This blog post began as a book review solicited by an online periodical called Inference: International Review of Science.
But it turns out to be somewhat disreputable, funded by weird billionaire Peter Thiel, and with noted creationist shill David Berlinski as the third person on its masthead. Apparently the goal is to mix science andpseudoscience so readers become confused and manipulable, and what you end up with is a sort of Fox Science News.
So I withdrew the book review, but kept the book, because it’s a good one and (as I told them) I’m sure Peter Thiel can afford another copy. And here it is.
by Ian Tattersall and Rob DeSalle. Pegasus, 222 pp., USD$27.95.
We are storytelling creatures, the authors explain, before proceeding to tell their own story about where we came from. The origins question is, of course, one of surpassing breadth in our species. Evolve the ability to ask questions, and that particular one emerges near the top of the list: Where did we come from?
The authors are eminently qualified to tell a story that is both authoritative and engaging. Both are curators at the American Museum of Natural History in New York (Tattersall now emeritus). Tattersall’s expertise lies in primate anatomical evolution; DeSalle’s is in molecular evolution. They have written many books separately, and have previously collaborated successfully on the topics of beer, wine, and race.
What does it even mean to be an “accidental” species, anyway? There are several directions in which one could go. First, one could argue that the nucleotide substitutions in the DNA that facilitated bipedalism, canine tooth reduction, cranial expansion, and the like, were all ultimately accidental miscopyings of the DNA in certain late Miocene apes. Indeed the great bulk of DNA changes are in fact neither good nor bad, but neutral, or close enough to neutral that they can be readily carried through the generations within the gene pool. The fact that some accidental DNA changes eventually proved valuable would be ignored here, for this would be a view of human evolution through a lens of the caprice of mutation. Alternatively, one could argue that, unlike many religious views, there is ultimately no reason or telos for our existence; our species is just another accident of nature, not special or central in the history of life, for they all come and go. This was the thesis of Henry Gee’s recent engaging polemic The Accidental Species, but suffers from the fact that our undirected, decentralized, pedestrian development in the universe can’t be proved without standing outside of that universe, which is manifestly impossible, and consequently the point can only be vigorously asserted – even if it may well be true. Yet a third possible aspect of our “accidental” existence might be the stabilization of random variation in our species. Just as there are one-humped (Dromedary) and two-humped (Bactrian) camels, and they both seem to work well as camels, maybe the features that characterize our own species are simply physical variations that work as well as their alternatives. An example might be the syndrome of smallish face, roundish head, and linear body build that seems to have emerged first in Africa about 200,000 years ago and now characterizes our entire species. Indeed when methods have been applied to detect the effects of deterministic natural selection on the evolution of the human form, they have generally failed, suggesting that much of our body or head shape may indeed be “accidental”. A fourth understanding of being “accidental” might be as the result of extraneous events: luckily surviving an asteroid impact or volcanic eruption, and subsequently repopulating the area in one’s own image. Yet a fifth might reside in the classical mathematics by which small gene pools (like those of our ancestors) can deviate from mathematical expectations over the generations, and large gene pools (like ours today) can sustain large amounts of diversity – both of which come with unpredictable consequences.
The story told in The Accidental Homo sapiens is by and large a normative one, and the authors are on sure ground in their discussions of human biological evolution. This is actually not a situation to be taken lightly, for evolution is our particular origin myth, and everybody in science thinks they own a piece of it – unlike, say, boron or electromagnetism. There are, consequently, scientists who borrow and bend human evolution to construct narratives of our origin and nature without a deep knowledge of, well, human evolution. Exhibit A, this book’s antagonists, are the evolutionary psychologists, who came to prominence in the 1990s with glib science bites about human nature. Tattersall and DeSalle argue that the evolutionary psychologists see too much determinism, and not enough accident, in the evolution of our species.
The first two chapters provide a very accessible introduction to statistical quantitative genetics, which is just as difficult to achieve successfully as it sounds. The authors then introduce the possibility of associating quantitative continuous variation in normal human traits to DNA variations, and the limitations of trying to do so. Indeed, given the difficulties in establishing a classical Mendelian basis for a “hard” character like height, the difficulties are compounded in trying to do it for a “soft” character like extroversion or sexual inclination.
The middle of the book recounts the broad features of our ancestry, from the bipedal apes of five or six million years ago, through their descendants a million years ago, who had learned to cut things and burn things, to our (geologically-speaking) recent ancestors, talking and drawing. The evolutionary novelties are biological, technological, and communicative. In the evolution of apes into humans, we can record alterations in the throat and mouth (permitting us to speak), and to the extent that it can be accessed comparatively, in the mind (giving us something to say). We often refer to these properties as symbolic thought, referring to the construction of meaningful imaginary connections between things, as in pointing. In pointing, there is no physical connection between the fingertip and the object, just a metaphorical extension of the fingertip in the mind of the pointer and of anyone with a similarly built brain.
While tools and art were certainly important products of the symbolic capacity, and hugely important in the latterly success of our species, they figure disproportionately in our narratives because they are preserved in the archaeological record. Yet along with tools and art, humans imagined a new social world into existence, which left no material traces yet certainly aided our survival in the material world. This was kinship, and its effects were very far-reaching, if often downplayed.
The final turn of The Accidental Homo sapiens brings us back into the present, trying to explain who we are and how we got here. Was there meaning inherent in the transition from ape to human?
Where the primary antagonists of Henry Gee’s similarly-titled book were those who tried to read purpose or direction into the history of life (No! Our species was accidental!), the targets here are principally modern scholars who see our bodies and minds as finely-tuned machines, having been twiddled and tweaked to precision over the ages by natural selection (No! Our species was accidental!). Hardly anyone doubts today that natural selection has acted upon the human species – the authors are not claiming that our ancestors’ brains grew by accident, but rather by virtue of the persistent long-term survival and proliferation of those bipedal apes that had bigger ones. Their claim is more specifically about how universal and stringent natural selection has been. If natural selection is a sieve, are its pores large or small in any particular case?
When it comes to human behavior, the authors argue that the pores are large. That is to say, once we attained the biological ability to think, act, and speak symbolically, our species was capable of thriving with many different alternatives. This was arguably the “big discovery” of 20th century anthropology: that people all over the world are smart and can survive in places that you can’t, so if you find yourself among them, you had better hope they help you, because you’ll die if they don’t. While this may not sound like much, it was different from the knowledge brought by the early English settlers to America, with often tragic consequences for them.
The modern view, then, is that natural selection worked stringently on the pre-human brain up to a few hundred thousand years ago, when the adaptive value of the collective intelligence of cultures began to overwhelm the adaptive value of individual minds, and classical natural selection accordingly diminished. Nearly all of what people do consequently has negligible relative survival or reproductive value and is not the result of natural selection, but of historical contingency, or accident. That is as well the view of Tattersall and DeSalle, but not of their antagonists, the sociobiologists and evolutionary psychologists. These latter scholars generally assume that natural selection acts on individual human behaviors, and consequently they generate biologically-based narratives for each one. By so promiscuously invoking natural selection, which is a genetic process, these scholars imagine the genes to be doing an awful lot of heavy lifting; but since they are mostly drawn from ethology and psychology, not genetics, it generally doesn’t bother them. Tattersall and DeSalle are bothered, however, and argue against analytically atomizing human behaviors, against ascribing biological bases to the behaviors, and against invoking natural selection wantonly as their cause. That obviously leaves the sociobiologists and evolutionary psychologists in a limbo of bad evolutionary theory.
The criticism is welcome, as the abuse of evolution has a long and embarrassing history. The central problem that Tattersall and DeSalle highlight is the difficulty in reconciling binary Mendelian alleles (wrinkled/round, green/yellow, tall/short) to the quantitative and developmentally sensitive human organism, much less to its context-specific behaviors.
This problem has existed since the dawn of Mendelian genetics. In the early 20th century, America’s leading geneticists generally adhered to the proposition that people came in two Mendelian flavors, smart and “feebleminded”. Their arguments helped pass legislation to restrict the immigration of Italians and Jews into the US (1924) and to sterilize the poor involuntarily (1927), before the Germans even got the idea. Today’s abusers of Mendel are only slightly less crude, with genes “for” homosexuality, schizophrenia, aggression, or religiosity regularly touted, although with remarkably short scientific shelf-lives.
Tattersall and DeSalle rather favor a model in which genes could not do that much work, because they do not “code for traits” but set a range of possibilities, often quite broad, that can be expressed in various ways, dependent upon various factors. The pedagogical model we most often rely on imagines the phenotype (i.e, detectable physiology) to be readily predictable from the genotype (i.e, genetic status). And sometimes that is true. If you have the alleles for cystic fibrosis, you will generally express the disease. If you don’t, you generally won’t. If you have the alleles for lactate dehydrogenase A, you will generally express the enzyme. If you don’t, you generally won’t. But aside from pathologies and biochemicals, one hardly ever finds binary patterns. Rather, we find genes expressed in diverse ways (pleiotropy), genes affecting the expression of other genes (epistasis), traits that may not appear in spite of the genes (penetrance), and context-dependent gene expression (reaction norms). This is an immensely valuable presentation of the way genetics actually functions in human affairs, in contrast to the simplistic models underpinning the evolutionary psychology literature.
Where the authors come up just a bit shy, I think, is when they try to explain why reductive, hereditarian ideas about behavior and intelligence persist in the scholarly literature after all this time. They present a few possibilities : “the human mind … seems naturally drawn to reductionist explanations” (p. 45); “scientists may sometimes be uncomfortable with uncertainty, and … genetic and genomic hypotheses promise clear-cut cause-and-effect explanations (pp.72-72); and “when humans are told that something is very difficult or even impossible to do, the immediately attempt it anyway.” ( p. 73).
There is, however, something else at work, which scientists are generally loath to confront, for it exposes an embarrassing side of the practice of science. The sad fact is that arguments about genetic determinism take place upon a biopolitical and moral ground as well as upon an empirical scientific one. The same philanthropies and demagogues that promote hereditarianism also promote scientific racism (i.e., the recruitment of authority of science in support of the evil politics of racism). The hereditarian psychologists Arthur Jensen and Thomas Bouchard, the racist psychologist Philippe Rushton, and the hereditarian political scientist Charles Murray are all linked through networks of right-wing interests. And a lot of money has been spent to get wacko ideas into the scientific mainstream, with distressing levels of success.
Classically, the argument looked like this: Blacks are inherently dumber than whites, therefore they do not deserve equal rights. The updated, subtler version goes: Low-IQ people are inherently dumber than high-IQ people; IQ determines social and political status; therefore social programs intended to ameliorate extreme social stratification are doomed to failure, and federal funding should be directed elsewhere.
This is not a scientific problem, but a problem for science, and one that scientists are not trained to resolve – the problem of evil. The problem is social, political, and moral, and requires the constant vigilance of the scientific community to avoid sullying the good names of Darwin and Mendel.
After challenging the reification of genes, the attribution of human behaviors to them, and the blithe assumption by the evolutionary psychologists that acts are adaptive and governed by natural selection, Tattersall and DeSalle’s narrative winds down by engaging with our uniqueness as a species. If, as the authors tell us, “no creature in the world today is more unlike its ancestor of two or three million years ago than we are,” then does that fact come with scientific implications? They toy with the idea of such a newly-arisen evolutionary gulf implying that our species alone ought to be placed in a new Subkingdom Psychozoa, as the biologists Julian Huxley and Bernhard Rensch suggested many years ago. But they quickly reject it, because modern scientific sensibilities value phylogeny (how closely related we are to the apes) more highly than divergence (how different from them we have become). I wish they had pursued this point a bit further, because it is ultimately an arbitrary decision, which is nevertheless imbued with scientific meaning in spite of itself being largely “accidental”.
The Accidental Homo sapiens is a short, straightforward book that tells a very scientifically validated story of who we are and how we got here. There are various classes of data and evidence to work with. But making up imaginary genes as part of a narrative of human origins doesn’t do much credit to the scientific endeavor. The authors strongly discourage it, and so do I.
 Henry Gee, The Accidental Species: Misunderstandings of Human Evolution (Chicago: University of Chicago Press, 2014).
 Lauren Schroeder and Rebecca Rogers Ackermann, "Evolutionary processes shaping diversity across the Homo lineage." Journal of Human Evolution 111(2017):1-17.
 John P. Jackson and David J Depew, Darwinism, Democracy, and Race: American Anthropology and Evolutionary Biology in the Twentieth Century. (New York: Taylor & Francis, 2017).
 William H. Tucker, The Funding of Scientific Racism: Wickliffe Draper and the Pioneer Fund. (Urbana, IL: University of Illinois Press, 2002).
 Angela Saini, Superior: The Return of Race Science (Boston, MA: Beacon Press, 2019).
 Carleton Putnam, Race and Reason (Washington, D. C.: Public Affairs Press, 1961.)
 Richard Herrnstein and Charles Murray, The Bell Curve (New York: Free Press, 1994).
 Julian S. Huxley, "Evolution, biological and cultural." Yearbook of Anthropology [Continued as Current Anthropology] 0:2-25 (1955). https://www.journals.uchicago.edu/doi/abs/10.1086/yearanth.0.3031134