Thoughts on Human Diversity

Human diversity is complex and controversial, but we know more about our diversity now than at any other point in human history. Charles Murray’s latest book, Human Diversity: The Biology of Gender, Race, and Class, has stirred up op-eds and disagreements in which critics have correctly focused on Murray’s suboptimal description about polygenic scores and the presumed causally between genetic associations with phenotypic traits. The points critics have raised are important and although I largely agree with these criticisms, others have already sufficiently discussed them. Here, instead, I want to focus on my thoughts about the race section of Human Diversity, and Murray’s argument against the idea that race is a social construct.

I have remained intentionally mute on the ongoing scholarly debate of race differences in psychological traits. The debate can be summarized as two oversimplified positions. On one side of the debate, the argument is that race is a social construct in which proponents assert that race differences in skin color or other outwardly visible traits do not correspond to meaningful differences in psychological traits, with IQ being the primary trait of focus. The other side of the debate argues that race is not a social construct, and there are real, partly genetically based differences between races in psychological traits, including IQ.

This debate about the ‘realness’ or ‘biologicalness’ of race intersects with various orthogonal questions: Can the term “race” be used interchangeably with “population”? What evolutionary processes are responsible for any observed differences? If natural selection is responsible for these observed differences, what are the selection pressures that prompted the differences?

Murray, unsurprising to many reading this I would presume, argues against the ‘race is a social construct’ position and states that there is sufficient evidence to reject the proposition that race is a social construct. Human Diversity includes three chapters dedicated to laying out his argument for why race is biologically real. The first chapter focuses on genetic distinctiveness among ancestral populations; the second on evolution since humans left Africa; and the third on population differences in genetic variants associated with psychological traits. This evidence, Murray argues, is supportive of the position that race is a biologically ‘real’ entity.

I disagree.

For a few years now, I have been passively observing the biological race debate unfolding between academics and intellectuals online, wrestling with the arguments and data to come to a confident conclusion about my own position on this topic. Reading Human Diversity has led to the culmination of my position that, yes, race – as has been historically and culturally defined, predominantly by skin color – is more of a social construct than a biological reality. Independent of this conclusion, even if one were to hold the view that race is ‘biological’ Murray’s argument for such a view is simply unconvincing.

The basis for my position that race is more accurately described as a social construct rather than a biological reality rests on two primary points, described in detail below. First, using the terms “race” and “population” interchangeably is inappropriate and inaccurate.  And, second, the extraordinary genetic diversity within continental regions is largely ignored, and currently, too limited to draw convincing conclusions about race differences in psychological traits.

Importantly, however, I do not disagree with the data that Murray presented in these chapters, but I do disagree with the conclusions he draws from them, and I find his presentation of the argument for the position that race is not a social construct inappropriate given the data he uses as support.

I do agree with the claim that human populations differ genetically and for many evolutionary-related reasons. This is an indisputable fact of modern genetic findings that cannot be dismissed. But that human populations differ genetically is not synonymous with the claim that human races differ genetically. Using “population” in place of “race” is a slight I’ve seen used to support the position that races – Black, White, Asian – differ genetically in meaningful ways that contribute to psychology and behavior, which I view as incorrect.

This inappropriate term-switching is used by Murray often in the race chapters of his book. The inconsistency is apparent by looking at the title of the book and comparing it with the chapter titles and propositions in the race section of Human Diversity. To argue against the position that race is a social construct, Murray inappropriately uses data about human populations. Although he defends his term switching by rightfully stating that race has “outlived its usefulness when discussing genetics” (p.135) he then proceeds to inappropriately use the term race throughout the chapters, and uses populations data to support his claim that race is biologically real. (At one point he even refers to other hominid species as “races” of humans.)

That human populations differ genetically, and that Africans, Europeans, and Asians have some broad-level statistical covariation in models is a more appropriately a reflection of human migration patterns over evolutionary history, than meaningful categorical distinctions for understanding psychology. As the number of groups in these statistical models increases, populations begin to split off by regions within these broad continental groups, as Murray shows. Specifying three, seven, or 15 groups, however, is a rather arbitrary decision. Imagine you are an alien visitor with only the genetic data that Murray describes in Chapter 7. Would you pick three groups? Seven? Why? Without pre-existing cultural concepts of race, it is hard to justify an answer that corresponds with socially derived racial groups.

Another problem with these kinds of data is that the data we have from populations within Africa and Asia are incredibly limited relative to that of populations from European. The genetic diversity in African populations is notoriously diverse, yet we have comparably minimal data. As Dr. Adam Rutherford discussed in his book, two Africans are likely to be more genetically distinct from each other than either is to a European. To simply lump all Africans into a single racial group is lazy, misinformed, and more of a reflection of the dearth of data that we have from the continent – an argument that Rutherford articulates elegantly in his book, A Brief History of Everyone Who Ever Lived.

The lack-of-data problem leads me to another criticism of Murray’s argument, which he outlines in Chapter 8: that “evolutionary selection pressure since humans left Africa has been extensive and mostly local”. I have two problems with this line of argumentation. First, what seems to be ignored here is that evolution didn’t stop in African populations when some humans migrated out of Africa – populations in Africa continued to evolve and change, too(!).

The chapter describes evolutionary processes responsible for changes in genetic frequencies between populations, and how migration causes reduction in genetic diversity in the migrating populations. But, the ability of genes to vary (for various evolutionary reasons) across populations does not necessitate that there is, or has been, selection pressures to build adaptations between populations, nor does it make it necessarily more likely. The fact that migrating populations can contribute to genetic differences between Africans (as a group) and Europeans (as a group), must also apply to different (migrating) African populations. The argument is not specific to races; though when Murray frames his argument as ‘evolution post-Africa is extensive’, the evolutionary changes within Africa are ignored.

The second problem I have with this argument is that nearly all the evidence for local adaptations across populations are related to specific physiological process or medical disease traits, not psychological traits. Murray and most other’s arguing for his position describe several population specific traits: sickle cell, altitude adaptations, lactose tolerance, etc. (which don’t even vary consistently across racial lines anyway). The primary difference between these kinds of adaptations and the proposed psychological traits that proponents of Murray’s position argue for, such as IQ or personality, is that the physiological and disease traits have clearly defined selection pressures underlying their evolution and extensive empirical support. Proposals for psychological race differences, however, do not, nor is there strong evidence in support of the claims that I have read. A recent study by doctoral student Kevin Bird tested this idea specifically and shows that IQ differences between Blacks and Whites are not genetically driven nor is there evidence of natural selection operating to produce differences.

Although I think evidence of race differences in psychological traits is unlikely to be (accurately) found in the current research environment, I do not think it is unreasonable to hypothesize and explore questions related to psychological differences between populations (or races). However, it seems to me that the likelihood of finding differences between races is more unlikely than finding differences between populations. Because the variation within races (e.g., ‘blacks’ and ‘whites’ as broad groups) is undoubtedly larger than the variation within specific human populations, the effect sizes for ‘race’ differences would have to be large relative to population differences to be accurately detectable.

Moreover, as I mentioned above, we have an extremely limited amount of genetic data from African populations, relative to populations in Europe and (east) Asia. Thus, current results comparing data from one European population and data from one African population, for example, tells us only about those two specific populations, not about Whites and Blacks as racial groups. More accurate information will be known as the amount of genetic data from non-European populations becomes comparable to that of European populations, and problems of comparing across human populations is resolved.

Murray’s claim that we should move on from the use of race in genetics in favor of population is one I agree with. But that is not consistent with the claim that race is not a social construct. Race, as he describes in Chapter 6, came into the cultural lexicon to categorize people by different skin color and other outward features. What genetics has done is to clearly show that race as skin color or outward features is not a proxy for genetic variation of human populations. Two populations can look the same, but be genetically distant. As Rutherford explains in his book, using ‘black’ skin as a categorical marker hardly makes sense.

What genetics has done for our understanding of race is analogous to what happened in taxonomy with the evolution and genetic revolutions. As described by Dr. Carol Yoon in Naming Nature, taxonomy historically was based on the outward appearance of organisms. Humans have all sorts of culturally useful names for categories of animals, such as fish, birds, and bugs. These categories of animals, like humans, contain enormous diversity within them. Dolphins and trout both swim, bats and magpies both fly, but these outward characteristics from which we group them do not correspond to the biological reality of their relatedness.

This is what has happened with race, in my opinion. As our knowledge of genetics and human diversity has flourished, race – once a seemingly reliable, accurate, and obvious way to categorize human groups – has become a social construct with the acquisition of knowledge. We now know that social categories of race as defined by skin color are not a reliable and accurate way to categorize human groups. So, Murray is right to say that race is no longer an appropriate way to discuss human diversity. He is wrong to conclude from this that race is therefore not a social construct. Race, in my view, is as biologically real as the socially derived, yet meaningful, category “fish”.

9 Replies to “Thoughts on Human Diversity”

  1. A lot of this seems to be a semantic dispute about the word “race,” specifically your claim that using “population” interchangeably with “race” is “inappropriate.”

    It’s my impression that educated people in the past often used “race” more flexibily than you would prefer. For example, they had no trouble talking about things like “the anglo-saxon race” or a “race of pygmies.” It seems that they were trying to get at a concept much like “population” even if they didn’t have the genetic tools we have today.

    Or consider the “races of mankind” sculptures made by Malvina Hoffman for the Field Museum in 1933:

    You can look at the 1933 exhibit booklet, linked from the Wikipedia page, to get some idea what educated people thought about “races” back then. They never would have dreamed of putting aboriginal Australians into the same category as Africans, despite the fact that both groups have “black” skin. And they explicitly recognize the great diversity within Africa. In other words, they weren’t as dumb as Dr. Rutherford seems to think.

    I haven’t read Murray’s book, so I don’t know quite how he uses the term “race,” nor am I an expert on the use of the term through time. Would you agree that this is a semantic dispute about the meaning of the term, or is it more than that?


  2. A race is a sub-population of modern humans that are more similar in some genetic sense to each other than to those in other sub-populations of modern humans. A race is therefore a cluster according to genotype, and the task of identifying races is one of cluster analysis. When cluster analysis is performed, five major clusters emerge, corresponding to races that evolved in Africa, Eurasia, Oceania, East Asia and America. The clusters show near-perfect correspondence with self-reported race.

    The same five population clusters emerged in these five papers:

    Nei and Roychoudhury (1993)

    Bowcock, et al (1994)

    Zhivotovsky, Rosenberg and Feldman (2003)

    Rosenberg et al. (2005)

    Bastos-Rodrigues, Pimenta and Pena (2006)


    1. That’s one definition of ‘race,’ but whether it is a good one is part of what folks have been arguing about, at least since Dobzhansky’s debate with Livingston back in 1962!

      And you only get out those 5 clusters IF you use similar sampling regimes. If you sample more heavily / completely from Africa, you get 2 distinct African clusters at K=5.

      There are better and worse sampling regimes for different purposes, but there is no sense in which there is a “right” sampling regime, or a “correct” number of genomes to get from each region.


  3. I couldn’t help but notice that the paper you quoted (Kevin Bird) doesn’t seem to refute genetic IQ differences between Africans and Europeans, despite its best efforts; in fact it suggests that genetic factors contribute about 20% of the difference between the samples, which is not insignificant considering that we know the huge impacts of childhood and parental nutrition, and childhood illnesses such as malaria, on child cognition. Does this suggest that if there are IQ differences between, say black and white Canadians, while controlling for socio-economic status, this is likely to be far more genetically driven than differences between countries?


    1. “in fact it suggests that genetic factors contribute about 20% of the difference between the samples, which is not insignificant…” I don’t think this is quite right…

      What Kevin’s analysis shows is that differences in allele frequencies associated in genes near markers associated with differences in e.g. I.Q. test-taking performance can’t account for much more than a difference that is 20% as big as the usually cited B/W difference. But first, that’s a maximum, and second, Kevin is quite clear the difference could go in either direction. So it isn’t that “genetic factors contribute about 20% of the difference between the samples” — the genetic factors analyzed can’t account for more than 20%, and IF there are genetic factors that are associated with difference, they might in fact be in the oppose direction of the observed difference (and so wouldn’t help “account” for the observed difference at all!).


      1. I read some of Kevin Bird’s paper. I have not made much sense of the genetic formulas, but one weakness seems to be that he inputs a low value for heritability. To compute the 20% (actually 17%, and he rounded to the nearest 10% himself because of the uncertainty?) between-race genetic effect, he inputs the larger “narrow-sense heritability” as 0.5. Narrow-sense heritability is only the additive effects of alleles, which is always lower than the “broad-sense heritability,” which is both the additive and non-additive effects of alleles. Even broad-sense heritability tends to be below the heritability values estimated by family studies (Devlin et al. 1997 estimated 0.74). Maybe Kevin Bird is correct about the additive effect, but it is of course a limited argument, and it does not say much against the racial hereditiarian position of a strong total genetic effect given the strong correlation.


  4. “As Dr. Adam Rutherford discussed in his book, two Africans are likely to be more genetically distinct from each other than either is to a European. To simply lump all Africans into a single racial group is lazy, misinformed, and more of a reflection of the dearth of data that we have from the continent…”

    I have often seen this argument, but I am not sure how the premise leads to the conclusion. An unspoken premise seems to be that biological races must have equal genetic diversity. But, this has never been a criterion for biological races. In any multiracial species, one race (of the past or present) necessarily has more genetic diversity than all the others combined, given that one race must have been the origin of the other races (which the black African race was). Furthermore, we really can make informative judgments of the phenotypic averages or frequencies of the Sub-Saharan African race, even if they are phenotypically diverse, but on top of that their phenotypic diversity seems to be constrained by their evolutionary history in a somewhat uniform environmental climate (subtropical Africa).


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