Razib Khan One-stop-shopping for all of my content

April 23, 2017

The logic of human destiny was inevitable 1 million years ago

Filed under: Evolution,Genetics,Genomics,Human Evolution,Human Genetics — Razib Khan @ 1:11 pm

Robert Wright’s best book, Nonzero: The Logic of Human Destiny, was published near 20 years ago. At the time I was moderately skeptical of his thesis. It was too teleological for my tastes. And, it does pander to a bias in human psychology whereby we look to find meaning in the universe.

But this is 2017, and I have somewhat different views.

In the year 2000 I broadly accepted the thesis outlined a few years later in The Dawn of Human Culture. That our species, our humanity, evolved and emerged in rapid sequence, likely due to biological changes of a radical kind, ~50,000 years ago. This is the thesis of the “great leap forward” of behavioral modernity.

Today I have come closer to models proposed by Michael Tomasello in The Cultural Origins of Human Cognition and Terrence Deacon in The Symbolic Species: The Co-evolution of Language and the Brain. Rather than a punctuated event, an instance in geological time, humanity as we understand it was a gradual process, driven by general dynamics and evolutionary feedback loops.

The conceit at the heart of Robert J. Sawyer’s often overly preachy Neanderthal Parallax series, that if our own lineage went extinct but theirs did not they would have created a technological civilization, is I think in the main correct. It may not be entirely coincidental that the hyper-drive cultural flexibility of African modern humans evolved in African modern humans first. There may have been sufficient biological differences to enable this to be likely. But I believe that if African modern humans were removed from the picture Neanderthals would have “caught up” and been positioned to begin the trajectory we find ourselves in during the current Holocene inter-glacial.

Luke Jostins’ figure showing across board encephalization

The data indicate that all human lineages were subject to increased encephalization. That process trailed off ~200,000 years ago, but it illustrates the general evolutionary pressures, ratchets, or evolutionary “logic”, that applied to all of them. Overall there were some general trends in the hominin lineage that began to characterized us about a million years ago. We pushed into new territory. Our rate of cultural change seems to gradually increased across our whole range.

One of the major holy grails I see now and then in human evolutionary genetics is to find “the gene that made us human.” The scramble is definitely on now that more and more whole genome sequences from ancient hominins are coming online. But I don’t think there will be such gene ever found. There isn’t “a gene,” but a broad set of genes which were gradually selected upon in the process of making us human.

In the lingo, it wasn’t just a hard sweep from a de novo mutation. It was as much, or even more, soft sweeps from standing variation.

April 4, 2017

How Tibetans can function at high altitudes

Filed under: Altitude Adaptation,Evolution,Genetics,Genomics,Human Evolution,Tibetans — Razib Khan @ 11:10 am


About seven years ago I wrote two posts about how Tibetans manage to function at very high altitudes. And it’s not just physiological functioning, that is, fitness straightforwardly understood. High altitudes can cause a sharp reduction in reproductive fitness because women can not carry pregnancies to term. In other words, high altitude is a very strong selection pressure. You adapt, or you die off.

For me there have been two things of note since those original papers came out. First, one of those loci seem to have been introgressed from a Denisovan genetic background. I want to be careful here, because the initial admixture event may not have been into the Tibetans proper, but earlier hunter-gatherers who descend from Out of Africa groups, who were assimilated into the Tibetans as they expanded 5-10,000 years ago. Second, it turns out that dogs have been targeted for selection on EPAS1 as well (the “Denisovan” introgression) for altitude adaptation as well.

This shows that in mammals at least there’s a few genes which show up again and again. The fact that EPAS1 and EGLN1 were hits on relatively small sample sizes also reinforces their powerful effect. When the EPAS1 results initially came out they were highlighted as the strongest and fastest instance of natural selection in human evolutionary history. One can quibble about the details about whether this was literally true, but that it was a powerful selective event no one could deny.

A new paper in PNAS, Genetic signatures of high-altitude adaptation in Tibetans, revisits the earlier results with a much larger sample size (the research group is in China) comparing Han Chinese and Tibetans. They confirm the earlier results, but, they also find other loci which seem likely targets of selection in Tibetans. Below is the list:

SNP A1 A2 Frequency of A1 P value FST Nearest gene
Tibetan EAS (Han)
rs1801133 A G 0.238 0.333 6.30E-09 0.021 MTHFR
rs71673426 C T 0.102 0.013 1.50E-08 0.1 RAP1A
rs78720557 A T 0.498 0.201 4.70E-08 0.191 NEK7
rs78561501 A G 0.599 0.135 6.10E-15 0.414 EGLN1
rs116611511 G A 0.447 0.003 3.60E-19 0.57 EPAS1
rs2584462 G A 0.211 0.549 3.90E-09 0.203 ADH7
rs4498258 T A 0.586 0.287 1.70E-08 0.171 FGF10
rs9275281 G A 0.095 0.365 1.10E-10 0.162 HLA-DQB1
rs139129572 GA G 0.316 0.449 5.80E-09 0.036 HCAR2
P value indicates the P value from the MLMA-LOCO analysis. FST is the FST value between Tibetans and EASs. Nearest gene indicates the nearest annotated gene to the top differentiated SNP at each locus except EGLN1, which is known to be associated with high-altitude adaptation; rs139129572 is an insertion SNP with two alleles: GA and G. A1, allele 1; A2, allele 2.

Many of these genes are familiar. Observe the allele frequency differences between the Tibetans and other East Asians (mostly Han). The sample sizes are on the order of thousands, and the SNP-chip had nearly 300,000 markers. What they found was that the between population Fst of Han to Tibetan was ~0.01. So only 1% of the SNP variance in their data was partitioned between the two groups. These alleles are huge outliers.

The authors used some sophisticated statistical methods to correct for exigencies of population structure, drift, admixture, etc., to converge upon these hits, but even through inspection the deviation on these alleles is clear. And as they note in the paper it isn’t clear all of these genes are selected simply for hypoxia adaptation. MTFHR, which is quite often a signal of selection, may have something to due to folate production (higher altitudes have more UV). ADH7 is part of a set of genes which always seem to be under selection, and HLA is never a surprise.

Rather than get caught up in the details it is important to note here that expansion into novel habitats results in lots of changes in populations, so that two groups can diverge quite fast on functional characteristics.  The PCA makes it clear that Tibetans and Hans have very little West Eurasian admixture, and the Fst based analysis puts their divergence on the order of 5,000 years before the present. The authors admit honestly that this is probably a lower bound value, but I also think it is quite likely that Tibetans, and probably Han too, are compound populations, and a simple bifurcation model from a common ancestral population is probably shaving away too many realistic edges. In plainer language, there has been gene flow between Han and Tibetans probably <5,000 years ago, and Tibetans themselves probably assimilated more deeply diverged populations in the highlands as they expanded as agriculturalists. An estimate of a single divergence fits a complex history to too simple of a model quite often.

The take home: understanding population history is probably important to get a better sense of the dynamics of adaptation.

Citation: Jian Yang, Zi-Bing Jin, Jie Chen, Xiu-Feng Huang, Xiao-Man Li, Yuan-Bo Liang, Jian-Yang Mao, Xin Chen, Zhili Zheng, Andrew Bakshi, Dong-Dong Zheng, Mei-Qin Zheng, Naomi R. Wray, Peter M. Visscher, Fan Lu, and Jia Qu, Genetic signatures of high-altitude adaptation in Tibetans, PNAS 2017 ; published ahead of print April 3, 2017, doi:10.1073/pnas.1617042114

October 21, 2012

The arcane art of ancient admixture

Filed under: Anthroplogy,Human Evolution,Human Genetics — Razib Khan @ 9:29 pm


I have mentioned the PLoS Genetics paper, The Date of Interbreeding between Neandertals and Modern Humans, before because a version of it was put up on arXiv. The final paper has a few additions. For example, it mentions the generally panned (at least in the circles I run in) PNAS paper which suggested that ancient population structure could produce the same patterns which were earlier used to infer admixture with Neandertals (the authors also point to Yang et al. as a support for the proposition of admixture rather than structure). The primary result, dating the admixture between Neandertals and anatomically modern humans ~40-80,000 years before the present, is reiterated.

An interesting aspect is that their method is to utilize linkage disequilibrium (LD) decay. It’s interesting because tens of thousands of years is a hell of a long time to be able to detect an admixture event via LD! In particular because there’s likely a palimpsest effect where there are intervening admixtures and other assorted demographic events (e.g., bottlenecks and selective sweeps can also generate LD). So how’d they do it? Basically the authors figured out a way to ...

October 16, 2012

Neandertal one stop shopping

Filed under: Human Evolution,Neandertals — Razib Khan @ 11:46 pm

If you have a hard time following all the Neandertal genomics findings from the last few years, and their implications, National Geographic has a really thorough piece up. It’s a good digest of all the news you can use. One thing I would like to add: from what I can tell the probability of the signals of admixture in non-Africans being genuinely Neandertal seem to be increasing as we progress. In other words, you should weight the “other side” (ancient population structure, where some African populations were closer to Neandertals before they left Africa) less than you did in 2010.

Of course one of the more inevitable aspects of the admixture story has been the humanization of Neandertals. I don’t know how I feel about this. Should our own affinity to Neandertals alter our view of their behavior or anatomy? Plenty of behaviorally anatomically modern humans were beastly after all.

October 15, 2012

Don’t trust an archaeologist about genetics, don’t trust a geneticist about archaeology

Filed under: Anthroplogy,Evolutionary Genetics,Human Evolution — Razib Khan @ 1:38 pm

Who to trust? That is the question when you don’t know very much (all of us). Trust is precious, and to some extent sacred. That’s why I can flip out when I realize after the fact that someone more informed than me in field X sampled biased their argument in a way they knew was shady to support a proposition they were forwarding. What’s the point of that? Who cares if you win at a particular bull-session? You’re burning through cultural capital. And not that most of my interlocutors care, but I’m likely to never trust them again on anything.

In any case, this came to mind when I ran across a James Fallows’ post at The Atlantic. Here’s a screenshot of the appropriate section, with my underlines:


The PNAS link is wrong. The correspondent is actually linking to an article in Quaternary International. And they do point out that there are possible problems with draft quality sequences due to contamination. But I didn’t find the paper too persuasive. There are two issues. First, the Denisova genome is very good quality. So you can be more ...

October 12, 2012

I believe in the blank slate!

Filed under: Anthroplogy,Human Evolution — Razib Khan @ 11:21 am

Well, not really…but in some ways close enough judged against the initial reference point of where I started on certain questions. Dienekes contends:

This will help us understand both: the ancestors of non-Africans did not come forth fully formed, like Athena from Zeus’s head, having spent millennia of perfecting their craft and honing their minds by perforating shells and scratching lines in some South African cave. Instead, they may been plain old-style hunter-gatherers who stumbled into Asia by doing what they always did: following the food. At the same time, the UP/LSA revolution may not have been effected by a new and improved type of human bursting into the scene and replacing Neandertals and assorted dummies, but rather as a cultural revolution that spread across a species that already had the genetic potential for it, and was already firmly established in both Africa and Asia.

The former position, that the Out-of-Africa population were genetically endowed supermen who blitzkrieged other humans ~50,000 years ago was probably the most common position ~10 years ago. It’s outlined by Richard Klein in The Dawn of Human Culture. A contrasting argument was put forth at about the same time by Stephen Oppenheimer in

I believe in the blank slate!

Filed under: Anthroplogy,Human Evolution — Razib Khan @ 11:21 am

Well, not really…but in some ways close enough judged against the initial reference point of where I started on certain questions. Dienekes contends:

This will help us understand both: the ancestors of non-Africans did not come forth fully formed, like Athena from Zeus’s head, having spent millennia of perfecting their craft and honing their minds by perforating shells and scratching lines in some South African cave. Instead, they may been plain old-style hunter-gatherers who stumbled into Asia by doing what they always did: following the food. At the same time, the UP/LSA revolution may not have been effected by a new and improved type of human bursting into the scene and replacing Neandertals and assorted dummies, but rather as a cultural revolution that spread across a species that already had the genetic potential for it, and was already firmly established in both Africa and Asia.

The former position, that the Out-of-Africa population were genetically endowed supermen who blitzkrieged other humans ~50,000 years ago was probably the most common position ~10 years ago. It’s outlined by Richard Klein in The Dawn of Human Culture. A contrasting argument was put forth at about the same time by Stephen Oppenheimer in

I believe in the blank slate!

Filed under: Anthroplogy,Human Evolution — Razib Khan @ 11:21 am

Well, not really…but in some ways close enough judged against the initial reference point of where I started on certain questions. Dienekes contends:

This will help us understand both: the ancestors of non-Africans did not come forth fully formed, like Athena from Zeus’s head, having spent millennia of perfecting their craft and honing their minds by perforating shells and scratching lines in some South African cave. Instead, they may been plain old-style hunter-gatherers who stumbled into Asia by doing what they always did: following the food. At the same time, the UP/LSA revolution may not have been effected by a new and improved type of human bursting into the scene and replacing Neandertals and assorted dummies, but rather as a cultural revolution that spread across a species that already had the genetic potential for it, and was already firmly established in both Africa and Asia.

The former position, that the Out-of-Africa population were genetically endowed supermen who blitzkrieged other humans ~50,000 years ago was probably the most common position ~10 years ago. It’s outlined by Richard Klein in The Dawn of Human Culture. A contrasting argument was put forth at about the same time by Stephen Oppenheimer in

October 10, 2012

There may be no gene which is essential for our humanity

Filed under: Anthroplogy,Human Evolution — Razib Khan @ 11:39 pm

The always informative Ann Gibbons has a piece in Slate, The Neanderthal in My Family Tree. There is almost nothing new for regular readers of this weblog, but it’s rather awesome that Slate is now publishing stuff like this. Many people are simply unaware of the new paleogenomics. Case in point, a good friend who has a doctorate in chemical physics, and was totally unaware a year after the seminal Science paper on Neandertal admixture of the likelihood of Neandertal admixture!

Nevertheless, I think it is important for me to be repetitive and highlight a disagreement I have with the Gibbons’ piece. She says:

…But the differences in the genomes of Denisovans, Neanderthals, and modern humans are also revealing the genetic traits that set us apart from them—the traits that made us human. “I’ve been comparing it to the pictures of Earth that came back from Apollo 8. The Neanderthal genome gives us a picture of ourselves, from the outside looking in,” says paleoanthropologist John Hawks of the University of Wisconsin in Madison, in his blog on paleoanthropology, genetics, and evolution. “We can see, and now learn about, the essential genetic changes that make us human—the things that made ...

September 29, 2012

The Others, in black and white

Filed under: Anthroplogy,Human Evolution — Razib Khan @ 12:18 am

New Scientist has a piece up, Europeans did not inherit pale skins from Neanderthals, based on a paper I blogged last month. One thing that I hadn’t though about in detail…how did anatomically modern humans of various shades perceive Neandertals of various shades? For example, it seems highly likely that there were swarthy Neandertals and pale Neandertals. Similarly, there were swarthy modern humans, and soon enough pale ones. Skin color is a very salient trait. Very different populations phylogenetically, Sub-Saharan Africans, Melanesians, and South Asians, have been defined as “black.” Did modern humans perceive Middle Eastern Neandertals, who may have been relatively dark, as much closer to humanlike status because of their similar complexion to anatomically modern Middle Eastern humans? Did they perceive European Neandertals, who may on average have been much lighter, as fundamentally different?

When doing physical reconstructions it seems to me that the gross morphology of Neandertals has been more emphasized. Their brow ridges, large prominent noses, and stocky body plans. But in this manner perhaps they’re like our imaginings of ancient Greek temples as alabaster white. In reality the temples of antiquity and many public buildings were festooned with color. Similarly, Neandertals came in all shades.

September 23, 2012

Humanity isn’t, it becomes

Filed under: Anthroplogy,Human Evolution,Neandertals — Razib Khan @ 6:55 pm

John Hawks prompts to reemphasize an aspect of my thinking which has undergone a revolution over the past 10 years. I pointed to it in my post on the Khoe-San. In short, the common anatomically modern human ancestors of Khoe-San and non-Khoe-San may not have been people. Rather, people may have evolved over the past 100-200,000 years ago. Of course the term “people” is not quite as scientific as you might like. In philosophy and law you have debates about “personhood”. Granting the utility of these debates I am basically saying that the common ancestor of Khoe-San and non-Khoe-San may not have been persons, as well understand them. Though, as a person myself, I do think they were persons. At this point I am willing to push the class “person” rather far back in time.

As I suggested earlier there is an implicit assumption that personhood is a shared derived trait of our species. Or at least it is a consensus today that all extant members of H. sapiens are persons. Since Khoe-San are persons, the common ancestor of Khoe-San and non-Khoe-San must also be ...

September 18, 2012

The brambly bush of humanity

Over at Haldane’s Sieve there are more than preprints posted, there are commentaries from the authors as well. For example, for The genetic prehistory of southern Africa, the first author, Dr. Joseph K. Pickrell, has a extended comment up.

But occasionally you get contributions & perspectives from non-authors which are very interesting. And it is to one of these I want to draw your attention, Thoughts on: The date of interbreeding between Neandertals and modern humans. It’s a comment on The date of interbreeding between Neandertals and modern humans. In the post Dr. Graham Coop contends:

At this point you are likely saying: well we know that Neandertals existed as a [somewhat] separate population/species who are these population X you keep talking about and where are their remains? Population X could easily be a subset of what we call Neandertals, in which case you’ve been reading this all for no reason [if you only want to know if we interbred with Neandertals]. However, my view is that in the next decade of ancient human population history things are going to get really interesting. We have already seen this from the Denisovian papers [1,2], and the work ...

September 3, 2012

The pruned tree

Filed under: Anthroplogy,Human Evolution — Razib Khan @ 9:45 pm

Dienekes Pontikos has a long post up on how reticulation within phylogenetic trees may distort our perception of human natural history when we force the data into a more conventional tree (i.e., bifurcation after bifurcation). The concrete reason for this rethinking is the high probability of “archaic admixture” into the dominant genetic signal of anatomically modern African humanity, both within Africa and outside of it.

Dienekes proposes that when ancient DNA from early modern Eurasians is analyzed then a large portion of the portrait will be unmasked. For example, if high levels of admixture were present very early on then you would see very divergent regional populations because of persistence and continuity of local hominin population substructure. The pre-African Eurasians from each given region would have contributed substantially to the genetic makeup of the first modern humans who flourished in Europe and East Asia. On the other hand, if admixture was minimal, then the early Europeans and Asians would be far less distinct than their modern descents.

This is where I want to highlight one aspect of Dienekes’ model which is implicit, but I think needs to be strongly emphasized. ...

August 28, 2012

Not all genes are created the same

The map to the right shows the frequencies of HGDP populations on SLC45A2, which is a locus that has been implicated in skin color variation in humans. It’s for the SNP rs16891982, and I yanked the figure from IrisPlex: A sensitive DNA tool for accurate prediction of blue and brown eye colour in the absence of ancestry information. Brown represents the genotype CC, green CG, and blue, GG. Europeans who have olive skin often carry the minor allele, C. While SLC24A5 is really bad at distinguishing West Eurasians from each other, SLC45A2 is better. Though both are fixed in Northern Europe, the former stays operationally fixed in frequency outside of Europe, in the Near East. As I stated earlier the proportions of the ancestral SNP in the Middle Eastern populations in the HGDP seem to be easily explained by the Sub-Saharan admixture you can find in these groups.

In contrast major SNPs in SLC45A2 are closer to disjoint between Europeans and South Asians. For example I’m a homozygote for the C allele. And yet even here we need ...

August 27, 2012

Europeans got less shaded in stages

The Pith: the evolution of lighter skin is complex, and seems to have occurred in stages. The current European phenotype may date to the end of the last Ice Age.

A new paper in Molecular Biology and Evolution, The timing of pigmentation lightening in Europeans, is rather interesting. It’s important because skin pigmentation has been one of the major successes of the first age of human genomics. In 2002 we really didn’t know the nature of normal human variation in skin color in terms of specific genes (basically, we knew about MC1R). This is what Armand Leroi observed in Mutants in 2005, wondering about our ignorance of such a salient trait. Within a few years though Leroi’s contention was out of date (in fact, while Mutants was going to press it became out of date) . Today we do know the genetic architecture of pigmentation. This is why GEDmatch can predict that my daughter’s eyes will be light brown from just her SNPs (they are currently hazel). This genomic yield was facilitated by the fact that pigmentation seems to be a trait where most human variation is ...

August 26, 2012

Eat smarter, don’t work out harder?

Filed under: Anthroplogy,Human Evolution — Razib Khan @ 4:53 pm

There have been several recent studies reemphasizing diet over exercise (timely because Americans are kind of fat, on average). A new piece in The New York Times looking at the Hadza of Tanzania, who are hunter-gatherers, seems to reiterate this point, Debunking the Hunter-Gatherer Workout:

We found that despite all this physical activity, the number of calories that the Hadza burned per day was indistinguishable from that of typical adults in Europe and the United States. We ran a number of statistical tests, accounting for body mass, lean body mass, age, sex and fat mass, and still found no difference in daily energy expenditure between the Hadza and their Western counterparts.

How can the Hadza be more active than we are without burning more calories? It’s not that their bodies are more efficient, allowing them to do more with less: separate measurements showed that the Hadza burn just as many calories while walking or resting as Westerners do.

We think that the Hadzas’ bodies have adjusted to the higher activity levels required for hunting and gathering by spending less energy elsewhere. Even for very active people, physical activity accounts for only a small portion of daily energy expenditure; most energy is ...

August 19, 2012

On phylogenetic instrumentalism

Filed under: Genomics,Human Evolution,Human Genetics,Human Genomics,phylogenetics — Razib Khan @ 4:40 pm

ADMIXTURE and STRUCTURE tests aren’t formal mixture tests. Yes! In fact, in the “open science” community this issue is repeated over and over and over, because people routinely get confused (our audience does not consist of population geneticists and phylogeneticists by and large). So sometimes it is necessary to lay it out in detail as in the post above. The key point to always remember is that population genetic & phylogenetic statistics and visualizations are a reduction and summary of reality in human palatable form. They tell us something, but they do not tell us everything. A common issue is that for purposes of mental digestion it is useful to label ancestral elements “European,” or on PCA refer to a “European-Asian” cline, as if the population genetic abstractions themselves are the measure of what European or Asian is. But European and Asian are themselves human constructions, and subject to debate (e.g., do Turks count as Europeans? Indians as Asians?) The population genetic statistics are not themselves subjective, but the meanings we give them are.


Let’s illustrate this with a concrete example. The Cape Coloured population of South Africa is a compound of Khoisan, Bantu, South Asian, Southeast Asian, and ...

August 18, 2012

The origins of modern humanity: 2012

Filed under: Anthroplogy,Human Evolution — Razib Khan @ 5:26 pm

Matt Ridley has a column up, Did Your Ancestor Date a Neanderthal? In it he juxtaposes the two recent papers which got some attention on the relationship of modern humans to Neandertals. To be frank I think it took too much of the “two sides/opposing views/views differ” tack. From what I can gather the scientific consensus is moving further toward admixture, rather than ancient structure. Additionally, as John Hawks states flat out the PNAS paper which casts doubt on the strength of the admixture hypothesis is not the strongest of contributions to the field(in line with David Reich and Nick Patterson’s assessments, and others who shall remain nameless).

But it’s hard to keep track of all the threads, isn’t it? One of the most tragic aspects of the death of classic “Out of Africa” is that we lost an exceedingly simple narrative which had the positives of clarity and precision. The basic outlines were reducible to one sentence: all humans today descend from a small group of modern humans alive ~100,000 years ago. At this time we do not have such an elegant replacement framework. In fact, we may never have such an elegant model which ...

August 14, 2012

Neanderthal admixture & the ecology of academe

Yesterday I pointed out that David Reich had a moderately dismissive attitude toward the new paper in PNAS, Effect of ancient population structure on the degree of polymorphism shared between modern human populations and ancient hominins. Here’s what Reich said:

…But Reich believes that the discussion would have been different if it had happened in the open. The PNAS paper questioning the Neanderthal admixture addresses issues swirling around two years ago, but not Reich and Slatkin’s latest work. “It’s been an issue for several years. They were right to work on this,” says Reich. But now, “it’s kind of an obsolete paper,” he says.

Here’s what Nick Patterson, Reich’s colleague told me via email:

Ancient structure in Africa was considered when we wrote the Green et al. paper, and we were aware that this could explain D-statistics. But the hypothesis is no longer viable as the major explanation of Neandertal genetics in Eurasia. This was discussed in the recent paper of Yang et al. (MBE, 2012). (Not referenced by the PNAS paper).

A very simple argument, that convinces me, is that the allelic frequency spectrum of Neandertal alleles in Eurasia falls off very quickly. A bottleneck flattens out the ...

August 12, 2012

Human-on-human sex

Filed under: Human Evolution,Neandertal — Razib Khan @ 11:27 pm

Dienekes tips me off to the fact that the long-awaited Reich lab paper on Neandertal admixture dating has finally been put on arXiv! The date of interbreeding between Neandertals and modern humans:

Comparisons of DNA sequences between Neandertals and present-day humans have shown that Neandertals share more genetic variants with non-Africans than with Africans. This could be due to interbreeding between Neandertals and modern humans when the two groups met subsequent to the emergence of modern humans outside Africa. However, it could also be due to population structure that antedates the origin of Neandertal ancestors in Africa. We measure the extent of linkage disequilibrium (LD) in the genomes of present-day Europeans and find that the last gene flow from Neandertals (or their relatives) into Europeans likely occurred 37,000-86,000 years before the present (BP), and most likely 47,000-65,000 years ago. This supports the recent interbreeding hypothesis, and suggests that interbreeding may have occurred when modern humans carrying Upper Paleolithic technologies encountered Neandertals as they expanded out of Africa.

This isn’t the only group working on the Neandertal genomic admixture story. From reading his blog you probably know that John Hawks is working in this area, but there are other ...

Older Posts »

Powered by WordPress