Category: human evolution

Readers’ wildlife photos

December 19, 2024 • 8:15 am

Today is the third and last part of Athayde Tonhasca Júnior’s travelogue, including ancient paintings, from Brazil (part I is here and part II is here).  Athayde’s captions are indented, and you can enlarge his photos by clicking on them. Without further ado:

Back in the day. Way, way back, Part III

JAC: the introduction to part I:

The Brazilian north-eastern hinterland is not a hospitable place for an outsider. Except for a short and intense rainy season, this is a dry, dusty and sizzling territory: a land of the cactus, thorny scrub and stunted trees. The native Tupi speakers called this semiarid region caa (forest, vegetation) tinga (white), and the term was adopted by the Portuguese settlers as caatinga. But the apparent harshness of the landscape misrepresents its ecological importance. The caatinga is a biota found nowhere else in the world, harbouring more than 2,000 species of vascular plants and vertebrates, with endemism in these groups ranging from 7 to 60%. And like every other Brazilian ecoregion, the caatinga has been severely degraded and fragmented. But its plants and animals have one place of refuge: the Serra da Capivara National Park in the state of Piauí. The park is a haven to numerous birds and endangered mammals such as the giant anteater (Myrmecophaga tridactyla), three-banded armadillo (Tolypeutes tricinctus), jaguar (Panthera onca) and other cats, and the maned wolf (Chrysocyon brachyurus).

The 129,140-ha park contains a massif of sandstone sediments formed some 430 million years ago when the whole area was submerged under a sea. The massif, smoothed by water and wind, was once the seabed, and pebble conglomerates on top indicate an overlying beach.

New:

In 1963, Niède Guidon organized an exhibition of prehistoric paintings in São Paulo. She was approached by one of the visitors with some pictures of ‘Indian paintings’ from places near his property in Piauí, a remote and forgotten region in the 60s. Guidon saw right away that those pictures were something completely different. She only managed to visit the area about 10 years later, and thanks to her, Serra da Capivara was discovered by the outside world – including Brazilians.

Pedra Furada (pierced rock), near the place where Guidon’s excavations provided evidence for a much earlier human presence in South America than previously thought:

Zuzu, one of the oldest human specimens found in South America. Assigned as female at discovery, later transitioned to male by researchers. Zuzu died approximately 9,600 years ago (Museu do Homem Americano).

How Zuzu may have looked (Santos & Moraes, 2023):

Superstition helped preserve Serra da Capivara. Tales of eerie voices and floating apparitions meandering through the canyons kept people away (can you see the face profile on the left wall?). Local elders warned youngsters about bad things happening to those who disturbed the ‘Indian paintings’:

Many of Serra da Capivara‘s pre-historic paintings suggest that life among the cliffs and canyons was not peaceful and idyllic. Here we witness a possible murder or execution:

A shagging scene, but not of a vanilla variety. The supporting character on the right hints of a threesome or, ominously, a non-consensual act:

Leaping deer:

Despite having survived for thousands of years, the wall paintings suffer the ravages of weather. The most vulnerable ones have been shielded from running water:

Some of the park’s residents like the ubiquitous coroa-de-frade (friar’s crown, Melocactus zehntneri) are on standby to inflict pain on the absent minded:

A slice of the bottom of the sea. Our minds need training to see things in geological time frames:

A parting view of Serra da Capivara. If you sit here for a while, you’d be taken by the silence. Nothing seems to move, and you only hear your own breathing:

Going home: 300 km to the airport on a mostly empty road, although you need to watch for goats grazing by the roadside. All that changes when you pass the towns along the way: mountains of plastic bags, rubbish and rubble everywhere. Places that don’t do justice to a small paradise hidden in the caatinga heartland:

An ideologically-based and misleading critique of how modern genetics is taught

October 10, 2024 • 9:30 am

Over at sapiens.org, an anthropology magazine, author Elaine Guevara (a lecturer in evolutionary anthropology at Duke) takes modern genetics education to task.  Making a number of assertions about what students from high school to college learn in their genetics courses, Guevara claims that this type of education imparts “zombie ideas”: outdated but perpetually revived notions that prop up biological racism.  Her main topic is race, and she does offer some insights that modern genetics has given us about differences between geographic populations (I prefer to use “populations” rather than “races”), but these insights have been known for a long time. By failing to tell us that the errors earlier biologists have made about race have been refined and, to a large degree, dispelled, Guevara is herself deficient in describing the state of modern genetics.

Click the screenshot to read:

Guevara makes several accusations that, I think, are misleading. I’ll group her misleading conclusions under bold headings (the wording of those is mine). Quotes from her paper, or my paper with Luana Maroja, are indented and identified

1.) Human populations are not as different as we think, and the concept of “race” is incorrect: classical “races” are not genetically distinguishable. Guevara first cites a famous 1972 paper by my Ph.D. advisor, Richard Lewontin, “The Apportionment of Human Diversity“. The paper looked at genetic variation of 17 proteins detected by gel electrophoresis, apportioning the worldwide variation of proteins among individuals within a population, among populations within a classical “race”, and then between seven “races”. He found that of the total genetic variation seen worldwide, 85% occurred among individuals within one geographic population, 8% among populations within a race, and only 6% was found among races.

Thus races were not as genetically different as some people assumed. Lewontin concluded this (bolding is mine):

It is clear that our perception of relatively large differences between human races and subgroups [JAC: note that Lewontin’s “subgroups” correspond to what I would call “populations’], as compared to the variation within these groups, is indeed a biased perception and that, based on randonly chosen genetic differences, human races and populations are remarkably similar to each other, with the largest part by far of human variation being accounted for by the differences between individuals.

Human racial classification is of no social value and is positively destructive of social and human relations. Since such racial classification is now seen to be of virtually no genetic or taxonomic significance either, no justification can be offered for its continuance.

The first paragraph is correct. Later studies using better methods (DNA) have shown that yes, the apportionment of human diversity shows most of it within populations and only a fraction among populations or among “races”.  The classical view that races like “Caucasion”, “Asian” or “Black” showed large and diagnostic genetic differences at single genes was wrong

But the second paragraph is wrong, too, because Lewontin did not raise the possibility (as I’m sure he realized) that small differences among populations (or the groups of populations that constitute classical “races”) can, taken across many, many genes, add up to significant statistical and biological differences. The failure to recognize the power of using genetic data from many genes (we have three billion DNA nucleotides in our genome) is called “Lewontin’s fallacy.” This fallacy was pointed out in 2003 by A.W.F. Edwards and has its own Wikipedia page.

The power of using many genes instead of just an unweighted average of data from individual genes is shown by several things, as Luana Maroja and I pointed out in our paper published in Skeptical Inquirer last year. For one thing, if there were no meaningful genetic differences between populations, you couldn’t use genetic differences to diagnose someone’s ancestry. Yet you can, and with remarkable accuracy, as anyone knows who is aware of their family history and has taken a genetic test like those offered by 23andMe.  My test showed that I have complete Eastern European ancestry, with 98% of it from Ashkenazi Jews, which comports with what I know of my family history. (I also have a small percentage of genes from Neanderthals.)

Now this tells you the area of the world—the population—from which your ancestors probably came.  It doesn’t deal with “races” as classically defined. Yet a multiple-gene analysis using four races that Americans themselves use in self-identification (African-American, white, east Asian, or Hispanic) can indeed be diagnosed with remarkable accuracy. As Luana and I said in our paper (I’ve bolded the money quote):

Even the old and outmoded view of race is not devoid of biological meaning. A group of researchers compared a broad sample of genes in over 3,600 individuals who self-identified as either African American, white, East Asian, or Hispanic. DNA analysis showed that these groups fell into genetic clusters, and there was a 99.84 percent match between which cluster someone fell into and their self-designated racial classification. This surely shows that even the old concept of race is not “without biological meaning.” But that’s not surprising because, given restricted movement in the past, human populations evolved largely in geographic isolation from one another—apart from “Hispanic,” a recently admixed population never considered a race. As any evolutionary biologist knows, geographically isolated populations become genetically differentiated over time, and this is why we can use genes to make good guesses about where populations come from.

And this:

More recent work, taking advantage of our ability to easily sequence whole genomes, confirms a high concordance between self-identified race and genetic groupings. One study of twenty-three ethnic groups found that they fell into seven broad “race/ethnicity” clusters, each associated with a different area of the world. On a finer scale, genetic analysis of Europeans show that, remarkably, a map of their genetic constitutions coincides almost perfectly with the map of Europe itself. In fact, the DNA of most Europeans can narrow down their birthplace to within roughly 500 miles. [See below for the European data.]

You can also identify the “classical” races used in self-identification using some morphological traits. As we wrote:

But you don’t even need DNA sequences to predict ethnicities quite accurately. Physical traits can sometimes do the job: AI programs can, for instance, predict self-reported race quite accurately from just X-ray scans of the chest.

Population differences summed across genes can tell us more, too:

On a broader scale, genetic analysis of worldwide populations has allowed us to not only trace the history of human expansions out of Africa (there were several), but to assign dates to when H. sapiens colonized different areas of the world. This has been made easier with recent techniques for sequencing human “fossil DNA.” On top of that, we have fossil DNA from groups such as Denisovans and Neanderthals, which, in conjunction with modern data, tells us these now-extinct groups bred in the past with the ancestors of “modern” Homo sapiens, producing at least some fertile offspring (most of us have some Neanderthal DNA in our genomes). Although archaeology and carbon dating have helped reconstruct the history of our species, these have largely been supplanted by sequencing the DNA of living and ancient humans.

Finally, there are nearly diagnostic differences between populations in genes that evolved in an adaptive way, like known genes for resistance to low oxygen, short stature or skin pigmentation. Here’s a figure from a 2015 Science paper by Sarah Tishkoff:

None of this would be possible if there were not significant genetic and biological differences between populations.  We did not maintain that there are always diagnostic differences between populations at single genes that can group them into races, but that there are statistical differences in frequencies of variable genes among populations that are biologically meaningful.  Nor did we claim that the classically-defined races are absolutely geographically distinct with little intermixing, or have nearly fixed differences in frequencies of variable genes. That’s not true, and all geneticists realize this now. (But note that even the classically defined “races” generally differ in gene frequencies and in some biological traits to an extent that they can be diagnosed.)

The reality is that we should be dealing with populations, and populations—roughly defined as geographically different groups of people that largely breed among themselves—show diagnostic genetic and morphological differences.

Yet Guevara misleads the reader by relying solely on Lewontin’s paper and neglecting all the work done since that showing that yes, there is diagnostic geographic variation among populations (note that Lewontin implied that the concept of “population” is about as meaningless as “race”). Here are cxcerpts from Guevara’s paper:

Lewontin published his calculations in a short paper in 1972 that ended with this definitive conclusion: “Since … racial classification is now seen to be of virtually no genetic or taxonomic significance either, no justification can be offered for its continuance.” His results have been replicated time and again over the last 50 years, as datasets have ballooned from a handful of proteins to hundreds of thousands of human genomes.

But despite huge strides in genetics research—leaving no doubt about the validity of Lewontin’s conclusions—genetics curricula taught in U.S. secondary and post-secondary schools still largely reflect a pre-1970s view.

This lag in curricula is more than a worry for those in the ivory tower. Increasingly, genomics plays a leading role in health care, criminal justice, and our sense of identity and connection to others. At the same time, scientific racism is on the rise, reaching more people than ever thanks to social media. Outdated education fails to dispel this disinformation.

Leaving “no doubt about the validity of Lewontin’s conclusions”?  Nope.  The apportionment of variation is without doubt, but not his conclusion that populations or races are without biological meaning.

None of the critiques of Lewontin’s paper, including Edwards’s famous clarification, are even mentioned by Guevara. And, in fact, I don’t know of any biologists in post-secondary genetics education who still teach the view that “Race and ethnicity are social constructs, without scientific or biological meaning.” (This is a quote from JAMA reproduced in the Coyne and Maroja paper. And perhaps some people teach this erroneous view, but no biologist that I know of.) That JAMA statement is completely misleading, as I hope I’ve shown above. The delineation and definition of classical races was itself misleading and often tied to racism in the past, but, as we see, even self-identified classical races can be diagnosed through genes or morphology, and generally do fall into clusters using analysis of multiple genes.

The last paragraph of Guevara’s quote above shows the ideological motivation behind her paper: we must dismiss the existence of biological races and genetic differences between populations because it emphasizes differences between humans, and thus could lead to ranking of human populations, and thence to racism.  But, as Ernst Mayr recognized, accepting differences does not mean you have to view groups as being morally or legally unequal. We give a quote by evolutionist Ernst May quote in our Skeptical Inquirer paper:

Equality in spite of evident non-identity is a somewhat sophisticated concept and requires a moral stature of which many individuals seem to be incapable. They rather deny human variability and equate equality with identity. Or they claim that the human species is exceptional in the organic world in that only morphological characters are controlled by genes and all other traits of the mind or character are due to “conditioning” or other non-genetic factors. … An ideology based on such obviously wrong premises can only lead to disaster. Its championship of human equality is based on a claim of identity. As soon as it is proved that the latter does not exist, the support of equality is likewise lost. (Mayr 1963)

Thus, the second conclusion of Guevara is wrong:

2.) “High genetic variation exists within geographic regions, and little variation distinguishes geographic regions.”

Well, that’s sort-of true, but, as we said, that “little variation among geographic regions” can, when added up, diagnose populations sufficiently to not only tell you your geographic ancestry, but also to reconstruct the evolutionary and migratory history of human populations. Guevara dismisses these ancestry tests, though she doesn’t tell us why they are wrong:

Helping the zombie persist, direct-to-consumer genetic tests, like those offered by 23andMe and AncestryDNA, can reinforce misconceptions about human variation. These services have become many people’s primary reference point for human genetics information. To be marketable, the companies must communicate their results in simple, familiar ways that also appear meaningful and reliable. This usually entails simplifying genetic ancestry to bright, high-contrast colors, pinned definitively to geographic regions.

And yet, at the same time, Guevara admires the same kind of data—genetic differences between living populations (as well as “ancient fossil DNA”)—as being of value:

In addition to genomes from living humans, DNA extracted from ancient humans over the past two decades has revealed incredible insights. Across time, past humans frequently migrated, mated with, or displaced people they encountered in other regions—resulting in a tangled tree of human ancestry. The ancient DNA results refute any notion of deep, separate roots for humans in different geographic regions.

Well, there are deep roots for some groups (the Neanderthal lineage, for example, separated form the lineage leading to modern humans about 400,000 years ago), and this comes from both fossil and DNA evidence.  The “tangled tree” may be correct in some ways (we did hybridize with Neanderthals, and other populations exchanged genes to different degrees), but it’s not tangled enough to completely efface the evolutionary history of human populations.

All this leads to a third misleading conclusion:

3) Races are social constructs. Any differences between races are largely caused by racism rather than genes. As Guevara says:

As laid out by a major professional association for biological anthropologists, race is a social reality that affects our biology. For the last several hundred years in the U.S. and other colonized lands, racism has influenced people’s access to nutritious food, education, economic opportunities, health care, safety, and more. As a consequence, and precisely because of the environmental influence on most traits, the social construction of race is a risk factor for many health conditions and outcomes, including maternal and infant mortality, asthma, and COVID-19 severity.

This again shows both an ideological motivation and a misleading conclusion. Even the classical biological races (and even more so worldwide populations) are NOT social constructs, but are associated with genetic, morphological, and adaptive differences.  If races are purely socially constructed, how could you tell them apart in the first place? You need some kind of genetic marker. In the case of racism in America, the differences between African-Americans and whites were “constructed” based on skin pigmentation, hair texture, and other traits—traits based on genetic differences. Those differences served to mark out which people were considered different, and then “inferior”, though, as I said, genetic differences among people say nothing about moral or legal equality. THAT is the lesson that needs to be imparted, not the falsity that there are no genetic differences among groups.

Now Guevara may be correct that the “social construct” view is the one taught, erroneously, in high school and college.  But she’s wrong in thinking that Lewontin’s paper supports that “social construct” view.  In fact, the social construct view is largely wrong, with some exceptions centered on the outmoded view of “classical races”, but it appears to dominate anthropology and the social sciences. Anybody holding that view for either populations or groups of geographically contiguous populations needs to read the Coyne and Maroja paper.

4). Humans aren’t peas.  According to Guevara, Mendel’s work on peas, as taught in school, buttresses scientific racism, too:

I, along with others, am concerned that this focus instills and reinforces a false pre-Lewontin view that humans, like Mendel’s peas, come in discrete types. In reality, early studies of peas and other inbred, domesticated species have little relevance for human genetics.

Indeed, it is of little relevance to human genetics, but I’m not aware of any teacher who describes Mendel’s work—which served to show how genes sort themselves out during reproduction—and uses it to conclude, “See, human races are as distinct as round and wrinkled peas.”

In the end, both races and populations of humans show genetic and evolved morphological differences—less than we thought, say, a hundred years ago—but differences that are still significant in useful ways. To say that races or populations are purely social constructs is simply wrong, and to use Lewontin’s paper to reinforce that conclusion is doubly wrong.

Now reader Lou Jost has argued that Lewontin couldn’t really mathematically partition genetic variation the way he did because Lewontin used the wrong method. Regardless, it’s clear that there is more genetic variation at a given locus within a population than between populations or the groups of populations once deemed “races”.  But in the end there is a tremendous amount of information of biological and evolutionary significance to be gained by adding up the small genetic differences we see between human populations.

To end, here’s a map of genetic variation among populations in Europe, showing how the genetic variation (grouped by principal components analysis) lines up nicely with the geographic variation in populations. That’s because genetic differences evolved between semi-isolated groups of people, and that is why we can tell with considerable accuracy where our ancestors came from

Paper: Gilbert et al. 2022

Geography (populations sampled are in black)

Genetics (grouping of individuals using two axes of a principal components analysis. Look how well the geography (identified by color above) matches the genetics!

 

Andrew Sullivan on the ideological erosion of science and the genetics of “race” differences

September 23, 2024 • 10:15 am

Andrew Sullivan’s latest column (click first headline to read, but I couldn’t find an archived version) is a strange one.  His main point—that “progressives’ think that some scientific research should be ignored because it flouts their ideological conventions—is a good one, and one that Luana Maroja and I made before.

In this piece, Sullivan attacks three of these issues: assumption that there are no evolved differences among races, especially in intelligence; that gender reassignment may not always be a good thing; and, an issue I’ve mentioned before, the falsity of recent claims that black newborns have a higher mortality when taken care of by white rather than black physicians (this fact, falsely imputed to racism, actually reflects that underweight black newborns are preferentially given to the care of white doctors).  Sullivan’s conclusion is that science should proceed untrammeled by ideology:

Let science go forward; may it test controversial ideas; may it keep an open mind; may it be allowed to flourish and tell us the empirical truth, which we can then use as a common basis for legitimate disagreements. I think that’s what most Americans want. It’s time we stood up to the bullies and ideologues and politicians who don’t.

He’s right, but he also commits what I see as a serious error.  He describes recent studies by a crack geneticist (David Reich at Harvard) and his colleagues, studies showing that there has been natural selection on several traits within Eurasian “populations” in the last 8000 years. But then Sullivan extrapolates from those results to conclude there must then have been natural selection causing differences among populations.  Now we know that the latter conclusion is true for some traits like skin pigmentation and lactose intolerance, but we can’t willy-nilly conclude from seeing natural selection within a population to averring that known differences among populations in the same trait have diverged genetically via natural selection rather by culture culture (or a combination of culture and selection).

The hot potato here, of course, is IQ or “cognitive performance.”  This does differ among races in the U.S., but the cause of those differences isn’t known (research in this area is pretty much taboo).So even if there’s been natural selection on cognitive performance within Eurasians, as Reich et al. found, one isn’t entitled to conclude that differences among populations (or “races”, a word I avoid because of its historical misuse) must therefore also reflect genetic results of natural selection.

Here’s what Sully says, and basis it on the bioRχiv paper by Akbari et al. (Reich is the senior author) which you can access by clicking below.

Sullivan (bolding is mine):

But how have human sub-populations changed in the last, say, 10,000 years? A new paper, using new techniques, co-authored by David Reich, among many others, shows major genetic evolution in a single human population — West Eurasians — in the last 14,000 years alone. The changes include: “increases in celiac disease, blood type B, and a decline in body fat percentage, as farming made it less necessary for people to store fat for periods without any food.” Among other traits affected: “lighter skin color, lower risk for schizophrenia and bipolar disease, slower health decline, and increased measures related to cognitive performance.” Guess which trait is the controversial one.

The study was able, for the first time, to show

a consistent trend in allele frequency change over time. By applying this to 8,433 West Eurasians who lived over the past 14,000 years and 6,510 contemporary people, we find an order of magnitude more genome-wide significant signals than previous studies: 347 independent loci with >99% probability of selection.

Not just evolutionary change in the last 14,000 years — but “an order of magnitude” more than any previous studies had been able to show. Gould was not only wrong that human natural selection ended 50,000 years ago — but grotesquely so. Humans have never stopped evolving since we left Africa and clustered in several discrete, continental, genetic sub-populations. That means that some of the differences in these sub-populations can be attributed to genetics. And among the traits affected is intelligence.

The new study is just of “West Eurasians” — just one of those sub-populations, which means it has no relevance to the debate about differences between groups. But it is dramatic proof of principle that human sub-populations — roughly in line with what humans have called “races” — can experience genetic shifts in a remarkably short amount of time. And that West Eurasians got suddenly smarter between 10,000 and 5,000 years ago and then more gradually smarter since.

If the results have no relevance to differences between groups, then why in the next sentence does he extrapolate the results to differences between sub-populations or “races”?

Well, yes, Sullivan does indeed admit that the West Eurasian study (below), showing selection within tjat group, can’t be extrapolated to differences between groups.  But he does so anyway, saying that “it is the dramatic proof of a principle that human sub-populations — roughly in line with what humans have called “races” — can experience genetic shifts in a remarkably short amount of time.

Well, no, it doesn’t really “prove” that.  It’s surely true that 1) if two or more populations show genetic variation in a trait and 2) natural selection ACTS DIFFERENTIALLY in those different populations (or “races” or “subpopulations”), then yes, selection can in principle cause genetic differences among populations.  But this is not an empirical observation, but a hypothetical scenario. It’s almost as if Sullivan wants to use within-population data to show that differences among populations (especially in “cognitive performance”) must, by some kind of logic rather than empirical analysis, also be genetically based, and instilled by natural selection. But he is talking about what is possible, not what is known.

The relevant article below, which is somewhat above my pay grade, shows that Reich’s group used a combination of ancient and modern DNA to look for coordinated changes in the sequences of genes  involved in the same trait. Using GWAS analysis (genome-wide association studies), investigators can find out which segments of the genome are associated with variation in various traits within a population.  This way, for example, you can find out which areas of the genome (I believe there are about 1200) vary in a coordinated fashion with variation in an individual’s smarts (they use “educational attainment” as a surrogate for intelligence.

Click title to read:

Knowing this association, you can then compare the bits of the genome in ancient DNA associated with various traits like those listed above, and then estimate a) whether the bits of the genome that are jointly associated with variation in a trait measured today have changed in a coordinated way (i.e., have the genes affecting body fat in a population today changed over the last 8000 years in a coordinated way, with a decrease in those gene variants associated with higher body fat?); and b) the likelihood that natural selection has changed those bits over time.

Although we don’t, for example, know the “educational attainment” of ancient people, we can see that gene variants associated with higher attainment have increased by positive selection in the past few thousand years, implying that the Eurasian population has gotten smarter.  It’s thus fair to conclude that, within the study population,  there was selection for higher cognitive ability, known to be associated with educational attainment.  Here, for example, are two findings of selection from the paper:

CCR5-Δ32: Positive selection at an allele conferring immunity to HIV-1 infection (panel 7)

The CCR5-Δ32 allele confers complete resistance to HIV-1 infection in people who carry two copies43–45. An initial study dated the rise of this allele to medieval times and hypothesized it may have been selected for resistance to Black Death46, but improved genetic maps revised its date to >5000 years ago and the signal became non-significant47,48. We find that the allele was probably positively selected ∼6000 to ∼2000 years ago, increasing from ∼2% to ∼8% (s =1.1%, π=93%). This is too early to be explained by the medieval pandemic, but ancient pathogen studies show Yersinia was endemic in West Eurasia for the last ∼5000 years49–51, resurrecting the possibility that it was the cause, although other pathogens are possible.

Selection for light skin at 10 loci (panels 8-17).

We find nine loci with genome-wide signals of selection for light skin, one probable signal, and no loci showing selection for dark skin.

Depending on which level of stringency you want to use to identify natural selection on bits of the DNA, Reich’s group found between 300-5,000 “genes” (DNA bits) that have undergone positive or negative natural selection in our ancestors. But remember this: when you are talking about selection on traits, we didn’t KNOW the traits of our ancestors (like “intelligence” or “propensity to smoke” in our ancestors. Instead, what we see is that gene variants affecting those traits in modern populations have changed over time from ancient populations, with gene variants affecting a given trait changing in a coordinated way (i.e., different bits of DNA associated today with “higher intelligence” have generally increased over time).

Below is a figure from the paper showing 12 traits that have coordinated changes in the genes affecting them. Click to enlarge, and note that the traits vary from darker skin color (DNA bits associated with darker skin color declined in frequency, implying selection for lighter skin), waist to hip ratio (genes affecting this ratio declined in frequency), and both “intelligence” and “years of schooling” (both showing strong increases in “smart” DNA over the last 8,000 years).  It’s a clever analysis.

From paper: Figure 4: Coordinated selection on alleles affecting same traits (polygenic adaptation). The polygenic score of Western Eurasians over 14000 years in black, with 95% confidence interval in gray. Red represents the linear mixed model regression, adjusted for population structure, with slope γ. Three tests of polygenic selection—γ, γsign, and rs—are all significant for each of these twelve traits, with the relevant statistics at the top of each panel.

This is a lovely study (it needs vetting, of course, as this is a preprint), but doesn’t buttress Sullivan’s conclusion that changes within a group wrought by natural selection, such as the changes above, mean that differences between populations must also have been caused by natural selection. That’s simply a mistake, or a fallacy resting on confirmation bias. Sullivan insists, though, that he’s just interested in what the facts are, and those facts must play into any societal changes we want to make. (He’s sort of right here, but not completely, but I’ve discussed this issue in a WaPo book review.)

Sullivan:

Why do I care about this? It’s not because I’m some white supremacist, or Ashkenazi supremacist, or East Asian supremacist. It’s because I deeply believe that recognizing empirical reality as revealed by rigorous scientific methods is essential to liberal democracy. We need common facts to have different opinions about. Deliberately stigmatizing and demonizing scientific research because its results may not conform to your priors is profoundly illiberal. And, in this case, it runs the risk of empowering racists. As Reich wrote in his 2018 op-ed:

I am worried that well-meaning people who deny the possibility of substantial biological differences among human populations are digging themselves into an indefensible position, one that will not survive the onslaught of science. I am also worried that whatever discoveries are made — and we truly have no idea yet what they will be — will be cited as “scientific proof” that racist prejudices and agendas have been correct all along, and that those well-meaning people will not understand the science well enough to push back against these claims.

Scientific illiberalism is on both sides. The denial of natural selection by creationists and the denial of carbon-created climate change by some libertarians is damaging to any sane public discourse, but so too is the denial of any human evolution for 50,000 years by critical race theorists and their Neo-Marxist and liberal champions.

Okay, but I wish he’d been a bit more explicit about the limitations of Reich’s study for concluding things about selection among populations or “races”.  Note, though, that he chastises both Left and Right for committing scientific “illiberalism.”

One area in which his conclusions seem more sound, however, involves gender and trans issues:

You see this [scientific illiberalism] also in the left’s defense of “no questions asked” gender reassignment for autistic, trans, and mainly gay children on the verge of puberty. The best scientific systematic studies find no measurable health or psychological benefit for the children — and a huge cost for the thousands of gay or autistic or depressed kids who later regret destroying their natural, functioning, sexed bodies. And a new German-American study has just “found that the majority of gender dysphoria-related diagnoses, including so-called gender incongruence, recorded in a minor or young adult’s medical chart were gone within within five or six years.” Yet the entire US medical establishment refuses to budge.

I should say that my own priors might also need checking. Maybe some, well-screened kids would be better off with pre-pubertal transition. Right now, we just don’t know. That’s why I favor broad clinical trials to test these experiments, before they are applied universally, and why I believe kids should have comprehensive mental health evaluations before being assigned as trans. And yet, as I write, such evaluations are being made illegal in some states, and gay kids are being mutilated for life before puberty, based on debunked science — and Tim Walz and the entire transqueer movement is adamant that no more rigorous research is needed.

Agreed!  I think that Sullivan should have added that studies do show that adults accrue overall benefits from changing gender (at least that’s what I remember). If that’s the case, then he’s made another omission that. if admitted would strengthen his credibility (always admit the caveats with your conclusions!) But I think he’s dead-on right about affirmative therapy for minors.

(h/t: Christopher)

Evidence that modern humans left Africa much earlier than we thought

July 12, 2024 • 11:45 am

The skein of human migrations out of Africa is quite tangled.  We of course evolved in Africa, splitting off from the lineage leading to bonobos and chimps about 5-6 million years ago (mya). The first Homo foray out of Africa was probably Homo erectus, which might have left about 1.75 mya and then spread all the way to eastern Asia by 1.5 mya. Then they died off for reasons unknown. (All of this is tentative and subject to revision after future research.)

Our ancestors also split off from a lineage destined to leave again, at various times estimated from 500,000 years ago to 200,000 years ago. That lineage split into the sister subspecies Neanderthals and Denisovans (I consider them subspecies of Homo sapiens), and perhaps into the tiny species H. floresiensis, which lived on the Indonesian island of Flores (dating is wonky here).

The conventional wisdom is that all of these subspecies and species went extinct until “modern” Homo sapiens made its Big Exit into Eurasia about 50,000-60,000 years ago, proceeding to colonize the world.  Now, as Carl Zimmer reports in the NYT (click headline below or find article archived here)  there’s increasing evidence that modern H. sapiens might have left Africa a lot longer ago: about 250,000 years ago. That’s a substantial revision of our migration out of Africa.

I’ve indented excerpts from the article:

Several new studies, including one published on Thursday, argue that the timeline was wrong. According to new data, several waves of modern humans began leaving the continent about 250,000 years ago.

“It wasn’t a single out-of-Africa migration,” said Sarah Tishkoff, a geneticist at the University of Pennsylvania. “There have been lots of migrations out of Africa at different time periods.”

Those earlier migrations went largely overlooked until now, Dr. Tishkoff said, because the people who moved did not leave a clear fossil record of their existence, nor did living people inherit their DNA.

And here’s the evidence that modern H. sapiens left Africa a lot earlier than we think:

Dr. Paabo’s team also discovered that living, non-African people carry fragments of Neanderthal DNA, a signature of interbreeding from long ago. In May, a team of researchers estimated that Neanderthals and modern humans interbred during a short period of time, between 47,000 and 40,000 years ago.

But some Neanderthal DNA does not fit into this neat picture. The Neanderthal Y chromosome, for example, is more similar to the Y chromosome found in living humans than it is to the rest of the Neanderthal genome.

In 2020, researchers offered an explanation: Neanderthal males inherited a new Y chromosome from humans between 370,000 and 100,000 years ago. But that would have made sense only if a wave of Africans had expanded out of the continent much earlier than scientists had thought.

Researchers have recently found evidence for such an early wave in the genomes of living Africans.

Dr. Tishkoff and her colleagues compared the genome of a 122,000-year-old Neanderthal fossil with the genomes of 180 people from 12 populations across Africa. Previous studies had found no sign of Neanderthal DNA in African genomes. But Dr. Tishkoff’s group detected tiny pieces of Neanderthal-like DNA scattered across all 12 of the populations they studied.

When they examined the size and sequence of those genetic fragments, they concluded that Neanderthals inherited them from early Africans. That meant an early wave of Africans expanded into Europe or Asia about 250,000 years ago and interbred with Neanderthals.

This conclusion depends critically not just on the dating of the Y chromosome and other bits of DNA, but also on the date of the migration of the Neanderthal/Denisovan lineage out of Africa. If, for example, the Neanderthal lineage had exchanged genes with the modern H. sapiens lineage in Africa between 370,000 and 250,000 years ago, and THEN the Neanderthal lineage migrated to Europe, we wouldn’t need to invoke an earlier migration of modern humans out of Africa.  I trust that the dating of the Neanderthal migration out of Africa (600,000 years ago or so) is sufficiently accurate that the scenario I invoked wouldn’t have happened. But as far as I can see, the date of Neanderthal migration out of Africa is contested. I’ll punt and take the attitude that “Popppa knows best” since Tischkoff and Paabo are both excellent researchers.

There’s also another study suggesting early migration out of Africa:

Another group of researchers — led by Joshua Akey, a professor of genomics at Princeton University — tackled the same question with its own statistical method. After comparing the genomes of 2,000 people from across the world with three Neanderthal genomes, they reached the same conclusion.

As Dr. Akey and his colleagues reported on Thursday, modern humans expanded out of Africa and interbred with Neanderthals between 200,000 and 250,000 years ago.

But Dr. Akey’s team also found evidence for yet another early wave. By comparing the genomes of young and old Neanderthal fossils, they concluded that another group of people migrated from Africa between 120,000 and 100,000 years ago.

As Steve Gould once said, he always prepared for his class on human evolution by throwing away all his notes from the previous year’s lecture and rewriting his spiel.  This is how fast things change, particularly now that Paabo and colleagues pioneered the study of hominin fossil DNA.

One question remains:  if modern H. sapiens really did leave Africa between 370,000 and 100,000 years ago, what happened to them?  One thing we do know for sure from copious DNA and skeletal and artifact dating is that all modern humans descended from a group of ancestors that left Africa around 60,000 years ago. There’s very little doubt about that.

This means that those earlier migrants didn’t leave descendants; they went extinct and are ex-hominins, singing with the choir invisible. What happened? The article suggests that “African populations built up cultural knowledge that led them to make new inventions, like arrows, and adapt to new places more successfully.”  The older H. sapiens then would have been outcompeted or even killed off by the new arrivals. As usual, we don’t know, nor do we know why the Neanderthals and Denisovans (or, for that matter Homo erectus) went extinct.

It’s a good thing I’ve stopped teaching my lecture on human evolution (I got only 1.5 hours on this in my short Evolution segment), as I’d have trouble keeping up with these changes.  There are few human remains and dating is imperfect, so what’s sure to happen is that the story above is likely to be revised—except for the part that all living humans are brothers and sisters who evolved from a band of ancestors who left Africa a few tens of thousands of years ago.

*********************

Here’s a “classic” Neanderthal skull from Wikipedia, labeled this way:

La Chapelle-aux-Saints 1 (“The Old Man”) is an almost-complete male Neanderthal skeleton discovered in La Chapelle-aux-Saints, France by A. and J. Bouyssonie, and L. Bardon in 1908. The individual was about 40 years of age at the time of his death. He was in bad health, having lost most of his teeth and suffering from bone resorption in the mandible and advanced arthritis.

Neanderthals didn’t live very long. Poor guy!

Luna04, CC BY-SA 3.0, via Wikimedia Commons

New findings about the Denisovans

July 5, 2024 • 11:45 am

We’ve known about the Denisovans for about 15 years, since part of a finger was found in a Russian cave (the “Denisova Cave“) in 2008 and wasw published two years later.  They were a hominin subspecies like Neanderthals. I consider these groups subspecies of H.sapiens because they both interbred with H. sapiens and left fertile offspring. Denisovans lived in Asia from about 300,000 to 25,000 years ago. (They may also have bred with Neanderthals.)  They are considered a sister taxon to Neanderthals, which means that these two groups shared a common ancestor that had already branched off from the ancestor of “modern” H. sapiens.

Wikipedia gives a useful table of all the known remains of Denisovans, which are judged as a distinct group from DNA sequencing. We have small bits of bone, including teeth, parietal bones, mandibles, and limb bones (and now, according to the Nature article below, a rib bone) from the three locations—all caves—shown below from the Wikipedia map shown below:

And here’s a picture of the Denisova Cave in Russia where it all started:

Xenochka, CC BY-SA 4.0, via Wikimedia Commons

Here’s a diagram of the route the Denisovans took as they colonized Siberia and SE Asia from the Middle East, as well as a “family tree” on the right showing the sister-group relationship of Neanderthals and Denisovans (the figure presumes that the common ancestor of the two was a different species, Homo heidelbergensis, which, confusingly. has been considered a subspecies of H. erectus or even H. sapiens.

John D. Croft at English Wikipedia, CC BY-SA 3.0, via Wikimedia Commons

Just as many Westerners have some Neanderthal DNA (I have a bit among my Ashkenazi genes), so some Asians and people from Oceania have Denisovan DNA.  This shows the hybridization I talked about above. And if two groups meet, mate, and produce fertile hybrids, they’re considered by evolutionary biologists to be subspecies, not species. Unless, that is, they’re hominins, for paleobiologists love to split names and create new species, a practice that produces more excitement and fame than simply saying “we found a new subspecies of Homo sapiens.”

Well, we’ve known about the Denisovans for a while, so what’s new? This news report from Nature (click to read) gives us a bit more information, like what kind of food they ate, as well as reporting on a new Denisovan rib bone found this year.

The results aren’t that thrilling to me, but many people thrive on human paleobiology, and so here are some extracts from the news:

When life got tough, the Denisovans got tougher. The enigmatic ancient humans hunted birds, rodents, even hyenas, helping them to thrive high on the Tibetan plateau for well over 100,000 years.

Those conclusions emerge from a study of thousands of mostly tiny animal bones that provide an insight into life at Baishiya Karst Cave in China1 — only the second archaeological site known to host Denisovans, after the Siberian cave that gave the group its name. Denisovans are a sister group to Neanderthals, and might have once lived across Asia.

Many of the cave remains could be identified only by their protein signatures. This included a rib bone that represents a new Denisovan individual, one of just a handful known.

“Denisovans are dealing with the full suite of animals they’re surrounded with in order to survive in this quite harsh landscape,” says Frido Welker, an archaeological scientist at the University of Copenhagen who co-led the study, published in Nature on 3 July. “It’s at high altitude. It’s cold. It’s not a nice place to be as a hominin.”

The article they’re discussing, a new one also in Nature, is below: click on the screenshot to read it:

And here’s the paper’s abstract, which discusses not only the discovery of a new rib bone from the cave in Tibet, but also some scratches on associated animal bones, indicating that they’d been processed for food, presumably by Denisovans:

Using zooarchaeology by mass spectrometry, we identify a new hominin rib specimen that dates to approximately 48–32 thousand years ago (layer 3). Shotgun proteomic analysis taxonomically assigns this specimen to the Denisovan lineage, extending their presence at Baishiya Karst Cave well into the Late Pleistocene. Throughout the stratigraphic sequence, the faunal assemblage is dominated by Caprinae, together with megaherbivores, carnivores, small mammals and birds. The high proportion of anthropogenic modifications on the bone surfaces suggests that Denisovans were the primary agent of faunal accumulation. The chaîne opératoire of carcass processing indicates that animal taxa were exploited for their meat, marrow and hides, while bone was also used as raw material for the production of tools. Our results shed light on the behaviour of Denisovans and their adaptations to the diverse and fluctuating environments of the late Middle and Late Pleistocene of eastern Eurasia.

Here, from the paper, is a human-cut bird wing bone showing the scratches, probably made when feathers were removed. This happens to be a golden eagle. How did they catch it?

(from the paper): Aquila chrysaetos right humerus (layer 4) with superficial and straight cut mark clusters, associated with the removal of feathers

And here from the paper is a photo of the rib bone from a Denisovan also found in the Tibetan cave, along with a phylogeny showing that the rib is closely related to a Denisovan mandible found in the same cave.  It’s not really earth-shaking that a Denisovan rib would be genetically similar to a Denisovan mandible found in a different level of the same cave, but it does add to the specimens we have. Note as well that Denisovans and Neanderthals are, again, placed by DNA analysis as sister groups: each other’s closest relatives.

(From paper): a, Photograph of the Xiahe 2 specimen. Scale bar, 1 cm. b, Phylogenetic tree for the Xiahe 2 specimen and reference proteomes. Support values at nodes are shown for the maximum likelihood and Bayesian analysis, respectively.

A summary from the News & Views piece of how scientists decided which species the animal bones came from (they used protein sequences from collagen rather than DNA to do this), and which animals they ate:

Proper excavations of the cave revealed more signs of occupation: dirt from the site dating to between 100,000 and 45,000 years ago contained DNA sequences from maternally inherited cell structures called mitochondria, matching those of the Denisova Cave remains. The dig, led by archaeologist Dongju Zhang at Lanzhou University in China, also uncovered thousands of mostly fragmentary animal bones.

To identify more than 2,000 of these remains, Zhang, Welker and their colleagues chemically analysed collagen protein signatures, which vary between animals. Especially common were caprines (the subfamily that includes goat and sheep) as well as wild yak, horses and gazelle. Carnivores, including wolves and foxes, also turned up in the mix.

Many of the bones from the cave, including those of hyena, caprines and golden eagles (Aquila chrysaetos), contained cut-marks and other signs of human predation. Even rodents and hare were probably hunted: a marmot (Marmota) leg bone was split open, potentially to harvest its marrow. Such small, speedy animals wouldn’t have been easy to catch, says Zhang, and bringing down carnivores such as hyenas would have taken moxie.

And here’s the Tibetan cave, Baishiya Karst Cave.  It’s no wonder they call these hominins “cavemen”. Where else could you get shelter from the rain and wind and a place to process your catch? And cook it, too, for there’s evidence that both the Denisovans and the Neanderthals could probably make fires.

What more do we know now? Well, we know what the Denisovans ate, which is really no surprise. Callaway tries to give his piece more oomph by saying that we now know the Denisovans’ “survival secrets”, but of course they had to eat something. But knowing what they ate is better than nothing. And we also have more bones, though as yet they haven’t yielded much new information. There’s more to come as excavations proceed, but the N&V ends rather lamely:

. . . . scientists’ picture of Denisovans is becoming less opaque thanks to information gleaned from dirt and shards of bone subjected to cutting-edge DNA and protein analysis, says Brown. “Denisovans are essentially, at the moment, a biomolecular population.”

The remains Zhang and her colleagues analysed are from pre-pandemic excavations of Baishiya Karst Cave. But the researchers are now back excavating the enormous cavern, hoping to find more insights into Denisovan life. “We haven’t reached the bottom,” says Zhang.

Perhaps I’ve gotten jaded, for the discovery of a new subspecies of humans in Eastern Asia, one that probably went extinct like the Neanderthals, truly is a surprise.

Mayan human sacrifices from ancient bones show genetic relatedness among those killed (and other stuff)

June 17, 2024 • 9:30 am

This new paper in Nature gives a rare picture of human sacrifice among ancient Mayans from the Yucatán peninsula in Mexico.  Paleoanthropologists had found remains before, mostly children, preserved by being tossed in sacred cenotes (wells), but this group of 64 ancient individuals was not only collected, but their DNA was analyzed from the ear bones, giving surprising results about genetic relatedness.

As with the Aztecs, human sacrifice was a fixture of ancient Mayan society, though the people killed (in this case, children) were probably captives rather than residents of the place where the killers lived. Sacrifice could have occurred via either decapitation, extraction of the heart from living individuals, or killing with arrows.

Click below to read the piece, or find the pdf here.  

The figure below shows where the remains were found: in a chultún (an underground cistern) next to an airport runway near the ancient Mayan city of Chichén Itzá (now a World Heritage Site), which flourished between about 600 and 1200 A.D. This map gives the location:

(From the paper) a, Location of the Maya region in the Americas. b, Geographical locations of Chichén Itzá and Tixcacaltuyub in the Yucatan Peninsula. c, Stratigraphy for the chultún and the adjacent cave in which the burial was found (adapted from ref. 4). d, Location of the chultún within the archaeological site of Chichén Itzá and its relation to El Castillo (adapted from ref. 10). Modern roads are marked in light grey; the chultún abuts an airport runway.

They found the bones of 64 individuals, carbon-dated as being from the 7th to the 12 centuries AD. How did they know how many individuals were represented in their sample? Because they recovered 64 left petrous parts, the bit of the skull’s temporal bone that surrounds the inner ear (this bone, sequestered away from the outside of the skull, is often used to extract ancient DNA).  64 left petrous bones means 64 individuals.

First, every one of the individuals was a male between 3 and 6 years old, showing that the Mayans preferred to sacrifice young boys. Why? It’s not clear, but there’s speculation that sacrifices helped local maize crops flourish (the method of sacrifice wasn’t specified in the paper).  However, other sacrificed individuals recovered, as in the famous sacred cenote, have been mixtures of males and females, but also overrepresented with children. The authors don’t speculate why, in this location, only boys were killed.

The ancestry of the sacrificed individuals was compared among each other, as well as to 68 individuals of Mayan descent living the nearby town of Tixcacaltuyub. One surprising finding was that those sacrificed included two pairs of identical (monozygotic) twins (easily seen in DNA, which is identical among two different earbones).  The authors note that twins held a special position in Mayan mythology.  But, as the plot of “pairwise mismatch rates” shows below), 11 pair of individuals were “close relatives”, represented by the hollow diamonds (the twins, with a mismatch rate of zero, are the two pairs of twins.  The authors speculate (see below) that the individuals came from a single big event of mass killing.

The paper doesn’t say how “close” the “close relatives were”, or whether they were contemporaneous, like brothers, but given the age of the individuals, it seems likely that the related pair members came from the same family.

(From paper): e, Genetic pairwise mismatch rate (PMR) for child pairs in the chultún identifies 11 close relative pairs (hollow diamonds), including two pairs of monozygotic twins (highlighted in grey). A low overall PMR for unrelated individuals (black triangles) confirms low genetic diversity in the population; only pairs with PMR < 0.20 are visualized in the plot. See Supplementary Fig. 2 for individual annotations.

The comparison of the DNA of the sacrificed children with that of living people in Tixcacaltuyub, as in the principal-component cluster graph below, showed that the sacrificed individuals )”YCH”, dark purple stars) fell into a cluster of Native Americans, other Mayan individuals, people from Belize, and individuals from the nearby town (“TIX”, light blue stars), and were considerably different from individuals in Africa, Asia, and Oceania, as expected. (This shows diagnostic genetic differences between geographic groups, demonstrating that the idea of “races”—defined as “diagnostically genetically differentiated populations”—is not purely a social construct, but contains biological information.)  However, the ancient sacrificed individuals, which also had a dollop of genes from the Caribbean, didn’t particularly cluster with the present day Mayans living nearby, who had their own admixture of genes from Africa and Europe, perhaps reflecting turnover of populations over time. In the sixteenth century there was a big poulation bottleneck, perhaps due to diseases introduced by Europeans. In fact, this bottleneck reduced the population of what is now Mexico by 90%!)

(From paper): (From paper): a, PCA showing ancient Chichén Itzá (YCH) individuals and present-day Tixcacaltuyub (TIX) in a worldwide PCA plot.

One other bit of information. We are able, looking at contemporary DNA sequences of a population, to judge whether natural selection is acting on genes or groups of genes. If variable genes such as the HLA (“human leukocyte antigen”) genes involved in immune response show coordinated variation (that is, variant “A” of one gene tends to co-occur with variant “B” of another gene in individuals), this gives evidence that selection is acting on groups of genes—in this case genes affecting immunity. The authors identified several HLA variants that look like they were subject to selection, and also tested some by making copies of sequences of some HLA variants and seeing how strongly they bound to proteins derived from Salmonella bacteria (strong binding means that the HLA proteins were reacting and presumably neutralizing the bacterial proteins). The authors suggest that the selection acting to promote the rise in frequency of some HLA variants was due to typhoid or paratyphoid-like infections.

The upshot:  Although the data from HLA genes does indicate that there was selection for immunity in both ancient and historic times, what I find most interesting is that the sacrifice involved children, all male children, and many were close relatives. This, at least, gives us a pretty strong sociological picture of one aspect of ancient Mayan culture. To quote the authors,

In comparing the subadults in the chultún to other ancient and present-day populations in the Maya region, we find evidence of long-term genetic continuity, which also suggests that the sacrificed children and sibling pairs at Chichén Itzá were obtained from nearby ancient Maya communities. Among present-day individuals at TIX, we detect evidence of European and African admixture since the Contact period.

and

Overall, 25% of the children had a close relative within the assemblage, suggesting that the sacrificed children may have been specifically selected for their close biological kinship. Moreover, this may underestimate the true number of relatives present in chultún as only 64 of the estimated 106 individuals in the chultún had a preserved petrous portion of the left temporal bone available for analysis. The further finding that the closely related children in each set seem to have consumed a similar diet and died at a similar age suggests that they have been sacrificed during the same ritual event as a pair or twin sacrifice.

and, finally,

The discovery of two sets of identical twins, as well as other close relatives, in a ritual mass burial of male children suggests that young boys may have been selected for sacrifice because of their biological kinship and the importance of twins in Maya mythology. We show that, at a genome-wide level, the present-day Maya of Tixcacaltuyub exhibit genetic continuity with the ancient Maya who once inhabited Chichén Itzá and we demonstrate through several lines of evidence the involvement of the HLA region in a pathogen-driven selection event(s) probably caused by infectious diseases brought into the Americas by Europeans during the colonial period.

The interest of the Mayans in identical twins reminds me of Josef Mengele in Auschwitz, who also took a particular interest in twins, but in his case he did gruesome experiments on them before killing them.

Still more about the frequency of women hunting

June 11, 2024 • 11:30 am

A while back, the paper by Anderson et al. appeared in PLOS One, and caused a bit of a stir in the press because of its claims that women contributed far more to hunting in various societies than anthropologists thought.  The metrics involved what proportion of foraging societies women participated in hunting (79%) and in what proportion of societies women hunted “large game” (33%). This was seen as surprising, but was also sold in the media as showing that women had been unfairly denigrated as the “weaker sex”, doomed to stay home and take care of babies, gathering plants and roots, and only rarely doing the “man’s work” of killing animals.  (Of course a sexual division of labor says nothing about inferiority or superiority of the sexes only that they do different things, which are equally important in keeping society going.)

Click the title to read this paper if you haven’t already:

But then a group headed by Vivek Venkataraman (he’s at the University of Calgary) carefully scrutinized the data used and conclusions advanced by Anderson et al.,  and published a paper in bioRχiv which showed that the Anderson et al. paper was shoddy, containing a number of methodological and numerical errors, all of which conspired to make Anderson’s conclusions false: women appeared to hunt much less than men in both senses. (Note that the rebuttal is very polite, a model of how rebuttals should be written.

Here, for example, is a tweet I posted then listing the many problems with Anderson et al.

I wrote about Venkataraman’s paper on this site, but of course then it was a preprint that had not yet been published, so it didn’t have the imprimatur of publication. Now it has appeared, which i found after reader djc mentioned in a comment that it was accepted in a respectable journal, Evolution and Human Behavior.  The paper, which is essentially the same as the preprint, can be found in published version (well, as a corrected proof in press) by clicking on the link below, or accessing the pdf here:

I’m not going to reproduce all the criticisms I and others leveled at Anderson et al.  What’s new in the published paper is a figure that summarizes all the issues that Venkataraman et al. find with Anderson et al.’s data (click to enlarge):

The conclusions, if the second paper is right, is that women hunted far less often than Anderson et al. concluded, both in the frequency of foraging societies in which women hunted and the frequency of such societies in which women hunted large game.  The related conclusion is that the Anderson et al. paper was not thoroughly reviewed (I’ll give the reviewers a break here: it would be a lot of trouble to look up some of the original data), and at the very least Anderson et al. were inexcusably sloppy. At the most they could have even been tendentious, tweaking and massaging the data so it looks like women hunted more than they did. Here are two paragraphs from the second paper showing the problems of the first:

Insufficient search for source material:

Fourth, though Anderson et al. (2023) investigated each society “by searching through the original references cited in D-PLACE (Binford, 2023; Kirby et al., 2016), and by searching digitized databases and archives,” there are instances in which well-known authoritative sources were not consulted. For example, Anderson et al. (2023) coded the Batek of Malaysia as having female hunters based on Endicott (Endicott, 1984). However, a more recent book by the same author provides quantitative information on female contributions. Endicott and Endicott (2008) wrote: “Still, women procured 2 percent by weight of the animals hunted by nonblowpipe methods and 22 percent of all bamboo rats.” Women procured no animals using the blowpipe (Table 4.1, p. 76) (Endicott and Endicott, 2008). The!Kung were also coded by Anderson et al. (2023) as having female hunters. Yet in her famous ethnography Nisa: The Life and Words of!Kung Woman, Shostak (1981, p. 220) wrote: “!Kung women cannot be considered hunters in any serious way…” A similar case prevails for the Tsimane horticulturalists of Bolivia. The authors cite Medinaceli and Quinlan (Medinaceli and Quinlan, 2018), but they ignore a recent case study on Tsimane women hunting (Reyes-García et al., 2020).

Pseudoreplication:

The fifth issue concerns pseudoreplication, in which the same case is counted more than once. This leads to inflated and inaccurate estimates. There are several examples. The!Kung and Ju/’hoansi are treated as independent points, but these terms refer to the same population (Lee, 1979). The same holds for the Agta and Ayta of the Philippines (Goodman et al., 1985). Moreover, the Efe, Sua, Mbuti (BaMbuti), and Bambote, and the Mardujara and Martu (Martu), are each counted independently despite being members of closely related groups (Bahuchet, 2012; Myers, 1979). We recognize that these errors by Anderson et al. (2023) are not deliberate. Indeed, in at least one case it may be valid to count these as independent data points. The Efe and Mbuti live nearby but are known to have divergent hunting strategies. The Efe are traditionally bow hunters, whereas the Mbuti are traditionally primarily net hunters (Bailey and Aunger Jr., 1989). However, due to the potential for cultural autocorrelation to inflate the frequency of women’s hunting, such decisions should be acknowledged and justified.

These are just two of many problems, and I’d be really embarrassed if I were an author on the first paper. But perhaps Anderson et al. will reply, though I think Venkataraman, given that they use quotes, have them dead to rights.

But really, the Anderson et al. paper got a lot of publicity because it was considered “feminist,” showing that women did more hunting than previously thought, with the implication that anthropologists, because of an anti-female bias, unduly neglected women’s hunting.  Unfortunately, that kind of popular analysis is misguided, since women, even if they hunt less often than men, are not inferior: they just have a different role, and one that is essential in preserving societies and cultures.

And I predict that the rebuttal of that paper will probably be ignored by the press, simply because it dismantles a conclusion that was considered “progressive”.  I hope not, but we shall see.  But anyone calling the second paper “anti-feminist” is dead wrong; it’s just correcting the science, and it says nothing about how we regard women’s rights and value.

UPDATE: Prediction verified: see comment #2 below by one of the authors of the second paper.

h/t: David