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

February 27, 2019

The world is more than two categories

Filed under: GSS,Identity Politics — Razib Khan @ 11:22 pm

A post from Kevin Drum, Once Again, a New Book Debunks Some History I Never Knew In the First Place,* made me wonder a few things. First, Kevin’s confusion:

Am I befuddled by history? Or by historiography? Or do I need a different word altogether?

Until five minutes ago, before I read this book review, it never would have occurred to me that white women were anything less than full partners with men in the white supremacy of the antebellum South. I have never read anything that even remotely suggests such a thing. And yet, apparently this has been a widely held belief—and not just by the masses, but by practicing historians as well.

Additionally, today I listened to the Extremeley Offline podcast where Zaid Jilani moderated a conversation between Liz Bruenig and Jon Chait, and Jilani talks about some of his confusion and discomfort with the racial dichotomies that have recently emerged in the United States (though our politics are very different it seems we have had the same experiences and reactions in relation to this). For example, all nonwhites are now “people of color,” set against whites. The three present a thesis that a dominant form of conceptualization of the world on the modern Left is between the marginalized and those who are not, and so you have dichotomies. People of color vs. whites. Women vs. men. The queer vs. straight. And, of course, the poor vs. the rich.

Which brings me back to Drum’s observation: as an older white male of a certain generation I don’t think he’s internalized the dichotomous framework intuitively. Within that framework, the idea that white women were oppressed, just like black people, in the South by white men, may lead to the idea that there should be and is natural solidarity among the marginalized. Presumably in a “progressive stack” white males would be on top and black females at the bottom. But white females and black males would be in the middle.

Reality is of course not line with the simplicity of this framework. Men, women, blacks, and whites, do not exist in a simple individualized world where their interactions are all dyadic and governed by heuristics of power. White women are part of families and communities, and during the antebellum South, those families and communities were invested in the institution of slavery. White women reflected, reinforced, and even shaped, some of their subculture’s values. They were subordinates. But they were invested in the system, not simply humans from which production could be extracted before their expiration.

To illustrate this complexity, consider differences in attitudes toward laws regarding interracial marriage in the United States. The chart above shows responses from the GSS for whites only by year. What you notice is that there is almost no difference between men and women. Doing a logit regression sex does not predict different attitudes at all. Men and women show the same support/opposition to these laws over the years.

But, this does not mean that men and women are the same in their attitudes on a conventional liberal/progressive spectrum. I did a second analysis of attitudes toward gay marriage. Women are consistently less opposed to gay marriage (again I limited the sample to whites). When I did a logit regression sex remained a very significant predictive variable (though less so than education and political ideology).

Basically, when it comes to racial issues men and women do not seem to differ much in their attitude. In some revealed attitudes, such as dating, women seem somewhat more racially conservative than men. But, when it comes to attitudes toward gays and rights for gays, women have generally been somewhat more liberal than men.

The moral of the story is than Manichaean ideological frameworks are great for tactical mobilization of coalitions. But they don’t easily reflect a simple calculus of moral attitudes, affinities, and sympathies.

* It’s very rare that one of my posts mentions another blog post on another blog nowadays. Very nostalgic.

The Insight Show Notes — Season 2, Episode 16: Blueprint, a conversation with Robert Plomin

Filed under: Behavior Genetics,blueprint,Genetics — Razib Khan @ 4:54 pm

The Insight Show Notes — Season 2, Episode 16: Blueprint, a conversation with Robert Plomin

Correlation on a scatterplot

This week on The Insight (Apple Podcasts, Stitcher and Google Podcasts) we discuss behavior genetics with Robert Plomin, one of the eminent researchers in the field.

Much of the discussion was around Plomin’s new book, Blueprint: How DNA makes us who we are. He admitted that many people were not happy with the book. Nature, in particular, published a rather negative review. But in general, Plomin was happy about the reviews (e.g., a relatively positive review was published in National Review by the author of this post!).

There was some discussion about the history of behavior genetics, the study of individual differences, and the origins of differential psychology with Francis Galton.

We also discussed the “blue period” of the field when Plomin was studying psychology in the 1970s when most researchers were not interested in heredity.

Rather, Behaviorism was in vogue in academia, and Freudianism in the general public.

Moving into the 21st century, we discussed polygenic risk scores, which synthesize genomic technology with behavioral genetic statistics, and Plomin’s enthusiasm for them as tools for discernment. In particular, he discusses his own background as someone from a working-class family where he was the only one to go to college.

We also discussed the difference between heritability, shared environment (family), and non-shared environment, and why genetics is the signal we can understand. In this context, we brought up the late Judith Rich Harris, who emphasized how much we talk about the shared environment, even though it seems rather marginal for many characteristics.


The Insight Show Notes — Season 2, Episode 16: Blueprint, a conversation with Robert Plomin was originally published in Insitome on Medium, where people are continuing the conversation by highlighting and responding to this story.

A toxic cocktail of American narcissism and Indian American self-righteousness

Filed under: Culture — Razib Khan @ 10:44 am

Like many of you, I’m monitoring what’s going on in the Indian subcontinent. I’m not saying much because I don’t know much. No value to add.

But then this showed up in my timeline, and I honestly could not believe that even the confluence of characteristics we’ve been talking about recently might lead to such bizarre self-obsessed comments:

I see this person’s comments in my timeline way too often. Best case scenario is that she’s some sort of ideological grifter who knows how to push buttons. But this indecent.

The age of prenatal genetic screening is here (let’s call it that!)

Filed under: Genomic prediction,Personal genomics,PGD — Razib Khan @ 10:00 am

In the spring of 2010, I went to the studios of KQED in San Francisco to record an interview with a radio show on the BBC about PGD. Preimplantation genetic diagnosis. I haven’t thought much about the issue in the near ten years since then. Which in a personal sense certainly reflects my luck and circumstance.

But I’m thinking about the issue after reading this story from Emily Mullin, We’re Already Designing Babies: Expanded genetic testing of embryos represents a new era of family planning. But how far should the technology go?:

JJill Pinarowicz’s life has been shaped by a mutation in her mother’s DNA. The genetic error gave her two brothers a rare disease called Wiskott-Aldrich syndrome….

Both of Pinarowicz’s brothers passed away from complications of the disease. One died as a toddler, before she was born, and her other brother died at age 18, when Pinarowicz was a teenager.

Pinarowicz thought it would be too risky to have her own children….

The technique is called preimplantation genetic testing (PGT). By using PGT together with in-vitro fertilization, Pinarowicz and her husband had a healthy son in May 2017.

An incredible “feel-good” outcome so far. And not surprising. I have become more conservative about technology since I first started writing on the internet in the early 2000s, but I will never oppose these sorts of genetic technologies that allow couples whose offspring are at high risk of developing serious debilitating conditions to avoid these scenarios. But the magnitude of how common this now took me aback:

The U.S. Centers for Disease Control and Prevention (CDC) reported in January that PGT was used in 22 percent of IVF cases in 2016, up from just 5 percent in the previous year.

Since the last statistic Mullin could find was from 2016, it’s almost certain that the proportion is greater than 22 percent today. The numbers for 2018 seem difficult to find, but it seems likely that ~75,000 live-births per year in the USA are now due to IVF. Worldwide there are in the range of 10 million humans alive today due to IVF.

How relevant IVF is to fertility varies by social and demographic variables. I know a fair number of people who have done IVF. The average age of a mother at her first birth is 32 in San Francisco and 31 in Manhattan. As many of you probably know many options relating to fertility and genetic testing come “online” for American insurance companies at age 35.

When you transform blue-sky exotic basic science into mass technology they become far less controversial. One of the major themes of Carl Zimmer’s new book, She Has Her Mother’s Laugh, was the vocal and mainstream nature of 20th-century eugenics. A major criticism of Robert Plomin’s Blueprint is that it was resurrecting genetic determinism. Let me quote Mullin:

In Iceland, for instance, the widespread availability of prenatal genetic testing has meant that nearly 100 percent of women choose to abort a fetus with Down syndrome, which has led to a near eradication of babies being born with the condition.

What is in a word? Something in the future is worrisome. Something that professional dual-income-no-kids couples do in their attempt to attain the classic bourgeois lifestyle is not so worthy of comment? Outside of the pro-life movement the discussion of the ubiquity of screening for Down syndrome seems rather muted, even though it is widespread. While we may furrow our brows over decisions made based on polygenic risk scores, the reality is that the age of Mendelian screening is here. It is not speculative science, but applied medicine.

Call it what you want to call it.

The age of prenatal genetic screening is here (let’s call it that!)

Filed under: Genomic prediction,Personal genomics,PGD — Razib Khan @ 10:00 am

In the spring of 2010, I went to the studios of KQED in San Francisco to record an interview with a radio show on the BBC about PGD. Preimplantation genetic diagnosis. I haven’t thought much about the issue in the near ten years since then. Which in a personal sense certainly reflects my luck and circumstance.

But I’m thinking about the issue after reading this story from Emily Mullin, We’re Already Designing Babies: Expanded genetic testing of embryos represents a new era of family planning. But how far should the technology go?:

JJill Pinarowicz’s life has been shaped by a mutation in her mother’s DNA. The genetic error gave her two brothers a rare disease called Wiskott-Aldrich syndrome….

Both of Pinarowicz’s brothers passed away from complications of the disease. One died as a toddler, before she was born, and her other brother died at age 18, when Pinarowicz was a teenager.

Pinarowicz thought it would be too risky to have her own children….

The technique is called preimplantation genetic testing (PGT). By using PGT together with in-vitro fertilization, Pinarowicz and her husband had a healthy son in May 2017.

An incredible “feel-good” outcome so far. And not surprising. I have become more conservative about technology since I first started writing on the internet in the early 2000s, but I will never oppose these sorts of genetic technologies that allow couples whose offspring are at high risk of developing serious debilitating conditions to avoid these scenarios. But the magnitude of how common this now took me aback:

The U.S. Centers for Disease Control and Prevention (CDC) reported in January that PGT was used in 22 percent of IVF cases in 2016, up from just 5 percent in the previous year.

Since the last statistic Mullin could find was from 2016, it’s almost certain that the proportion is greater than 22 percent today. The numbers for 2018 seem difficult to find, but it seems likely that ~75,000 live-births per year in the USA are now due to IVF. Worldwide there are in the range of 10 million humans alive today due to IVF.

How relevant IVF is to fertility varies by social and demographic variables. I know a fair number of people who have done IVF. The average age of a mother at her first birth is 32 in San Francisco and 31 in Manhattan. As many of you probably know many options relating to fertility and genetic testing come “online” for American insurance companies at age 35.

When you transform blue-sky exotic basic science into mass technology they become far less controversial. One of the major themes of Carl Zimmer’s new book, She Has Her Mother’s Laugh, was the vocal and mainstream nature of 20th-century eugenics. A major criticism of Robert Plomin’s Blueprint is that it was resurrecting genetic determinism. Let me quote Mullin:

In Iceland, for instance, the widespread availability of prenatal genetic testing has meant that nearly 100 percent of women choose to abort a fetus with Down syndrome, which has led to a near eradication of babies being born with the condition.

What is in a word? Something in the future is worrisome. Something that professional dual-income-no-kids couples do in their attempt to attain the classic bourgeois lifestyle is not so worthy of comment? Outside of the pro-life movement the discussion of the ubiquity of screening for Down syndrome seems rather muted, even though it is widespread. While we may furrow our brows over decisions made based on polygenic risk scores, the reality is that the age of Mendelian screening is here. It is not speculative science, but applied medicine.

Call it what you want to call it.

BrownCast Podcast episode 17: India-Pakistan conflict, Hindu nationalism, Cosmopolitanism

Filed under: Podcast — Razib Khan @ 1:04 am

Another BP Podcast is up. You can listen on LibsyniTunes and Stitcher. Probably the easiest way to keep up the podcast since we don’t have a regular schedule is to subscribe at one of the links above. You can also support the podcast as a patron (the primary benefit now is that you get the podcasts considerably earlier than everyone else…). Would appreciate more positive reviews.

My next planned podcasts were going to be next week…but then world-events intervened. We recorded this before the latest developments in the border clashes between India and Pakistan. We spend probably 35% of the conversation on that topic. But…in a wide-ranging discussion we discuss knitting & racism, Hindu nationalism, Maratha(i)(?) nationalism, and the future of India, with a cosmopolitan <<<Third Culture>>> Indo-British-American professional.

The conversation between our guest, Amey, myself, and Omar, was spirited. I actually had to edit out sections where we kept interrupting each other to get in a word in edgewise! That being said, there is one section where I drop into an American colloquialism which is atypical for me, and I state I’ll “edit it out.” But I left it in since to some extent I did play the role of the befuddled and fearful American from the heartland who just wants the world safe for freedom and consumerism!

February 26, 2019

A blueprint in our genes for behavior?

Filed under: Eugenics,Genetics,Personality,Psychology — Razib Khan @ 4:44 pm

Since the emergence of the field of genetics over a century ago the question of “nature vs. nurture” has loomed large over the field when it comes to the nature of “human nature.” The very term “human nature” is a tell as to its origins and early connotations: the early idea was that we are “born that way.” Society was seen to have a hereditary basis, as was your own individual life outcome.

It is true that in the early decades of genetics, researchers were preoccupied with fruit flies, pedigrees, and equations. But genetics was not alone on the scene. Eugenics, a social and cultural movement which presented itself as an application of hereditary science to improve the human race, developed in the same decades to great public aclaim. One of the founders of the field of statistical genetics, Francis Galton, was also the founder of eugenics!

Though the history books tell us about the history of eugenics with the shocking culmination of the horrors Nazi Germany, the fact is that the nation which arguably took up eugenics most enthusiastically in the decades before World War II was the United States of America! This was a period when socialists such as H. G. Wells, and conservatives such as Winston Churchill, both supported eugenics. The German Nazis modeled many of their policies and laws on American precedents.

It is in the context of this history that the branch of psychology dealing in heritable individual differences, behavior genetics, slipped into the shadows in the decades after the defeat of the Nazis. The nature of heritability of behavioral characteristics was somewhat taboo because they had been the subject of fascination by eugenicists. Genetics generally restricted itself to healing terrible diseases. When it comes to other aspects of mind and body it receded. For example, Freudianism and Behaviorism were more common perspectives brought to bear on individual differences and outcomes in psychology. Though these perspectives did not reject biological inheritance as such, they focused on environmental inputs and outputs.

Schizophrenia was seen as a disease of upbringing or environmental exposure. Not one of genetic transmission from parent to offspring (today we know that schizophrenia is 80% heritable!).

This situation began to change with the emergence of a field of cognitive science which held that some aspects of psychology were innate, such Noam Chomsky’s theory of universal grammar, which implied a biological underpinning for our facility with language. And, just as some psychologists were exploring the inherited bases of our universal behaviors and aptitudes, others began to look more closely at differences. Human variation.

The reemergence of behavior genetics, the study of individual differences, and the attempt to infer both the environmental and genetic components of various outcomes evolved in the context of large longitudinal studies of twins and their siblings. The logic here is simple: the correlation in a characteristic such as height between identical twins is nearly perfect. For siblings (and fraternal twins), there is a correlation, but it is far weaker because sibling relatedness is only 50%. If the correlation on a behavioral trait, such as the likelihood of schizophrenia, is correspondingly greater between identical twins than between their siblings, then it is highly heritable. Genes play a large role in the trait’s expression. In contrast, if there is no difference between twins and how siblings correlate on a trait, then that suggests that there is not much of a genetic basis to the characteristic. Recall, identical twins by definition are more genetically related than two siblings.

There are of course many theoretical objections to twin studies (e.g., perhaps parents treat twins more similarly than they do siblings), and the statistical abstruseness of behavior genetics means that its implications and findings did not get broad coverage as the field matured in the late 20th century. Despite several decades of research, by the year 2000, it is likely most people were not aware of the substantial heritability of many behavioral and psychological characteristics, from personality disposition to mental illness.

The last few decades have changed this, in part because the new science of genomics, which looks beyond statistical correlations of characteristics to raw DNA sequence, has begun to merge with behavior genetics. Because psychological characteristics were almost always defined by the small effect of many numerous genes classical genetics did not have the power to locate any genes that were involved in psychological variation. But with massive sample sizes of as much as a million and hundreds of thousands of genetic positions, new research is now confirming the statistical work from twin studies that many psychological characteristics are substantially heritable.

Illumina Sequencer

The study of human nature and our differences and the possible genetic causes of them began with a tragedy and a travesty. Eugenics marred the legacy of many early geneticists, and its application in the United States and Nazi Germany were crimes against humanity. But as the 21st century proceeds the study of human psychology and its genetic basis is now becoming a true science. Able to describe, as well as predict.

But, it turns out its powers of prediction are quite modest, far less than any eugenicist would have foreseen or dreamt of. The truth is a genetic test can give you only a small improvement on your odds of knowing the likely track of your life. And perhaps that is for the best.


A blueprint in our genes for behavior? was originally published in Insitome on Medium, where people are continuing the conversation by highlighting and responding to this story.

I now support quotas on (South) Asian Americans at elite universities

Filed under: America,Culture — Razib Khan @ 4:36 pm

A Harvard Law Professor Is Representing Harvey Weinstein. Students Say This Makes Them Unsafe, Demand His Resignation:

Harvard’s administration is taking students’ concerns seriously, and has agreed to conduct a review of Sullivan.

“In this situation, we would like to have a more complete understanding of the current environment at Winthrop House,” wrote Dean of the College Rakesh Khurana in an email, according to The Harvard Crimson.

One of The Crimson’s own staff members*, Danukshi Mudannayake, is spearheading the effort to remove Sullivan. She started a change.org petition that claims his representation of Weinstein as “not only upsetting, but deeply trauma-inducing.” According to Mudannayake, Sullivan has made clear that he does not “value the safety of students he lives with in Winthrop House.”

The American system is upsetting. To be frank, it’s a feature, not a bug. Presumption of innocence exists not in cases where it is easy to support the innocent, but in cases where it is hard. In the United States of America there are people who commit horrible crimes, and lawyers who defend them and lawyers who prosecute them. This is all part of the system.

It is tough on the heart. But it works. Unlike some societies, the will of the majority does not dictate the outcome (in theory).

Seeing those names was like a punch in the stomach. This is not the sort of “model minority” that I’d like to encourage.

Open Thread – Brown Pundits

Filed under: Open Thread — Razib Khan @ 11:29 am

Please keep the other posts on topic. Use this for talking about whatever you want to talk about.

February 25, 2019

The airstrikes

Filed under: Geopolitics — Razib Khan @ 11:46 pm

Indian Jets Strike on Pakistani Side of Kashmir Line:

Indian warplanes conducted airstrikes in the Pakistan-controlled side of Kashmir on Tuesday, Pakistani officials said, in an escalation of tensions between the nuclear-armed nations after a suicide bombing against Indian troops in the disputed region this month.

If confirmed, it would be the first time that Indian aircraft had crossed the Kashmir Line of Control to strike in years. But it was unclear what, if anything, the attack jets hit on the Pakistani side, raising the possibility that India was making a calculated bet to assuage public anger but minimize the risk of a major Pakistani military response.

Curious about value-add thoughts….

Do people in India care about ‘racist’ knitters?

Filed under: Culture — Razib Khan @ 6:30 pm


There is a weird controversy about a white knitter who was perceived to be racist against Indians because they were worried about going to India because it was so alien from her experience? At least that’s what I get from the conversation. See the above exchange for some more context.

The mainstream website Vox, published something relating to this, The knitting community is reckoning with racism. The post shows that this is really about Americans more than about Indians. For example:

As someone who is mixed-race Indian, to me, her post (though seemingly well-meaning) was like bingo for every conversation a white person has ever had with me about their “fascination” with my dad’s home country; it was just so colorful and complex and inspiring. It’s not that they were wrong, per se, just that the tone felt like they thought India only existed to be all those things for them.

The author of the piece is a mixed-race American. Her mother is Irish American, and her father an immigrant from India.

My question is simple: what do people in India think about this?

February 24, 2019

Open Thread, 02/24/2019

Filed under: Open Thread — Razib Khan @ 11:12 pm


Probably don’t watch this if you are hungry. It’s on Netflix.

The latest episode of The Insight featured a very long discussion with Jeffrey Rose. If you are curious about the relationship of southern Arabia to the cultures of northeast Africa during the Middle Paleolithic, check it out!

The Freemasons. Not the deepest book. But interesting.

The Linked Selection Signature of Rapid Adaptation in Temporal Genomic Data.

Accurate inference of tree topologies from multiple sequence alignments using deep learning.

Human genetic disease is greatly influenced by the underlying fragility of evolutionarily ancient genes.

Unbiased estimation of linkage disequilibrium from unphased data.

China’s CRISPR twins might have had their brains inadvertently enhanced. The title is just plain wrong. Unfortunately the piece “traveled” and now I’m seeing it cited at places like National Review, Eugenics-Engineered Babies’ Brains Changed by CRISPR.

Supreme Court Delivers Unanimous Victory for Asset Forfeiture Challenge.

World’s largest bee, once presumed extinct, filmed alive in the wild.

David Slone Wilson has a book out, This View of Life: Completing the Darwinian Revolution.

‘Austerity, That’s What I Know’: The Making of a U.K. Millennial Socialist.

Ancient whole genome duplications and the evolution of the gene duplication and loss rate.

Recombination and mutational robustness in neutral fitness landscapes.

We Must Defend Free Thought. This is really about Scott Alexander, who is becoming too influential for the tastes of some.

Reihan Salam new President of Manhattan Institute.

Viruses rule over adaptation in conserved human proteins.

A more complex tree of recent human origins

Filed under: Human Evolution — Razib Khan @ 7:11 pm


Sometimes charts are useful. The above plot does not have branch lengths which are proportional to length. But, they capture I think the rough topology. I’ve also put notes on there.

Some of the branches are certainly wrong. We’ll know more in the next few years.

Ancestral proto-Eurasians may have had wavy hair

Filed under: Anthroplogy,anthropology — Razib Khan @ 1:31 am

Australian Aboriginal child photographed in the late 1850s

The above chart is from The Simons Genome Diversity Project: 300 genomes from 142 diverse populations. The basic outlines of this tree were evident as far back as L. L. Cavalli-Sforza. But there were always small details that caused issues. In particular, were East Asians a more natural clade with Australasians or with Europeans? Today with both ancient DNA and whole-genome analyses two things are clear which might have been confounding earlier analyses:

  1. There has been gene flow between many East Asian and European populations. If you look closely at the ancient DNA work it is clear that East Asian gene flow is present in Mesolithic hunter-gatherers. Conversely, many northern Chinese have show low levels of West Eurasian ancestry (I suspect mediated through Mongols and Turks).
  2. The peoples of Australasia have Denisovan ancestry, which is distinct from anything found in East Asians and Europeans (small trace proportions of Denisovan in the former notwithstanding).

With these considerations accounted for, it seems clearer that the peoples of Oceania and East Asia descend from a common group that pushed from the west. And, the most ancient substratum in South Asia is also part of this broad family of peoples, who diversified in the period between 45 to 55 thousand years before the present. This is in contrast to the peoples to the west, who gave rise to Ice Age Europeans, Middle Easterners, and more distantly the “Ancient North Eurasians” who seem to be the first settlers of Siberia.

To understand the context for the emergence of characteristics and traits one has to understand the demographic histories and relationships between people. We are coming close to establishing the latter with good certainty for most groups. Though the sea levels separated New Guinea from Australia only within the last ~10,000 years, genetic work suggests that the differentiation between highland Papuans and Australian Aboriginals long predates this. If I had to hazard a guess I’d suggest that the huge ecological differences were probably critical in reducing gene flow between the wet and warm highlands of Sahul, and the broad deserts that occupied what became Australia.

 

Andamanese child

With that, I want to talk about hair form. Early physical anthropologists grasped onto this characteristic because it is so easy to define and measure. Hair can be straight, wavy, curly, and tightly curly (“woolly”). Even within tightly curled hair, there is variation. The San Bushmen have “peppercorn hair,” which means its curl is tighter than that of their Bantu neighbors.

One assumption that many people make is that originally anatomically modern humans had tightly curly hair, rather like modern Africans. Additionally, the depictions of Neanderthals I’ve seen do not give them this form of hair. Though there are mutations that change hair form (no surprise they are shared with dogs and cats), looking at the minimal literature on this trait it seems that curliness is somewhat polygenic. It doesn’t segregate like a Mendelian trait.

Likely one reason that curly hair is presumed to be ancestral is that many of the Australo-Melanesian peoples exhibit similar hair form to Africans, and these people have long been thought to be more “ancient.” But this is a fallacy. The ancestors of the Andamanese and Negritos of Southeast Asia are no more ancient than those of the Han Chinese. All descend from the same group of people who pushed eastward around 50,000 years ago.

Until recently I had assumed that the best model for the indigenous people of South Asia, the “Ancient Ancestral South Indians” (AASI), were the Andamanese. And yet one group in south India, the Paniya, are ~75% AASI in their ancestry. Looking through photographs of this tribe with a keen eye toward hair form, though their hair is curly, on the whole, no individuals show extremely tight curls.

And of course, Australian Aboriginals famously, on the whole, do not have tightly curled hair. Most of them are wavy haired (though curlier hair form is more common on the northern coast).

Where does this leave us? Of non-African descendent populations, there are a diverse set of lineages. None of the people of West Eurasia have tightly curled hair. Of those to the east, only the Negritos of South and Southeast Asia, and the people of Melanesia do so. But the Australian Aboriginals, who are closer to Melanesians than any other population, do not have tightly curled hair (though the Tasmanians, who separated from the Aboriginals ~10,000, may have had so based on the photographs). The peoples of Northeast Asia and the Americas, do not have tightly curled hair, obviously.

The primary confound here is selection. Hair form is a polygenic trait. It is not unreasonable to think that the humans moving out of Africa would carry standing variation, and that selection for curlier hair in some tropical climates would result in convergent evolution. The ancestors of Papuans and Negritos then may have had wavy hair, and Australian Aboriginals simply maintained this.

Ultimately doing the same thing with hair that was done with pigmentation will probably answer the questions of ancestral-derived states.

February 23, 2019

“Out of Africa” in 2019

Filed under: Historical Population Genetics,Out-of-Africa,PremiumPost — Razib Khan @ 9:32 pm

The figure to the left is from Paleolithic DNA from the Caucasus reveals core of West Eurasian ancestry. It is a graph which captures general features of human population historical relationships as we understand them today. Or at least the model fits the data (remember, many models may fit the data!). The graph is complex…but even within the text of the preprint, the author admits that it is characterized by simplifying assumptions, which nevertheless are informative of some general dynamics and processes (e.g., pulse admixtures).

To some extent, the whole last generation or so has been characterized by the victory of a simplifying assumption that captures general truths about the past, with the accumulation of modifications on the margins as more nuanced results enter the picture. The simplifying assumption I am talking about here is the “out of Africa” 50,000 years ago with a total replacement of all other human lineages framework.

By the last quarter of the 20th century, a combination of archaeological and genetic evidence pointed to the likelihood of a massive bottleneck and expansion of humans outside of Africa in the relatively recent past. In the pre-genomic era, the tools were coarse, from uniparental lineages, classical markers, microsatellites, morphometric analyses, as well as archaeological surveys. But, they strongly pointed to massive expansion and population turnover ~50,000 years ago. This, combined with a line of thinking which suggested that Neanderthals were “evolutionary dead-ends” led to the thesis that there was a total replacement.

To a great extent, this model seems to hold up in the broad sketch. But not to an absolute and total degree. Some paleoanthropologists and geneticists were pointing out for decades that the tools we had could not exclude the possibility of admixture at lower fractions with earlier lineages in Eurasia on purely statistical grounds. These scholars were correct, as it turns out. There is now high confidence that in the range of 1-5% of the ancestry of non-Africans derives from highly diverged “archaic” lineages, Neanderthals and Denisovans. The fraction is low enough that more coarse methods did not definitively pick them up, and without ancient genomes, the “game of inference” was not dispositive in either direction. This, despite the fact that these Eurasian hominins’ ancestors seem to have diverged from those of modern humans ~750,000 years ago. Ultimately, scientists needed a physical ancient genome which they could compare to modern populations to come to this conclusion (before the Denisovan result, scientists had been noticing anomalies in Oceanian data for a decade or so but generally ignored it as beneath comment…a presentation was given an anthropology conference on archaic admixture in Oceania right before the Denisova cave paper).

The second major issue is that the massive expansion and bottleneck that occurred ~50,000 years ago may not explain all of the remaining ancestry that is not “archaic.” That is, there were many modern human lineages present 50,000 years ago. The major lacunae in the current model is a huge one: populations within Sub-Saharan Africa maintained larger population sizes throughout this event. And, anatomically modern humans predate this expansion by hundreds of thousands of years. From an archaeological perspective, a lower limit is 200,000 years ago, and an upper limit probably exceeds 300,000 years ago. Additionally, there are “deep lineages” within Africa which clearly predate the expansion 50,000 years ago. There is a strong consensus that the Khoisan people have at least some substantial ancestry that diverged more than 150,000 years ago from other humans, and tentative suggestions from several different research groups suggest that there are even more “basal” (deep divergence) lineages in parts of West Africa that the component within the Khoisan.

This does not even address the likelihood that some “archaic” ancestry persists within Sub-Saharan Africa just as it does outside of Sub-Saharan Africa.

The third issue are diverged anatomically modern humans in eastern Eurasia. By this, I mean lineages which are in a clade with anatomically modern humans rather than Neanderthals and Denisovans, but, split off from other non-Africans before the massive expansion of ~50,000 years before the present. There are two major points here. First, the circumstantial evidence that these people existed is very strong now. We know this from archaeological sites in Southeast Asia and possibly China. And, there is genomic evidence that a lineage closer to modern humans contributed ancestry to Altai Neanderthals ~100,000 years ago. Second, there is some suggestive, though highly disputed, evidence of low levels of earlier-than-50,000-years-ago modern human ancestry in Papuans. The fractions are low, just as they are with Neanderthals. A major problem with detecting diverged lineages at low fractions without ancient DNA is that the statistical power is not there to be definitive. These people are far closer to the dominant “50K expansion” group than Neanderthals and Denisovans.

Remember, without ancient genomes, many geneticists would probably be skeptical to this day about Neanderthal admixture, though there had been suggestions from the genome-wide data of archaic admixture by the middle years of the 2000s. The Neanderthal genome obviously changed our priors, but without ancient genomes, we don’t have as much ability to differentiate possible models which fit the data we have in a manner which resolves disagreements from what I can tell when we are talking about low levels of admixture.

Finally, backing up to the figure at the top of this post: notice that there is now a model with two nestings of “basal” populations in relation to the major non-African ancestry component that expanded ~50,000 years ago. That is, there are famous “Basal Eurasians”, but Lazaridis et al. are proposing a “Basal North African” clade, which diverged from Basal Eurasians & the major Eurasian components before the latter two split apart. Lazaridis et al. also propose ~10 percent of Yoruba ancestry is from the Basal North African clade. There has been a lot of talk for years that Yoruba was an unfortunate choice for “unmixed Sub-Saharan African”, because there are clearly some Neanderthal alleles in this population, indicative of some “back-migration.” But in fact, from modern populations, it would probably be impossible to pick an “unmixed Sub-Saharan African” because there aren’t any.

As I make clear in my previous post, there is a fair amount of evidence that modern Sub-Saharan Africans have been impacted by gene flow from outside of Sub-Saharan Africa. Or at least a population which is somehow closely connected to the ancestors of non-Africans. A substantial proportion of this is probably due to the major modern human expansion that dates to 50,000 years ago. But, some if it probably predates this period, and, some of it postdates this period. If Lazaridis et al. are correct that there is Basal North African admixture in West Africa, then it may actually predate the migration 50,000 years ago because this lineage separated in the period between 50 and 100,000 years ago (of course the admixture could have been later) from other North African-West Asians. And, we happen to know of at least once Holocene era migration into this region of Africa that was prehistoric.

Circa 2010 we had a simple story. The Omo find in Ethiopia was the earliest anatomically modern human, dated to 200,000 years ago. Around 50,000 years ago anatomically modern humans left East Africa and replaced everyone else, in Africa, and outside of Africa. Recent human evolution proceeded from Africa, to the Near East, and then outward in all directions.

I believe this story is not fundamentally flawed in a broad sense. If we ever discover ancient DNA that dates to before 50,000 years ago in East Africa, I think we will find that most modern East Africans share substantial, perhaps even preponderant, ancestry from the expansion that dates to 50,000 years ago. But, the high diversity of extant Sub-Saharan Africans and the suggestions of deeply basal lineages through statistical inference indicate that “deep structure” of modern humans within Africa was not erased by migration from the north or east, but that the combination of the two led to the emergence of African lineages as part of the dynamic process of admixture ~50,000 years ago.

If Basal Eurasians and Basal North Africans, are discovered, they too are part of the story of “deep structure.” And, the earlier modern lineages that were present in eastern Eurasia may also be part of the “deep structure,” though population turnover may also have erased that imprint by the present.

Twenty years ago many scholars conceived of a model where a very small founding population in East Africa expanded and replaced all other humans in “blitzkrieg” fashion. There was massive radiation into Eurasia and Oceania ~50,000 years ago from a small ancestral population, while sister modern lineages in Africa were also replaced. This is still evident in indications of a massive bottleneck, and shared Neanderthal ancestry, in groups from Northwest Eurasia to the New World to Australia. But, there was also a lot of older “deep structure” that was absorbed and integrated. Some of this is easy to pick up because it was so different. Neanderthals. Denisovans. But some of them, like the Basal Eurasians and Basal North Africans, were likely part of the broad family of modern human lineages that were developing in concert for hundreds of thousands of years, a great fanlike phylogenetic tree descended from common ancestors. Further south in Africa there were probably other modern groups, whose phylogenetic relatedness would be a function of their distance to the proto-North African-West Asians. Out of the broad radiation of “modern humans” one group contributed disproportionately to the ancestry of most humans today. More in East Asia than in Europe, and more in Europe than in the Near East, and more in the Near East than Africa.

As we are in a stage of greater complexification errors and mistakes will be made. The evaluation of the models are only as good as the data we have. More data will come.

Addendum: I have not specified where the dominant modern signal is coming from. I think the candidates are probably the Levant, Arabia, all of Northern Africa, and Eastern Africa. Without far more ancient DNA in these regions we may never know.

February 21, 2019

Reevaluating “multiple origins” for modern humans

Filed under: Human Evolution — Razib Khan @ 3:28 pm

Following up on the post below, The Deep Origins Of East African Hunter-Gatherers, as well as some discussions on Twitter, I think I want to do some clarification about where I think we are now. My thoughts shouldn’t be a surprise if you have read everything I’ve said, but I may not have put them all together in one place.

Around the turn of the century, nearly twenty years ago, the consensus had definitively turned against a “multiregional” origin of modern humans, toward one where an “out of Africa” migration ~50,000 years ago was paramount. Many people took the “paramount” part and simply asserted that we are all Africans descended from a population that flourished in the east of the continent about 50,000 years ago. There was a lot of circumstantial evidence to support this, at least spottily, from both archaeology and genetics. There were also problems and lacunae in both fields. But the data was spotty enough that the extreme position was defensible.

We now have a lot more information and need to update our model. First, most people agree that indigenous Eurasian hominins, Neanderthals and Denisovans, contributed to the ancestry of people outside of Sub-Saharan Africa. Additionally, it’s been evident for a long time now that the massive population bottleneck that is present in all non-African populations dating to ~50,000 years ago is far less evident in Sub-Saharan African genomes.

Finally, it’s pretty clear that humans with modern morphology were present within Africa for hundreds of thousands of years before the movement out of Africa.

Therefore, a new reevaluation of the old model that is converging is a possibility is that multi-regionalism was operative within Africa for hundreds of thousands of years, followed by a massive expansion on the northeast edge of Africa that resulted in most of the ancestry of other human groups outside of the continent, with some assimilation (e.g., Neanderthal). This is a far more complicated model than the older one, but sometimes the truth is more complicated than simplicity.

But I think we’ll probably need to make further modifications, and that’s because gene flow is not always unidirectional. Specifically, the Y chromosomal work, in particular, is strongly indicative of migration of lineages more typical of Eurasians expanding within Africa within the last 50,000 years. And, as a commenter on this weblog has pointed out, even the “deep lineages” within Africa, Y haplogroups A and B, show signs of massive expansion within the last 50,000 years.

This may mean that a population liminal to Africa and Southwest Asia underwent a very rapid expansion ~50,000 years ago. The replacement of indigenous lineages was far more thorough outside of Africa, with 5% or less assimilation in most places. But, it probably impacted Africa as well. Though a larger fraction of diverged modern ancestry persisted in Africans than Eurasian hominin ancestry in non-Africans. In other words, the high genetic diversity of Africans today, and particular groups like the Khoisan, is due to the mixture between an ancient migration from the same population that was the source of “out of Africa” in Eurasia and Oceania, and disparate deeply structured lineages within Africa, that date back 200-400 thousand years ago.

Additionally, I think some earlier “modern” lineages were assimilated in eastern Asia with the latest migration out of Africa. And, some of the ancestry within Africa probably predates the origin of anatomically modern humans, analogous to the case of Neanderthals and Denisovans.

Note: This is not that different of a model from Dienekes Pontikos’ ideas in the 2000s, More support for the Afrasian/Palaeoafrican hypothesis, at the high level. Basically the more evidence has come in, the less crazy his model has gotten.

February 20, 2019

The Insight Show Notes — Season 2, Episode 15: The Prehistory of the Arabian Peninsula

Filed under: Archaeology,oman,Out-of-Africa — Razib Khan @ 3:56 pm

The Insight Show Notes — Season 2, Episode 15: The Prehistory of the Arabian Peninsula

Dhofar, Oman, during the “wet season”

This week on The Insight (Apple Podcasts, Stitcher and Google Podcasts)we discuss the prehistory of the Arabian peninsula with archaeologist Dr. Jeffrey Rose. We range over tool technology, geology, and the relationship between language and genetics.

Watch him in action as he instructs students on how to identify stone tool-making techniques:

As Rose does much of his fieldwork on the Dhofar uplands of southern Oman, we reviewed the unique geography and history of this region. Located on the border with Yemen, Dhofar is subject to the monsoons and experiences a rainy season. Unlike the deserts to the north and the interior, this region of Oman shares more biogeographically within the African savannas than the temperate zones. Rose mentions that even organisms such as frogs and snails exhibit differences between Dhofar and the rest of Oman.

There was extensive discussion about the Nubian Complex of Dhofar. This is an archaeological culture which dates to the Middle Paleolithic and ties Africa to Arabia. This is important because it may help us trace the “Out of Africa” migration and concretely connects Africa to Arabia. In keeping with Dhofar’s uniqueness in the region, the Nubian Complex extends no further to the north and east. An outpost of Africa if you will.

We mentioned the “Green Arabia” theory, which posits that there were past periods when the aridity of the region was far less than what it is today.

Rose also discussed in detail the Levallois technique, a variant of which helps define the Nubian technology that is so distinctive and easy to trace.

There was a review of the ethnographic diversity of southern Arabia. In particular, the indigenous people of Dhofar, the Mehri, as well as various other “South Semitic” ethno-linguistic groups. Rose reminds us that Arabic was not traditionally the native language from Yemen to Oman, but rather was a recent introduction in historical times.

The closest languages to South Arabian dialects are to be across the Red Sea, in the highlands of Ethiopia. This highlights the fact that Rose’s work traces migrations out of Africa, but may also help flesh out migrations back into Africa.

We discussed the origins of the Sumerians in the Gulf region when the sea levels were much lower. Rose also alluded to the fact that Arab legends suggest that the people of southern Arabia were originally a very different group of agro-pastoralists.

Finally, Rose points to the genetic work of David Reich’s lab, and how their Middle Eastern work aligns with his own findings. We discuss “Basal Eurasians” and how they might relate to Arabian prehistory.

More videos of Dr. Jeffrey Rose:


The Insight Show Notes — Season 2, Episode 15: The Prehistory of the Arabian Peninsula was originally published in Insitome on Medium, where people are continuing the conversation by highlighting and responding to this story.

Indians in Kerala are less religiously polarized, those in Bihar are more polarized

Filed under: World Values Survey — Razib Khan @ 2:27 pm


Because some commenters on this weblog have a lot more lived experience within India than I do, you try to bullshit me. I suspect it, but I can’t prove it.

But I realized today that World Values Survey is broken down by region within countries. This means I can at least doublecheck some of the crazy assertions some of you make.

What I did is pretty simple: I selected India as the country and then selected regions as the first variable. I crossed it with a question about how much people trust those of other religions.

One thing that jumps out of the result is that trust across religions is highest in Kerala. There isn’t a huge difference across the north, but it seems lowest in Bihar. This makes sense.

These sorts of single results need to be treated with caution. The main issue is that respondents are usually asked in their native language, but word choice can bias the outcome.

I invite readers who are interested in bullshitting less to look at the WVS themselves. Raw table below the fold (with N’s).

State N Trust completely Trust somewhat Do not trust very much Do not trust at all
Andhra Pradesh 305 11.5 50.2 34.1 4.3
Bihar 330 4.5 24.5 43.6 27.3
Chhatisgarh 98 4.1 54.1 36.7 5.1
Delhi 69 13 30.4 39.1 17.4
Gujarat 248 8.5 39.9 31 20.6
Haryana 122 29.5 32.8 19.7 18
Jharkhand 154 3.9 48.1 44.2 3.9
Karnataka 229 10.5 48.5 31.9 9.2
Kerala 184 48.9 37.5 12.5 1.1
Madhya Pradesh 239 13.4 45.2 25.1 16.3
Maharashtra 236 20.8 42.8 18.2 18.2
Orrisa 319 0.6 39.2 45.1 15
Punjab 146 11 44.5 34.9 9.6
Rajasthan 275 13.1 32.4 31.6 22.9
Uttar Pradesh 555 21.4 31.5 26.3 20.7
West Bengal 286 15 39.9 32.5 12.6
Uttarakhand 62 4.8 33.9 45.2 16.1

Brown is all, all is brown

Filed under: Culture — Razib Khan @ 12:57 am

There emerged a question in the comments below as to what was “brown” or “desi”?

Ah, the old demarcation problem! Since there is no “Pope of Brownness” we can all offer our opinions. I take a “liberal” and “broad” view.

There are children adopted from India in the United States who are as physically South Asian as anyone. But often they were raised as English-speaking American Christians. Though many attempt to reconnect with “their culture”, the reality is that their family is the family who adopted them. Their culture is the culture in which they grew into adulthood. But, because of the way they look people make assumptions about them. Perhaps people are racist against them as South Asians.

Despite their involuntary cultural alienation from all things South Asian, I have a difficult time thinking that these kids are not brown. Especially if they so want to identify as such.

In contrast, you have the case of people of various races who convert to religions with a South Asian provenance or were raised in those religions. Imagine someone whose parents convert to Hinduism, and raise them in India, but they are half Japanese and English American. They don’t “look” Indian. Brown. Or desi. But if they are raised in India, and practice a form of Hinduism, and speak Indian languages, I have a hard time saying that they don’t have a right to “claim” being desi or brown.

There are obviously many other cases. But I wanted to present these two as opposing and inverted instances, as I think they are the boundary conditions of what desi or brown identity is. People can say what they want about themselves. They could be an Iyer raised in Chennai who claims that they’re really not Indian or desi. Or, someone could be a Russian Karelian who is devoutly Orthodox who claims they Indian. I suspect most of us would think that this is nonsense. To be brown or desi does have boundaries.

But we can make the boundaries crisp and tight. Or broad and loose. For example, to assert that to be desi one has to be a believing and practicing Hindu who is racially South Asian would be a narrow definition.

Or, we can make them broad.

As an American, a broad definition works best for me. My children may not speak a South Asian language, worship Hindu gods, or look particularly “Indian.” But of their eight great-grandparents, four of them were born in British India. They have some claim I think to that heritage and identity, if not as strongly as those genuinely encultured.

February 19, 2019

The deep origins of East African Hunter-Gatherers

Filed under: African Genetics — Razib Khan @ 5:49 pm


PNAs has a new paper out, Genomic evidence for shared common ancestry of East African hunting-gathering populations and insights into local adaptation. From what I can tell this was never a preprint, so it’s all new….

Or is it? Looking closely at some of the populations sampled, I’m about 85% sure that I saw a very early and preliminary analysis of some of these data (probably on a different SNP-chip) at ASHG 2012. I say this because I recall talking to the second author in front of the poster about an obscure hunter-gatherer tribe in Ethiopia that they had sampled. Unlike some graduate students he did not dodge my inquiries by standing away from the poster as if he was not associated with it!

Here is the abstract:

Anatomically modern humans arose in Africa ∼300,000 years ago, but the demographic and adaptive histories of African populations are not well-characterized. Here, we have generated a genome-wide dataset from 840 Africans, residing in western, eastern, southern, and northern Africa, belonging to 50 ethnicities, and speaking languages belonging to four language families. In addition to agriculturalists and pastoralists, our study includes 16 populations that practice, or until recently have practiced, a hunting-gathering (HG) lifestyle. We observe that genetic structure in Africa is broadly correlated not only with geography, but to a lesser extent, with linguistic affiliation and subsistence strategy. Four East African HG (EHG) populations that are geographically distant from each other show evidence of common ancestry: the Hadza and Sandawe in Tanzania, who speak languages with clicks classified as Khoisan; the Dahalo in Kenya, whose language has remnant clicks; and the Sabue in Ethiopia, who speak an unclassified language. Additionally, we observed common ancestry between central African rainforest HGs and southern African San, the latter of whom speak languages with clicks classified as Khoisan. With the exception of the EHG, central African rainforest HGs, and San, other HG groups in Africa appear genetically similar to neighboring agriculturalist or pastoralist populations….

Some of this stuff was vaguely predictable a long time ago. There is a strange tendency in older data and results for hunter-gatherers such as Pygmies and San Bushmen to be closer together genetically against agro-pastoralists and farmers. Additionally, the two most deeply diverged Y chromosomal haplogroups, A and B, tend to be found in African hunter-gatherers in particular. At least at high frequencies.

The main phylogenetic result of this work is some other isolated hunter-gatherers in eastern Africa, more obscure than the Pygmies, Hadza, and San Bushmen, also seem to show deep affinities that set them apart from demographically dominant groups such as Nilotic pastoralists and Bantu farmers.

This is not surprising though in light of ancient DNA. A few years back Pontus Skoglund’s paper showed that there was likely a preexistent relatedness cline in East Africa between the peoples who were present in Ethiopia before the arrival of Eurasians and south toward the ancestors of the modern Khoisan groups in southern Africa.

This work likely confirms the existence of this cline before it was demographically swamped out by migrations triggered by groups which had shifted their modes of production (from hunting and gathering to farming and/or pastoralism). That being said, I am somewhat skeptical of very deep history inferences from these data. In the paper itself, the authors admit that the origins of modern humans in Africa date to ~300,000 years before the present. Skoglund’s data set is from the Holocene, the last ~10,000 years or so.

The authors used a Bayesian framework to make a few concrete inferences:

The maximum a posteriori estimate and 95% credible interval for pairwise divergence time estimates are shown in Fig. 3. The maximum a posteriori divergence time estimates for the Hadza and Sandawe were 13 or 22 kya when accounting for different primary sources of admixture based on STRUCTURE analysis (Fig. 1D) (NC or AA, respectively); these estimates overlap with previous studies (17). The Hadza split times with other populations were older; the divergence time estimates with the Sabue (NC or AA gene flow) were 44 or 61 kya, respectively, and with the Dahalo (NC or AA gene flow) were 55 or 61 kya, respectively. Sandawe population divergence time estimates with the Sabue (NS or AA admixture) were 30 or 52 kya, respectively, and with the Dahalo (NS or AA gene flow) were 50 or 57 kya, respectively. The estimated times of divergence of the Sabue and Dahalo (NC or AA gene flow) were 63 or 72 kya, respectively. These results are consistent with a model in which population divergence between the Dahalo and Sabue and the ancestors of the Sandawe and Hadza occurred >30 kya, whereas the Hadza and Sandawe divergence was more recent. Whole-genome sequence analyses will be informative for more accurately resolving the time of population divergence among EHGs.

There are a few things I’ll note about this. Some of these populations, such as the Sandawe, are clearly the product of recent admixture. This is supposedly accounted for, but who knows what details remained unaccounted. Additionally, a lot of the divergence times are weirdly coincident with the “Out of Africa” migration, ~50,000 years ago. Finally, I have zero confidence that hunter-gatherers in Tanzania and Ethiopia had ancestors in the local region ~50,000 years ago. They may have. But we can’t take for granted that these were static groups. There’s strong evidence that Pygmies have undergone selection for smaller size, so we know that they weren’t in the deep rainforest for hundreds of thousands of years.

Rather than specifics, what I take away from this is that there is a lot of deep structure in East Africa which was swamped out by recent demographic expansion by Bantu farmers. We knew this. But there is a lot more detail here that needs to be explored.

One thing I want to note is that the most common Y chromosomal lineage within Africa is a branch of E1, which diversified ~50,000 years ago. This is nearly fixed in many agriculturalist groups. The Yoruba are over 90% E1b1a. But even the Hadza are 40% E1. Some of this is likely from admixture with Bantus, but some of it is probably from admixture with Cushitic people. There have long been arguments about the origins of this haplogroup. It turns out that the ancient Natufians carry it.

But, it is highly possible that E is indicative of a serious “back migration” into deeper Africa coincident with the “Out of Africa” movement (is origin may have been in North Africa as opposed to West Asia). Several years ago David Reich mentioned offhand that Eurasians may be closest to the Hadza of unadmixed African groups. This is not geographically implausible, but what if the patterns that Reich’s group sees are due to an ancient back migration from the Middle East deep in the Pleistocene? One thing ancient DNA is telling is that many “unmixed” populations do have admixture.

The pattern of deep and ancient structure within Africa is only vaguely understood at this point. Models which infer parameter estimates based on current understandings may give misleading inferences because we are specifying a model that misses major features of the true dynamics. For example, there is evidence for a deeply basal lineage in West Africa, as well as continuous gene flow from West Eurasians well after the “Out of Africa” event.

As they say. “Watching this space” and “developing”….

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