inherited by daughter cells. This can provide a survival advantage under adverse conditions. This is an example of epigenetic regulation enabling unicellular organisms to respond rapidly to environmental stress. Prions can be viewed as epigenetic agents capable of inducing a phenotypic change without modification of the genome.[108]
Direct detection of epigenetic marks in microorganisms is possible with single molecule real time sequencing, in which polymerase sensitivity allows for measuring methylation and other modifications as a DNA molecule is being sequenced.[110] Several projects have demonstrated the ability to collect genome-wide epigenetic data in bacteria.[111][112][113][114]
https://en.wikipedia.org/wiki/Epigenetics
http://www.uleth.ca/unews/article/researchers-show-prenatal-stress-influences-new-behavioural-traits-including-handedness
“Ancestral stress often affects males more than females,” says Ambeskovic. “It affects their behaviour and it also changes their brain organization, so we see the structural changes in the neurons and their spine density.”
Researchers don’t know what comes first, paw preference or a dominant right brain hemisphere but even so, such changes should be adaptive. Ambeskovic says ancestral stress may have a protective effect for females.
“It could be that, through epigenetics, our moms prepare us for a stressful environment that might be coming down the road and it’s more important for females to know how to cope with it as they will be the bearers of the future generation,” says Ambeskovic.
In the same way, males affected by ancestral stress might be better prepared to defend their territory because they are more adaptable, perhaps because they could be more prone to using both paws if needed, Metz adds.
“There have been studies, that for programming across generations, there’s an increase in behavioural flexibility, especially in the males. That’s what we’re seeing here. There’s more flexibility to do more tasks,” says Metz.
Ambeskovic is also looking at the effects of multigenerational stress and aging. She has found that males exposed to multigenerational stress are more susceptible to chronic diseases as they age. This study, and others, show the brain can be changed by experience and this could help pave the way to developing interventions that could change the brain in beneficial ways earlier in life.
http://www.uleth.ca/unews/article/researchers-show-prenatal-stress-influences-new-behavioural-traits-including-handedness
Seven thousand five hundred fifty-six (7556) haplotypes of 46 subclades in 17 major haplogroups were considered in terms of their base (ancestral) haplotypes and timespans to their common ancestors, for the purposes of designing of time-balanced haplogroup tree. It was found that African haplogroup A (originated 132,000 ± 12,000 years before present) is very remote time-wise from all other haplogroups, which have a separate common ancestor, named β-haplogroup, and originated 64,000 ± 6000 ybp. It includes a family of Europeoid (Caucasoid) haplogroups from F through T that originated 58,000 ± 5000 ybp. A downstream common ancestor for haplogroup A and β-haplogroup, coined the α-haplogroup emerged 160,000 ± 12,000 ybp. A territorial origin of haplogroups α- and β-remains unknown; however, the most likely origin for each of them is a vast triangle stretched from Central Europe in the west through the Russian Plain to the east and to Levant to the south. Haplogroup B is descended from β-haplogroup (and not from haplogroup A, from which it is very distant, and separated by as much as 123,000 years of “lat- eral” mutational evolution) likely migrated to Africa after 46,000 ybp. The finding that the Europeoid haplogroups did not descend from “African” haplogroups A or B is supported by the fact that bearers of the Europeoid haplogroups, as well as all non-African haplogroups do not carry either SNPs M91, P97, M31, P82, M23, M114, P262, M32, M59, P289, P291, P102, M13, M171, M118 (haplogroup A and its subclades SNPs) or M60, M181, P90 (haplogroup B), as it was shown recently in “Walk through Y” FTDNA Project (the reference is incorporated therein) on several hundred people from various haplogroups.
Klyosov, A. & Rozhanskii, I. (2012). Re-Examining the "Out of Africa" Theory and the Origin of Europeoids (Caucasoids) in Light of DNA Genealogy. Advances in Anthropology, 2, 80-86. doi: 10.4236/aa.2012.22009.
http://www.scirp.org/journal/PaperInformation.aspx?paperID=19566
Among his fellow Russian, (and other),
researchers Klyosov is considered a whack job. Here is an excerpt from a
biodiversity forum:"Vadim Verenich
2012-03-26, 16:04
To put it briefly, Klyosov's "arguments" in a nutshell:
This garbage, non-science was "published" by a discredited Russian ultra-nationalist (with a reputation for being a ding-bat), claiming that all humans outside Africa did not originate in Africa but actually originated in a "vast triangle" between, wait for it, _Russia_, The Levant and Central Europe. Except that it was *not* actually published; certainly not in a genuine, accredited, peer-reviewed scientific journal. It was merely "put on the internet" through a medium that will post any garbage dependent only on the author's willingness to pay. Thus, the garbage in that paper was doubtless rejected by many journals until the authors decided to pay SciRP.org, a thoroughly scurrilous and disreputable heap of shit, whatever fee they were demanding. SciRP.org is *so* disreputable that the entire editorial board of _Advances in Anthropology_ resigned in protest, _en masse_, in 2014.
You only have to read the paper in that e-rag to see that the conclusions are spurious and misleading, even without any previous, in-depth knowledge of Y haplotypes. One obvious error (or fraud) is that they talk about the African haplogroup as if it is virtually monomorphic, when anyone with even the vaguest knowledge of the subject knows that the San bushmen population in Southern Africa has the greatest degree of Y haplotype variation on the entire planet.
This paper is very far from genuine science and constitutes actual scientific fraud.
Klyosov, A. & Rozhanskii, I. (2012). Re-Examining the "Out of Africa" Theory and the Origin of Europeoids (Caucasoids) in Light of DNA Genealogy. Advances in Anthropology, 2, 80-86. doi: 10.4236/aa.2012.22009.
http://www.scirp.org/journal/PaperInformation.aspx?paperID=19566
Among his fellow Russian, (and other),
researchers Klyosov is considered a whack job. Here is an excerpt from a
biodiversity forum:"Vadim Verenich
2012-03-26, 16:04
To put it briefly, Klyosov's "arguments" in a nutshell:
This garbage, non-science was "published" by a discredited Russian ultra-nationalist (with a reputation for being a ding-bat), claiming that all humans outside Africa did not originate in Africa but actually originated in a "vast triangle" between, wait for it, _Russia_, The Levant and Central Europe. Except that it was *not* actually published; certainly not in a genuine, accredited, peer-reviewed scientific journal. It was merely "put on the internet" through a medium that will post any garbage dependent only on the author's willingness to pay. Thus, the garbage in that paper was doubtless rejected by many journals until the authors decided to pay SciRP.org, a thoroughly scurrilous and disreputable heap of shit, whatever fee they were demanding. SciRP.org is *so* disreputable that the entire editorial board of _Advances in Anthropology_ resigned in protest, _en masse_, in 2014.
You only have to read the paper in that e-rag to see that the conclusions are spurious and misleading, even without any previous, in-depth knowledge of Y haplotypes. One obvious error (or fraud) is that they talk about the African haplogroup as if it is virtually monomorphic, when anyone with even the vaguest knowledge of the subject knows that the San bushmen population in Southern Africa has the greatest degree of Y haplotype variation on the entire planet.
This paper is very far from genuine science and constitutes actual scientific fraud.
Deep within your DNA, a tiny parasite lurks, waiting to pounce from its perch and land in the middle of an unsuspecting healthy gene. If it succeeds, it can make you sick.
Like a jungle cat, this parasite sports a long tail. But until now, little was known about what role that tail plays in this dangerous jumping.
Today, scientists report that without a tail, this parasitic gene can't jump efficiently. The findings could help lead to new strategies for inhibiting the movement of the parasite, called a LINE-1 retrotransposon.
The research, published in Molecular Cell by a team from the University of Michigan Medical School and the Howard Hughes Medical Institute, answers a key question about how "jumping genes" move to new DNA locations.
The parasite in question isn't a foreign beast, but rather a piece of DNA that carries its own instructions for making a piece of "rogue" genetic material and two proteins that can help it jump. "Jumping" allows this rogue copy to land anywhere in the DNA of a cell, causing a change called a mutation.
Jumping LINE-1s - and other genetic parasites like it - are responsible for about one in every 250 disease producing mutations in humans. They've been blamed for causing a number of diseases, including hemophilia, Duchenne muscular dystrophy, and cancer. Copies of this parasite litter our DNA, though most of them can no longer jump and cause damage.
For these reasons, scientists want to understand as much as possible about how this process works. Perhaps someday, this new understanding could help fight the effects of these jumps - or prevent the parasites from leaping in the first place.
"Now, we have a mechanism to explain how sequences that comprise one-third of our genome have moved," says John Moran, Ph.D., senior author of the new paper and a longtime U-M and HHMI researcher studying jumping genes. "By understanding how LINE-1 jumps, we can understand how it contributes to disease."
A cat without a tail, a tail without a cat
The gene that's responsible for LINE-1 jumping does its damage by first creating an RNA copy of itself. That RNA copy tells the cell to make two proteins that help make it possible for the LINE-1 RNA itself to jump into a new spot.
Each copy of LINE-1 RNA has a long tail at its end that's made up of multiple copies of a substance called adenosine. Known as a "poly(A) tail", it's long been suspected of playing a role in LINE-1 jumping. But it was impossible to figure this role out because removing the tail also eliminates another key function it serves, in getting the RNA to the location where proteins are made.
Like the Cheshire Cat of Alice in Wonderland, if the tail vanished, the rest of the "cat" would too.
So, a postdoctoral fellow, Aurélien Doucet, Ph.D., now a research associate at the Institute for Research on Cancer and Aging in Nice, or CNRS, in France, collaborated with Jeremy Wilusz, Ph.D., now an assistant professor at the University of Pennsylvania Perelman School of Medicine, to figure out a way to delete the LINE-1 poly(A) tail to determine if it affected LINE-1 jumping.
They succeeded in making a LINE-1 RNA, without a poly(A) tail, that got where it needed to in the cell to make proteins.
The substitute tail allowed the scientists to see what happened when LINE-1 RNA could get to the protein-making spot, but without its usual appendage.
Here's where it gets interesting. Without the poly(A) tail, almost no jumping happened - because the tailless LINE-1 RNA couldn't interact well with a protein called ORF2p.
ORF2p is actually one of the two proteins that the LINE-1 RNA tells the cell to make. Once ORF2p binds to the RNA's tail, it sets in motion the steps needed for a jump to occur.
Moran compares it to a Lego set - where one kind of tail could get unplugged and another slotted in to serve some, but not all, of the same functions.
In other words, the LINE-1 parasite is especially crafty.
A parasite of a parasite?
LINE-1 also has a competitor parasite, called Alu. And when LINE-1 RNA lacked the tail and couldn't jump, Alu RNA did much better at jumping.
Alu RNA also sports a poly(A) sequence at its end, which has already been shown to be vital to its ability to jump. But the Alu RNA doesn't contain the instructions for making a protein. This suggests, says Moran, that the two parasites compete to have access to ORF2p proteins. That is, Alu is a parasite of a parasite.
Moran and his team continue to build on their new finding that poly(A) sequences are crucial for retrotransposition. They're studying how Alu interacts with ORF2p, and how the use of a replacement for the poly(A) tail may be helpful in other research. They're also interested in how the cell, or host, fights off jumping genes and protects DNA from damage.
"Our DNA is a sea of junk copies of LINE-1 that can't jump, and a small minority of LINE-1s that can," says Moran, who is the Gilbert S. Omenn Collegiate Professor of Human Genetics in the U-M Department of Human Genetics. "We need to understand at the RNA level how these LINE-1 RNAs are chosen for jumping, and how we can stop them."
http://phys.org/news/2015-11-parasite-tail-team-gene-mystery.html?utm_content=buffer39119&utm_medium=social&utm_source=facebook.com&utm_campaign=buffer
Like a jungle cat, this parasite sports a long tail. But until now, little was known about what role that tail plays in this dangerous jumping.
Today, scientists report that without a tail, this parasitic gene can't jump efficiently. The findings could help lead to new strategies for inhibiting the movement of the parasite, called a LINE-1 retrotransposon.
The research, published in Molecular Cell by a team from the University of Michigan Medical School and the Howard Hughes Medical Institute, answers a key question about how "jumping genes" move to new DNA locations.
The parasite in question isn't a foreign beast, but rather a piece of DNA that carries its own instructions for making a piece of "rogue" genetic material and two proteins that can help it jump. "Jumping" allows this rogue copy to land anywhere in the DNA of a cell, causing a change called a mutation.
Jumping LINE-1s - and other genetic parasites like it - are responsible for about one in every 250 disease producing mutations in humans. They've been blamed for causing a number of diseases, including hemophilia, Duchenne muscular dystrophy, and cancer. Copies of this parasite litter our DNA, though most of them can no longer jump and cause damage.
For these reasons, scientists want to understand as much as possible about how this process works. Perhaps someday, this new understanding could help fight the effects of these jumps - or prevent the parasites from leaping in the first place.
"Now, we have a mechanism to explain how sequences that comprise one-third of our genome have moved," says John Moran, Ph.D., senior author of the new paper and a longtime U-M and HHMI researcher studying jumping genes. "By understanding how LINE-1 jumps, we can understand how it contributes to disease."
A cat without a tail, a tail without a cat
The gene that's responsible for LINE-1 jumping does its damage by first creating an RNA copy of itself. That RNA copy tells the cell to make two proteins that help make it possible for the LINE-1 RNA itself to jump into a new spot.
Each copy of LINE-1 RNA has a long tail at its end that's made up of multiple copies of a substance called adenosine. Known as a "poly(A) tail", it's long been suspected of playing a role in LINE-1 jumping. But it was impossible to figure this role out because removing the tail also eliminates another key function it serves, in getting the RNA to the location where proteins are made.
Like the Cheshire Cat of Alice in Wonderland, if the tail vanished, the rest of the "cat" would too.
So, a postdoctoral fellow, Aurélien Doucet, Ph.D., now a research associate at the Institute for Research on Cancer and Aging in Nice, or CNRS, in France, collaborated with Jeremy Wilusz, Ph.D., now an assistant professor at the University of Pennsylvania Perelman School of Medicine, to figure out a way to delete the LINE-1 poly(A) tail to determine if it affected LINE-1 jumping.
They succeeded in making a LINE-1 RNA, without a poly(A) tail, that got where it needed to in the cell to make proteins.
The substitute tail allowed the scientists to see what happened when LINE-1 RNA could get to the protein-making spot, but without its usual appendage.
Here's where it gets interesting. Without the poly(A) tail, almost no jumping happened - because the tailless LINE-1 RNA couldn't interact well with a protein called ORF2p.
ORF2p is actually one of the two proteins that the LINE-1 RNA tells the cell to make. Once ORF2p binds to the RNA's tail, it sets in motion the steps needed for a jump to occur.
Moran compares it to a Lego set - where one kind of tail could get unplugged and another slotted in to serve some, but not all, of the same functions.
In other words, the LINE-1 parasite is especially crafty.
A parasite of a parasite?
LINE-1 also has a competitor parasite, called Alu. And when LINE-1 RNA lacked the tail and couldn't jump, Alu RNA did much better at jumping.
Alu RNA also sports a poly(A) sequence at its end, which has already been shown to be vital to its ability to jump. But the Alu RNA doesn't contain the instructions for making a protein. This suggests, says Moran, that the two parasites compete to have access to ORF2p proteins. That is, Alu is a parasite of a parasite.
Moran and his team continue to build on their new finding that poly(A) sequences are crucial for retrotransposition. They're studying how Alu interacts with ORF2p, and how the use of a replacement for the poly(A) tail may be helpful in other research. They're also interested in how the cell, or host, fights off jumping genes and protects DNA from damage.
"Our DNA is a sea of junk copies of LINE-1 that can't jump, and a small minority of LINE-1s that can," says Moran, who is the Gilbert S. Omenn Collegiate Professor of Human Genetics in the U-M Department of Human Genetics. "We need to understand at the RNA level how these LINE-1 RNAs are chosen for jumping, and how we can stop them."
http://phys.org/news/2015-11-parasite-tail-team-gene-mystery.html?utm_content=buffer39119&utm_medium=social&utm_source=facebook.com&utm_campaign=buffer
Ancient DNA shows Stone Age humans
evolved quickly as they took up farming
By Joel Achenbach November 23
People in western Eurasia underwent evolutionary changes as they adopted farming as a way of life.
Prehistoric people who adopted farming as a way of life underwent evolutionary changes to adapt to their new lifestyle, a dramatic example of natural selection operating on the human species in the relatively recent past.
That's one of the conclusions of a new study of the genomes of 230 individuals who lived thousands of years ago and whose bones have been recovered from Western Eurasia — a broad area that includes what is now Turkey, the Russian Steppe and Europe.
The research, published Monday in the journal Nature, identified 12 specific genetic mutations that corresponded to the rise of agriculture and the migration of people into new regions. They include the ability to digest milk and metabolize fats. The mutations also favored greater height at maturity, lighter skin and lighter eye color in northern populations. There are also genetic markers that appear to be connected to resistance against such diseases as leprosy and tuberculosis.
Ancient DNA shows Stone Age humans evolved quickly as they took up farming
By Joel Achenbach
Prehistoric people who adopted farming as a way of life underwent evolutionary changes to adapt to their new lifestyle, a dramatic example of natural selection operating on the human species in the relatively recent past.
That's one of the conclusions of a new study of the genomes of 230 individuals who lived thousands of years ago and whose bones have been recovered from Western Eurasia — a broad area that includes what is now Turkey, the Russian Steppe and Europe.
The research, published Monday in the journal Nature, identified 12 specific genetic mutations that corresponded to the rise of agriculture and the migration of people into new regions. They include the ability to digest milk and metabolize fats. The mutations also favored greater height at maturity, lighter skin and lighter eye color in northern populations. There are also genetic markers that appear to be connected to resistance against such diseases as leprosy and tuberculosis.
swer to the question of how agriculture arrived in Europe. There have been two competing scenarios. One is that agricultural people — farmers — arrived as migrants, replacing indigenous populations. The other is the practices of farming were transmitted culturally, a contagion of innovation known to anthropologists as "cultural diffusion."
The new research strongly supports the first scenario, showing that the people who began farming in Europe, starting about 8,500 years ago, were closely connected to a population of farmers in Anatolia, a region that largely overlaps with modern-day Turkey.
“It is a migration. It’s a movement of people. The farmers in Europe from Germany and Spain are genetically almost identical to the farmers from Turkey," said Iain Mathieson, a geneticist at Harvard Medical School and the lead author of the new report.
[Research shows Stone Age farmers and hunters didn't mingle]
Modern human beings spent many tens of thousands of years as hunters and gatherers. But at the end of the last Ice Age, as temperatures stabilized, people in Mesopotamia and the Levant — the Fertile Crescent — began planting crops and domesticating animals as livestock. The farmers and their new way of life spread to other parts of Eurasia. Farming allowed greater population density, but it was a difficult way of life that at first led to poor nutrition and zoonotic diseases associated with living in close quarters with domesticated animals.
[The switch to farming made our skeletons more fragile (because we got lazier)]
“It's a change in the food people are eating. It’s a change in social organization. People are living in much bigger communities. People are living in much closer proximity to animals," Mathieson said.
That was a technological revolution that had genetic repercussions. Natural selection functions as a filter, favoring people with certain genetic mutations that allow them to more easily reach maturity and have children who are themselves advantaged. Thus, around 4,000 years ago, according to the new study, Europeans begun showing a genetic change associated with lactase persistence — the ability to digest milk into adulthood.
That such evolutionary changes have been taking place in the relatively recent past is not a surprise. Indeed, scientists have modeled many of these genetic adaptions simply by looking at people alive today and comparing their genomes. But this new work is more of a direct look at the prehistoric evolutionary processes as they were happening.
“It's taking ancient DNA to actually go back in the past," said Rasmus Nielsen, an evolutionary biologist at the University of California at Berkeley. He was not part of the team that published the new findings. "The paper is able to verify many of the predictions that have been done in the past 20 years from looking at modern populations. In some sense we have this scientific time machine," he said.
One possible implication of this research is that the popular "Paleo Diet," which embraces foods available to Stone Age people and avoids the dairy products and grains that came along only in the last 10,000 years, ignores the recent evolutionary changes in the human species. But Mathieson did not take a stance on this latest food fad.
"I don't think we can really speak to this," he said. "We show that people were able to adapt genetically to an agricultural diet, but it's rather an open question how well they adapted."
evolved quickly as they took up farming
By Joel Achenbach November 23
People in western Eurasia underwent evolutionary changes as they adopted farming as a way of life.
Prehistoric people who adopted farming as a way of life underwent evolutionary changes to adapt to their new lifestyle, a dramatic example of natural selection operating on the human species in the relatively recent past.
That's one of the conclusions of a new study of the genomes of 230 individuals who lived thousands of years ago and whose bones have been recovered from Western Eurasia — a broad area that includes what is now Turkey, the Russian Steppe and Europe.
The research, published Monday in the journal Nature, identified 12 specific genetic mutations that corresponded to the rise of agriculture and the migration of people into new regions. They include the ability to digest milk and metabolize fats. The mutations also favored greater height at maturity, lighter skin and lighter eye color in northern populations. There are also genetic markers that appear to be connected to resistance against such diseases as leprosy and tuberculosis.
Ancient DNA shows Stone Age humans evolved quickly as they took up farming
By Joel Achenbach
Prehistoric people who adopted farming as a way of life underwent evolutionary changes to adapt to their new lifestyle, a dramatic example of natural selection operating on the human species in the relatively recent past.
That's one of the conclusions of a new study of the genomes of 230 individuals who lived thousands of years ago and whose bones have been recovered from Western Eurasia — a broad area that includes what is now Turkey, the Russian Steppe and Europe.
The research, published Monday in the journal Nature, identified 12 specific genetic mutations that corresponded to the rise of agriculture and the migration of people into new regions. They include the ability to digest milk and metabolize fats. The mutations also favored greater height at maturity, lighter skin and lighter eye color in northern populations. There are also genetic markers that appear to be connected to resistance against such diseases as leprosy and tuberculosis.
swer to the question of how agriculture arrived in Europe. There have been two competing scenarios. One is that agricultural people — farmers — arrived as migrants, replacing indigenous populations. The other is the practices of farming were transmitted culturally, a contagion of innovation known to anthropologists as "cultural diffusion."
The new research strongly supports the first scenario, showing that the people who began farming in Europe, starting about 8,500 years ago, were closely connected to a population of farmers in Anatolia, a region that largely overlaps with modern-day Turkey.
“It is a migration. It’s a movement of people. The farmers in Europe from Germany and Spain are genetically almost identical to the farmers from Turkey," said Iain Mathieson, a geneticist at Harvard Medical School and the lead author of the new report.
[Research shows Stone Age farmers and hunters didn't mingle]
Modern human beings spent many tens of thousands of years as hunters and gatherers. But at the end of the last Ice Age, as temperatures stabilized, people in Mesopotamia and the Levant — the Fertile Crescent — began planting crops and domesticating animals as livestock. The farmers and their new way of life spread to other parts of Eurasia. Farming allowed greater population density, but it was a difficult way of life that at first led to poor nutrition and zoonotic diseases associated with living in close quarters with domesticated animals.
[The switch to farming made our skeletons more fragile (because we got lazier)]
“It's a change in the food people are eating. It’s a change in social organization. People are living in much bigger communities. People are living in much closer proximity to animals," Mathieson said.
That was a technological revolution that had genetic repercussions. Natural selection functions as a filter, favoring people with certain genetic mutations that allow them to more easily reach maturity and have children who are themselves advantaged. Thus, around 4,000 years ago, according to the new study, Europeans begun showing a genetic change associated with lactase persistence — the ability to digest milk into adulthood.
That such evolutionary changes have been taking place in the relatively recent past is not a surprise. Indeed, scientists have modeled many of these genetic adaptions simply by looking at people alive today and comparing their genomes. But this new work is more of a direct look at the prehistoric evolutionary processes as they were happening.
“It's taking ancient DNA to actually go back in the past," said Rasmus Nielsen, an evolutionary biologist at the University of California at Berkeley. He was not part of the team that published the new findings. "The paper is able to verify many of the predictions that have been done in the past 20 years from looking at modern populations. In some sense we have this scientific time machine," he said.
One possible implication of this research is that the popular "Paleo Diet," which embraces foods available to Stone Age people and avoids the dairy products and grains that came along only in the last 10,000 years, ignores the recent evolutionary changes in the human species. But Mathieson did not take a stance on this latest food fad.
"I don't think we can really speak to this," he said. "We show that people were able to adapt genetically to an agricultural diet, but it's rather an open question how well they adapted."