Human Biodiversity: A guide

Darwin’s revolutionary scientific paradigm...

Written by Bo Winegard.

There is, however, no doubt that the various races, when carefully compared and measured, differ much from each other…

— Charles Darwin

When Charles Darwin’s theory of natural selection was first forwarded, it challenged a suite of sacred values. Primarily, it challenged the notion that an omnipotent and benevolent god specially created humans. Today, Darwin’s theory challenges a different suite of sacred values, of which perhaps the most important is that all human populations have roughly the same distribution of socially valued traits. Now, as then, the clash of science and sacred narrative is causing a cacophonous dispute that is often divisive and unenlightening. Authors have written books denouncing scholars who strive to understand human variation, accusing them of having malignant motives and of, ipso facto, promoting racism. A new term (or an old term appropriated for new purposes), “race science” has been used to denigrate the study of human diversity.

Although it’s understandable that many would react with hostility to what might appear to be a frontal assault on a hallowed moral principle (that all human groups are equal), it’s also unedifying and unfortunate. For the truth of human variation, although undeniably shocking to many mainstream pundits, is less corrosive, less incendiary than current norms maintain. Human populations are likely different in more than superficial ways. Not only do they have different skin colors, hair textures, body structures, and proportions of blood types, they also likely have different psychological propensities and sensibilities. But nothing cataclysmic follows from this. It simply means that we inhabit a world that is diverse, with sundry types of individuals and populations.

Whereas earlier scholars of human diversity sometimes argued that modern humans evolved independently in various regions, most scholars today believe that all modern humans stem from ancestors who evolved in East Africa somewhere between 300,000 and 100,000 years ago. This means that instead of evolving in disparate areas around the globe, humans from this one population migrated to all of them. According to researchers, humans likely began this long exodus from Africa into the Near East and across the planet approximately 50,000 years ago. By roughly 45,000 years ago, they had spread throughout much of Asia, Europe, and Oceania; and by 15,000 years ago, they had spread into America. In other words, humans, a small, unimpressive ape, had managed through ingenuity, luck, perseverance, and, perhaps most importantly, culture, to occupy an enormous and variegated territory from the sun-blasted land of the equator to the frozen tundra of Northern Eurasia.

But the story of human evolution and migration is not so simple as some scholars once thought. Humans did not stop to dwell permanently in one location once they decided they liked the weather, the game, or the freedom from incessant warfare with other humans. Rather, they constantly migrated and mixed with each other, exchanging genes and cultural traditions. The people who inhabit Europe today, for example, are a genetic mélange of various populations, including Western European hunter-gatherers and Levantine farmers. The same is true across the globe. The idea that human groups migrated to different territories 40,000 years ago, split genetically from other human populations, and continued an unbroken, unmixed path of descent to modern populations is completely erroneous. Nevertheless, it is true that the humans who left Africa encountered radically different environments and were often exposed to them for many thousands of years (hundreds of generations). Some of the challenges these environments posed were solved culturally, but some were also solved genetically. And, therefore, humans around the globe, although sharing many recognizable characteristics and propensities, are different from each other because of both cultural and biological adaptations.

Perhaps the most obvious example is that humans have myriad different colors of skin. Although not perfect, there is a strong correlation between the intensity of regional UV radiation and skin color such that dark skin is related to more intense radiation. Thus, the average Swedish person has fair skin; the average Iranian has olive skin; and the average Sub-Saharan African has dark skin. The reasons for these skin color differences are not entirely clear, but researchers have forwarded many reasonable hypotheses. Dark skin, for example, appears to function as a kind of sunscreen which protects against cutaneous and systemic folate degradation. And light skin appears to allow for more pre-vitamin D3 synthesis in climates with very little sunlight in the winter months, although some researchers have forwarded other hypotheses, with some contending that sexual selection may have played a role. 

Human populations also have many more intriguing adaptations to different environments and challenges. Some populations have adaptations to extreme altitude, for example. At very high altitudes, those of around 2,500 meters or more, low pressure creates significant challenges to human health, reproduction, and even survival. Even visits to such places can result in temporary, acute “mountain sickness”, and those who reside in such places can experience chronic mountain sickness that is injurious to reproductive fitness. Nevertheless, there are some human populations who permanently dwell in high-altitude environments such as the Qinghai-Tibetan Plateau and the Semien Plateau in Ethiopia. In different populations, the exact physiological adaptations are different and the details get complicated pretty quickly. The important point is that several human populations have adapted (genetically) to high altitudes and some even appear to have “borrowed” their adaptations from Denisovans or Denisovan-related individuals.

Not only did migrating humans encounter novel environmental and climatological selection pressures, but they also created their own. Like spiders, beavers, and birds, humans change their own environments in dramatic ways, creating cultural niches which they then had to navigate. For example, roughly 10,000 years ago, humans began domesticating plants and animals and some developed the ability to digest lactose, the sugar in milk, into adulthood. The capacity to digest a rich and reliable source of calories likely conferred an enormous reproductive advantage upon those who developed it. This ability likely evolved independently among many groups, including those in Europe and Africa, suggesting that it indeed conferred a selective advantage for human populations who had domesticated milk-producing animals.

The story related above, although still disputed by some, is not terribly controversial. Mainstream textbooks have laid it out (with many other examples of human biological diversity), and few scholars would contradict the general argument that some human populations have unique adaptations to environmental challenges. However, things get much more controversial when one attempts to apply this same Darwinian logic to the human mind. Because of this controversy, there is very little mainstream discussion about potential psychological variation among humans caused by recent evolution. The widely available textbooks on human biological diversity, for example, all reject the hypothesis that human groups vary psychologically for genetic reasons and often accuse those who have argued otherwise of invidious prejudices. And the few scholars courageous (or bullheaded) enough to promote this idea publicly have been fustigated and often fired for their efforts. (Charles Murray’s Human Diversity is a new, laudable exception.)

This is very odd, to say the least, because the human brain is an organ just like any other and is not somehow insulated from the forces of natural selection by the skull. What applies to the human body also applies to the human brain. And, in fact, because humans are particularly intelligent creatures, surviving through cleverness and ingenuity more than strength or agility, the brain was likely an especially important target of selection.  

What is perhaps even more odd is that many evolutionary psychologists — those who study humans from an evolutionary perspective — have also denied that human populations vary psychologically, contending instead that human populations share a similar psychological nature across the globe.

The evolutionary psychology argument against human psychological variation relies on the claim that there hasn’t been enough time for humans to evolve novel mental mechanisms. The human skull, according to John Tooby and Leda Cosmides, two prominent evolutionary psychologists, houses a “stone age” brain, one that likely hasn’t changed in important ways for 50,000 years. But this is either wrong or misleading. Nobody believes that human populations evolved novel mental mechanisms; rather, some believe that different environmental and cultural challenges slightly altered existing mental mechanisms. The same appears true of many different animals. Consider the domesticated cat. There is from one perspective a common feline nature. Cats as a species have recognizable behavioral tendencies. However, there are also heritable breed differences in behaviors. Small, correlated brain changes led to unique breed propensities, most probably within the last 4,000 years. There is no reason the same wouldn’t also hold for humans in the last 50,000 years.

Others — those generally skeptical of evolutionary psychology — have argued that this last claim is incorrect because humans’ one supreme adaptation is the behavioral plasticity that our high intelligence allows. Although it is certainly true that humans are remarkably flexible, intelligent creatures, it seems implausible that the humans who evolved in Eastern Africa had exactly the right amount of intelligence and behavioral plasticity that permitted their brains to remain impervious to further selective forces in the wildly different environments and cultural systems they went on to inhabit. In fact, if those environments and cultural systems posed different challenges and rewarded different traits and behaviors for long enough, then natural selection would have inevitably changed the frequencies of genes related to those traits and behaviors.

Consider a plausible hypothetical.

Imagine that cooperative behavior is more important in colder climates because humans are more dependent on meat, storage, and group sharing for calories in environments with long winters. (To be clear, this is a hypothetical example. The actual relation between effective temperature and hunting and gathering is complicated and that between cooperation and effective temperature is even more complicated. However, an example like this is certainly possible. It is the logic that is important here.) And suppose that humans have occupied cold environments for many thousands of years (a hundred generations or more). Under such conditions, those humans who were slightly more predisposed to, and better at, cooperating would likely have had better reproductive success. And, over many generations, that would have led to an alteration of the gene pool and a subtle but likely noticeable shift in personality traits. Nothing about this should be controversial; it is just a natural, indeed inevitable, consequence of taking Darwinism seriously.

Of course, the next question, if the above is accepted, is do we have any good evidence that there are genetically caused differences in psychological traits? The answer, unfortunately, is it depends upon whom you ask. Because group differences are such a contentious topic, often inspiring furious denunciations and denials, some researchers would vehemently contend that there is no such evidence. But, at this point, such a claim is untenable. Suggestive evidence of psychological differences among human populations is abundant, even if most mainstream scholars choose to ignore or deny it. This does not mean that any specific claim about human psychological variation will turn out to be true. It simply means that the literature is teeming with evidence for (partially) genetically caused human psychological diversity.

For example, there is some evidence that Northeast Asians are more collectivistic, more interdependent, than other human populations because of both culture and genetics. Jon Y. Chiao and Katherine D. Blizinsky, for example, found a relation between a genetic polymorphism and collectivism that was more common among Northeast Asians than Europeans. They argued that certain existing social sensitivities might cause Northeast Asians to create more collectivistic cultures, partially reversing traditional causal accounts of the relation between culture and human nature. (Although the basic argument Chiao and Blizinsky forwarded about Northeast Asian emotional propensities appears plausible, one should be skeptical of studies that find a relation between a single polymorphism and some personality characteristic because so many such studies have failed to replicate.) 

Other researchers have made similar arguments about Northeast Asians, relating their emotional propensities to harsh environments and staple crops that required them to cooperate more closely (thus becoming more interdependent) than other populations. This last argument (about staple crops) did not refer explicitly to genetic differences, but if such conditions persisted for hundreds or even thousands of years, then there is no reason they wouldn’t have altered the gene pool by favoring certain psychological propensities over others.

There is also copious (but not conclusive) evidence that human populations vary in intelligence, as measured by IQ tests, partially because of genes (this view is often called “hereditarianism”). Because this is the most incendiary of any of the proposed traits that vary among populations, the simple fact that the overwhelming abundance of evidence supports a partial genetic etiology is hidden like a soft violin beneath the booming brass of moral outrage and character assassinations. In a recent work, Russell Warne forwarded five lines of evidence that support the hereditarian hypothesis: (1) Spearman’s hypothesis; (2) Measurement invariance; (3) Relationship of within and between-group differences; (4) GWAS data; (5) Admixture studies. This article is too short to deal with this topic with justice, since it is quite complicated and technical. The point here is simply that evidence strongly supports the contention that group differences are partially genetic in origin.

Of course, none of the evidence is decisive. And there is no need for excessive confidence about what researchers will find when they study human psychological variation in earnest. But it is suggestive. And it is coherent with Darwinism, the single most productive research paradigm in the biological and psychological sciences. Thus researchers should study it and discuss it more candidly.

However, it is important not to be naïve. Some of the findings of a science of human variation will violate modern sacred values. Human populations will likely differ on socially consequential traits such as intelligence, criminality, agreeableness, openness, ambitiousness, athleticism, spontaneity, and so on. And this will cause enthusiastic denunciations and wild accusations because humans protect sacred values with vigor. Often this is a good thing. But sometimes it is counterproductive and leads to attempts to bury the truth and stifle free scientific inquiry. But these attempts will be in vain, for in an age that values science as much as ours, the truth, whatever it is, will ultimately prevail. And our sacred values will either break or they will adjust.

Human dignity doesn’t require the possession of a 130 IQ, the ability to run a 4.4 40-yard dash, or transcendent beauty. It requires nothing more than being a unique human life. Surely, we can protect and promote this laudable sacred value while also accepting that all humans and all human groups are different, both physically and psychologically.

HUMAN BIODIVERSITY — FREQUENTLY ASKED QUESTIONS

Isn’t true that human variation is unclassifiable and that “race” doesn’t exist?

This is perhaps one of the most divisive and distracting debates about human variation. All serious scholars and researchers agree that human populations vary genetically because of genetic drift and natural selection. They disagree about how best to classify this variation (or whether to classify it at all), and they disagree about whether it has any implications for human psychology. There are roughly three major arguments against the existence of “race”: (1) all variation is gradual not discrete; (2) differences within groups are much more important than differences between groups; and (3) there are many legitimate classifications that contradict each other; therefore, racial classifications are arbitrary. None are terribly persuasive. This article will not cover this debate in detail, but a few comments. (See Noah Carl’s excellent essay at Medium for a longer response.)

First, even if all variation were gradual (or “clinal”), “race” might still be a useful category. Age is completely gradual. However, people make perfectly understandable and scientifically useful classifications such as “child,” “young adult,” “adult,” and “elderly.” These categories are not arbitrary, even if their exact boundaries are. Racial categories would be like these and would be reasonable even in a world of entirely gradual variation (however, variation is not in fact wholly gradual). Second, it is true that there is more variation within human populations than between them, but this doesn’t mean that there isn’t enough variation between human groups to make classification useful. 

And, third, although different scholars have proposed many different racial classification schemes, these are not arbitrary. Scholars generally try to make classifications based on genetic data, phenotypic traits, and ancestry. Proposals that put Icelanders in a category with Japanese people as one group and Han Chinese people with Norwegian people in another group would be rejected by most scientists because they violate the principles of useful classificatory systems.

Why are people who are interested in “human biodiversity”obsessed with race and IQ. Surely that suggests something nefarious?

Not everybody who is interested in human diversity is also interested in IQ; however, it is true that many people who care about human diversity also care about IQ. It’s odd to call that an obsession, though. Scientists study particular things because they are interesting. Many social psychologists, for example, study something called implicit attitudes and there’s no reason to describe this as an obsession. Other researchers study social dominance orientation or political bias. That’s fine. It’s good that scientists are fascinated by different topics. Furthermore, IQ has social significance that is hard to ignore. It predicts a variety of outcomes, and it may help to explain certain disparities in the United States and elsewhere. That makes it important because the best way to address social concerns and problems is to understand the causal mechanisms behind them. Scholars know that there are group differences in intelligence. But, as of now, there is no consensus on the causes.

As noted above, it’s certainly possible that at least some of these differences are caused by genetics. And, if they are, it would be better to know that so that we can talk about it honestly. And, if those differences are not caused by genetics, then it is best to have an open debate about it so the truth can prevail, and we can understand the environmental causes behind the differences. Self-imposed ignorance is rarely a virtue and not only compels ignorance today but also robs the future of knowledge it could have possessed.

Ok, but isn’t that racist? The definition of racism is believing that certain groups are inferior to others. And if IQ differences are partially caused by genes, then is that not contending that some races are genetically inferior to others?

That’s an odd definition of “inferior”. Noam Chomsky is certainly smarter than Al Pacino. That doesn’t make Al Pacino inferior to Noam Chomsky; it makes him less intelligent. Similarly, Noam Chomsky was never remotely as athletic as Lebron James is. That doesn’t mean that Lebron James is “superior” to Noam Chomsky. The same holds for human populations. Let us suppose that the IQ gap between Europeans and Northeast Asians (Asians score a bit higher) is partially caused by genetics. Does that mean that Europeans are inferior to Northeast Asians? Of course not. In fact, one must use a morally dubious definition of “inferior” to suggest otherwise, a definition that suggests that if our neighbors are less intelligent than we are, then they are inferior.

Also, the definition of racism is odd as well. Racism is an irrational hatred or bias against individuals from a particular group simply because they are members of a particular group. If one rejects all Asian applicants for a position because one thinks that they aren’t creative, then that is racist. If one says that Lebron James’s political opinions are irrelevant because “African Americans are not insightful”, then that is racist. But it is not racist to assert that one group, on average, is more athletic or more intelligent than another group. Of course, such claims can be racist and incendiary. If, for example, somebody said, “Europeans are stupid because they can’t compete with Asians on intellectual tasks”, then, at minimum, that would be unnecessarily inflammatory. But observing that “Northeast Asians on average score higher than Europeans on intelligence tests” is no more racist than stating that “African Americans on average are better at basketball than Europeans”. Both are judiciously worded factual assertions. They might be empirically wrong. But they are not racist.

Ok, but what about real racists? Won’t they use this to buttress their hateful worldviews?

Racists will likely use anything they can to support their worldview. Racism is not rational. And it is not motivated by science or empirical observations. However, some of these topics are divisive and therefore require sensitivity. The same applies to discussions about obesity, drug use, attractiveness, or anything else that could be hurtful and divisive. Nevertheless, truth is ultimately more important than transient feelings or concerns. The job of scientists is to pursue the truth, not to promote theories that comfort people.

Also, one of the best ways to help extremists is to silence reasonable discourse about human variation. That will create a vacuum for hateful voices to fill. And they will fill it. Any call to refrain from talking about human variation will only disincentivize contributions from the most moderate and ethically sensitive people. And that will leave the discussion for others.

We can and should denounce hateful racial rhetoric. But we also can and should have reasonable talks about human variation.

But why are HBD people obsessed with immigration and other social policies? Aren’t they using their “research” to promote pernicious social policies? Aren’t they all ethnonationalists?

People who are interested in human variation aren’t necessarily obsessed with immigration or other social policies. Some are interested in such policy discussions, of course, and may use their findings to support or to oppose various social policies. But the science itself is not political. And, in fact, work on human variation can support many different policies, some traditionally liberal and some traditionally conservative — there is no direct line from any scientific is to a political ought. It’s not wrong to use science to support or cast doubt on the wisdom of social policies; but it is wrong to distort science to do so. Therefore, those who are really interested in the science of human variation should categorically denounce those who distort it for political purposes, irrespective of whether those purposes are populist or progressive.

And no, people who study human variation are not all “ethnonationalists”. Many are classical liberals. Some are progressives. Some are centrist. And some are conservative. Some support ethnonationalism, and some support open borders.

Last, it is true that some people who are interested in human variation have pernicious political agendas. But the way to combat such agendas is not to deny the truth; it is to dispute the morality of the agenda itself. Some people who study prejudice, for example, are communists. That doesn’t mean their research is flawed, even if their politics are.

What is the goal of studying human variation is? What do those who promote HBD hope to accomplish?

The goal is to understand human nature and human evolution and to seek answers to fundamental and fascinating questions of who we are and how we came to be. This is not possible without studying human variation. And our scientific climate would be much improved if we learned to talk about such things openly and honestly. Speaking sotto voce about these things or allowing more radical voices to fill the public domain is not a solution. And neither is self-imposed ignorance or the propagation of a noble lie about human uniformity. This may have important consequences for understanding modern society, but we don’t know what those consequences will be. Nevertheless, the first goal should be to understand the world as it is.

Protecting vulnerable populations is laudable. But silencing scientific debates is not. For too long, we’ve allowed a sacred narrative to delimit free scientific inquiry about human variation. The time has come to fulfill the promise of Darwin’s revolutionary scientific paradigm. And that means that we must learn to discuss human variation in psychological traits openly. There is no reason to believe that our society is too immature or depraved to handle the truth. And, in fact, there is good reason to believe that the current regime of silence and suppression is deleterious, allowing the most extreme voices to have a disproportionate impact on public discourse.

Racism is evil, not because all human populations are the same, but because human dignity is not dependent upon sameness. When Thomas Jefferson wrote that “all men are created equal,” he did not mean that they are literally identical. He meant (with language appropriately updated) that all humans are ethically and metaphysically equal.

Ironically, the greatest challenge to this view today comes from progressives who have advocated a panoply of race-based policies as “restitution” for the real and imagined sins of dead Europeans. But those policies are misguided because they begin with an erroneous premise, namely that all human populations would have equal outcomes in absence of racial discrimination. The truth is that human populations, like human individuals, do not have equal talents or traits. And the ardent desire to equalize them will end not in enlightenment, but in tyranny. Those who advocate the candid discussion of HBD believe that honesty about this topic, however temporarily unpleasant, is better than the status quo alternative of blaming whites in perpetuity for all inequities. And ultimately what could be more moderate than the view that we should promote comity and a prudential conversation about reality?

Bo Winegard is the Executive Editor of Aporia

Correction: Fixed a typo; humans began the long exodus from Africa into the Near East 50,000 years ago, not 150,000. Thanks to Razib Khan for spotting this.

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