Critical Hominin Theory

[Note: Both reviewers recommended publication of the following essay for Paleoanthropology, but it has not yet been accepted. If you like it and want to cite it, go ahead and cite this page. I'll let you know if it ever gets officially published.]

Introduction: Physical anthropology as pseudo-taxonomy

At one time, the field of physical anthropology was occupied primarily with establishing the number and natures of the elementary natural units of the human species. Radical biologists, like Ernst Haeckel (1868) , W. C. Osman Hill (1940) and Reginald R. Ruggles Gates (1944) even held the different varieties of living peoples to be themselves species, rejecting the familiar interbreeding criterion. Nevertheless, once that question was resolved to everyone’s satisfaction, in the early 1960s, (e.g., Barnicot 1963), the question still remained about how to understand the elementary units of the human species taxonomically below the species level. 

In Nature, Campbell (1962) formally identified H. sapiens sapiens, H. sapiens afer, H. sapiens asiaticus, H. sapiens americanus, H. sapiens australasicus, and H. sapiens neptunianus. Concurrently, based on serological genetic considerations, Boyd (1963) proposed thirteen human “races,” clustered into seven “groups” in Science.  Garn (1961) identified nine “geographical races” and 32 “local races”. Coon (1962) identified five subspecies of living Homo sapiens (ignoring the additional nonsense about their having evolved in parallel from five subspecies of Homo erectus, and its possible bearing on school integration), namely: Caucasoids, Mongoloids, Negroids, Capoids, and Australoids.

In the intervening decades, we stopped thinking about and teaching about human variation that way in physical anthropology.  We have learned to talk about human variation without formal biological taxonomy. The actual empirical biological structure of our species is “regarded as constituting a widespread network of more or less interrelated, ecologically adapted and functional entities” (Weiner 1957: 80), or in contemporary language, a “structured metapopulation” that defies taxonomic precision.  The groups that compose our species are created for particular purposes, and while they may correlate with some biological patterns, they do not represent natural divisions, but political identities. Classifying our species as Linnaeus did turned out to be a square peg – round hole problem (Livingstone 1962). Race can thus be modeled on the classic anthropological example of African witchcraft (Evans-Pritchard 1937; Fields and Fields 2012), which structures people’s lives in spite of not having any material, naturalistic existence.

Indeed, partly as a result of the historical baggage associated with treating the human species in such a pseudo-taxonomic fashion, we terminated physical anthropology altogether and rebranded ourselves formally as biological anthropology. Yet even as biological anthropology, we retain the urge to try and make sense of the ostensible lineages in our ancestry taxonomically (e.g., Wood and Boyle, 2016; Reed et al., 2023), a daunting task that even Linnaeus himself never faced back in the 18^th century.

A popular science bestseller, Harari’s (2014) Sapiens, told readers on its back cover that “[o]ne hundred thousand years ago, at least six different species of humans inhabited Earth”. That, of course, might indeed be true. What are the six species he identified 100,000 years ago? One, Homo sapiens, modern people. Fair enough, if a bit on the robust side. Two, Homo neanderthalensis. Indeed, according to the best genetic data thirty years ago (Krings et al. 1997); but now the geneticists say I may have 2% Neanderthal DNA, which presumably changes the status of Neanderthals, or the status of species, or both (Harvati and Ackermann 2022; Weasel 2022). Three, Homo denisova. Yet even the geneticists, who are the only people to whom it is visible, say this is a genomic subgroup of Neanderthals (Meyer et al., 2012) – who, as just noted, may not even be their own species in the first place. Four, Homo erectus. That is largely uncontroversial as a taxon; but not at 100,000 years ago, unless perhaps we regard species #6 as H. erectus. Five, Homo floresiensis. Clearly, the mysterious and isolated H. floresiensis was something (Madison 2023). And six, Homo soloensis, named for a different set of Indonesian fossils than H. floresiensis, which are generally regarded as archaic H. sapiens (Swisher et al., 1996) on account of their anatomical continuity with both H. erectus and H. sapiens.

All of a sudden, we are down from “at least six different species” to humans, the hobbit, and possibly Neanderthals. This is not to single out Harari for criticism, but rather to note that biological anthropologists know that all of these species are vexatious at best (e.g., Athreya and Hopkins 2021; Bae et al., 2023), while outside of biological anthropology, the nuanced winks that generally accompany these taxa tend to get lost.

The problem is not a new one. Reviewing mammalian systematics in 1945, G. G. Simpson was frustrated by the difference he encountered between paleontological and paleoanthropological taxonomy. Since human are mammals, it stands to reason that an expert on mammalian species should be able to make sense of extinct hominin[1] species. Like any other biological taxonomic enterprise, there is a proper taxonomic scheme, reflecting a proper understanding of the fossil species in that particular evolutionary lineage. It’s simply a matter of finding it. Some people see too few species (lumpers), and some people see too many species (splitters), while a competent paleontologist should produce results that are as Goldilocks found the baby bear’s porridge: just right.

The problem, however, is not simply that everybody fancies themselves to be the baby bear; but rather, lies more fundamentally in the assumption that the elementary units in paleoanthropology and the elementary units of paleontology are equivalent. I think it is time to call that assumption into question. The units of paleontology, and of biology more generally, are different from the units of paleoanthropology, in that the latter are units in a story of our ancestors, and the ancestors are invariably sacred.

What are primate species?

A species, like a culture or a gene, is infamously difficult to define precisely and satisfactorily. Species appear to be units of nature of some sort, but different kinds of units than species among plants or bacteria (Godfrey and Marks 1991; Barraclough 2019). Nevertheless, for multicellular animals at least, it appears to be an elemental unit of ecology, as a cell is an elemental unit of physiology, a genotype is an elemental unit of a population genetics, and an organism is an elemental unit of society. If we restrict ourselves just to the more familiar mammalian and primate species, we can ideally identify several properties possessed by a species: (1) it is composed of organisms related to one another as either potential mates or competitors for mates, thus bounded by the limits of a gene pool; (2) it constructs and is adapted to a niche, filling a role in a dynamic ecosystem; (3) it has a locus in space and a duration in time as an evolutionary lineage; and (4) it can replicate, making more species, each slightly different from itself. Different definitions of species, from Buffon (1753; Farber 1973) through Mayr (1942) and beyond, highlight one or another of these features.[2]

A more recently-appreciated feature of species is that they are also units of conservation legislation, and thus partly cultural as well. That is why the number of extant primate species has risen so dramatically in recent decades, from about 170 in the mid-1980s (Richard 1985) to over 500 today (Strier 2022). It is not simply that the number of species is being taxonomically inflated, and is thus less accurate than it used to be (Rosenberger 2012); or that new species are finally being recognized, and their number is thus more accurate than it used to be (Groves 2014). In a sense, comparing the number of living primate species 35 years ago and today is simply unfair, because they are actually tabulating different things than they used to.

 However entropic the universe of extant primate species seems to have become, it is disconnected from extinct primate species, which are of course unaffected by conservation legislation. They nevertheless have their own issues, and their status is constantly being negotiated by the community of primate paleontologists. Perhaps unsurprisingly, the closer we get to ourselves, the more complex things seem to become (Kimbel and Martin, 1993).

Hominin species seem just as vexed today as they did to Simpson back in 1945. His explanation was that the people doing the paleoanthropology were generally coming from medical anatomy, and simply didn’t understand taxonomy well enough: “much of the work on primates has been done by students who had no experience in taxonomy and who were completely incompetent to enter this field, however competent they may have been in other respects” (Simpson 1945:181). In particular, he noted, “Dart's placing of Australopithecus in a family ‘Homo-simiadae’ (1925) only served to exemplify the total ignorance of zoology so common among the special students of these higher primates (although, of course, Dart's work is excellent in his own field)” (Simpson 1945:188).

The ontology of hominin species

The underlying presupposition is that hominin biological history is composed of zoological units that are equivalent to species, however species may be defined biologically. Thus, Homo naledi, Homo longi, Homo heidelbergensis, Homo luzonensis, etc., either are or are not distinct phylogenetic lineages, and only a proper taxonomy will resolve and describe it.
Suppose, however, that there are no recoverable biological species in the history of our lineage, perhaps because much of that history is occupied biologically by a structured meta-population rather than by distinct species (Pääbo 2015; Scerri et al. 2019). Perhaps because there is more at stake in identifying our ancestors than there is in identifying the ancestors of other species. Perhaps because the names themselves represent not so much biological ancestors, as anthropological ancestors.

What do I mean by an anthropological ancestor? I mean the subject of a sacred narrative about our past, a story intended to explain who we are and how we came to be here. The diverse manners by which peoples construct relations of (horizontal) kinship and (vertical) ancestry was among the earliest discoveries of anthropology (Morgan 1871; Franklin & McKinnon 2001). And while we have talked for decades about looking at science as a culture (Snow 1959), we are only recently actually getting around to doing it (Franklin 1995). I want to suggest that the reason that hominin taxonomy is, and has always been, so vexed, is because its elements are not biological species. The species that compose our own lineage are mythic ancestors, which are intended to resemble biological species. But they are actually elements in a story, the bricolage (Lévi-Strauss 1962) out of which scientific narratives of our origins (Landau 1985) are constructed.

In one story, the actor in a creation story might be Mother Corn Spirit. In another, it might be Homo luzonensis. In still another, it might be Homo soloensis. And they might have precisely the same ontological status: as nonexistent naturalistic entities in human ancestry. As some other kind of entities, namely as characters in an origin narrative, they may have a very different kind of existence.
The persistent confusion over hominin taxonomy is a result of misunderstanding the nature and existence of hominin species. It is not that there is a correct taxonomic interpretation of the fossils, which will reveal itself under the proper analytic technique. It’s that (1) this taxonomic practice is different from other ostensibly zoological taxonomic practices, by virtue of being reflexive; (2) the origin of this difference lies in the fact that it is naming and describing our own ancestors, and (3) ancestors are invariably sacred (in the broad anthropological sense of “special”, rather than in the narrower sense of “holy,” although the ancestors may of course sometimes be that too; Zerubavel 2012).

Figure 1: A notoriously sacred ancestor,
Eoanthropus dawsoni, or Piltdown Man.

Anthropologically speaking, hominin species are sacred ancestors. In some cases, this is more obvious than others. The role of Eoanthropus dawsoni as a sacred British ancestor (Figure 1), which effectively precluded its exposure as a hoax for decades, is well-known (Weiner 1955). Another notable example is Sinanthropus pekinensis. We often retell the story of the loss of the Peking Man fossils on Pearl Harbor Day. They were being transported for safe keeping to the naval base in Hawaii to protect them from the Japanese, who were very interested in taking control of the fossils (Roberts et al. 2021). We never tell a parallel story in Europe: After all, there were hominin fossils scattered around Europe in 1941, but they didn’t require special protection from the Germans. Why did Peking Man require protection from the Japanese? Presumably, because the fossils were regarded as ancestors of the Chinese (Sautman 2001; Schmalzer 2008), and thus possessed symbolic power and value to East Asians, which was quite different from the cultural meanings of European fossils.

And it wasn’t even Homo erectus at the time, but Sinanthropus pekinensis. That is what all of these names represent: not elements of biological history, but elements of stories about biological history. They are attempts to create formal biological characters and distinctive elements in order to convey a story of human origins, where there are, in fact, no such formal biological distinctions in nature.  This situation is familiar from the neontological end of physical anthropology, in the form of two centuries of misguided racial classification. I am suggesting that the problem with paleoanthropological taxonomy today is the same problem with racial taxonomy decades ago: namely, a fundamental confusion of categories, mistaking units of symbolic culture for units of biological nature.

Figure 2: An ancestor (STS-5 or Mrs. Ples)
on a postage stamp 

Some famous fossil ancestors have appeared on national postage stamps (Figure 2), an unusual location for scientific data. My point is that studying and narrating one’s own ancestry is a culturally powerful activity. The elements of a scientific story of our ancestors are species, and those species are not like other species, by virtue of being our ancestors (Walker et al., 2021). We are humans studying human ancestors; the reflexivity is built into the system. In order to break out of the loop (Huxley 1863:69), we can pretend to be space aliens (“scientific Saturnians, if you will”), but that is hardly a scientific solution to any problem.

We no longer teach the pattern of extant human variation as being taxonomically structured, because we have come to realize that the taxonomies of race did not in fact represent what they purported to: the existence of a fairly small number of fairly discrete and fairly natural clusters of people. By shifting the ontological status of race from the biological to the cultural (obviously, sometimes correlated with a bit of biology), race has become no longer a subject of formal biological taxonomy. Consequently, whether the International Code of Zoological Nomenclature recognizes Homo sapiens afer as a valid subspecies is irrelevant, for it isn’t actually a biological thing. It is simply one of the many cultural ways that humans form politically salient groups, and consequently one of the identities that are available for people to adopt in a particular time and place. 

Similar reasoning can be applied to human ancestry. We may begin to regard Homo heidelbergensis, for example, as ontologically equivalent to Homo sapiens asiaticus. That is to say, as an attempt to apply scientific taxonomic rigor where it is inapplicable, by naming something and thus willing it into existence. This is the fallacy of reification, or misplaced concreteness. There is no Homo sapiens asiaticus, although we can certainly discuss the peoples of East Asia, their gene pools, and their adaptations. We do not recognize Linnaean subspecies taxa as describing our species at present. Are the Linnaean species taxa that ostensibly describe our ancestry any realer? Or are they primarily serving to conceal the actual structure of human prehistoric biology? It is, after all, at least conceivable that the human lineage was more like a structured metapopulation than like a clade, all the way down. If that were true, then gene flow would presumably be occurring, which becomes a mechanism for the horizontal transmission of derived characters. If derived characters are transmitted horizontally by gene flow, rather than vertically by common ancestry, that would render any ostensible phylogenetic analyses untenable; in which case the goal of establishing a proper taxonomy and phylogeny for recent hominin fossils (e.g., Bae et al., 2023) would be impossible.

Conclusion

Figure 3: Five official kinds of living people, from 1911 

            We talk today about a species Homo sapiens, and even about a subspecies, Homo sapiens sapiens, without further formal taxonomic structure, although with real and studiable patterns of biological diversity below that level. But instead of characterizing Homo sapiens europaeus as if it were a naturalistic taxon, today we ask instead why scientists thought it existed as such for two or three centuries when it actually doesn’t (Figure 3). Instead of asking how many and what the human races are, we ask how and why they get made, and what work they do. We may look similarly at the question in paleoanthropology of how hominin species get made and manipulated – without necessarily assuming that hominin species are biological things, because that is what we think our prehistory is supposed be composed of. It may be that the quest for a proper and correct taxonomy of hominin species is itself a vain one.

The 18th century Linnaean tree of classification does not map perfectly on to the 19th century Darwinian tree of phylogeny. Why not? Because adaptive Darwinian divergence creates paraphyletic Linnaean categories – such as invertebrates (minus vertebrates), fish (minus tetrapods), reptiles (minus birds), monkeys (minus hominoids), and apes (minus humans). Consequently, 21st century cladistic classifications often have weird components, as they attempt to make all recognized taxa monophyletic (Withgott, 2000). Nevertheless, even Linnaeus was not faced with trying to incorporate extinct taxa into his work; he didn’t even believe in extinction. Moreover, Linnaeus did not know about macro-and micro-evolution when he formulated his system, and the distinction has vexed systematists ever since, since speciation is a process and not an event, and thus reproductive isolation (if that is your criterion of species) is often incomplete (Dobzhansky, 1937).

The recent paper by Meneganzin and Bernardi (2023) about Neanderthal specieshood underscores the problem. With imprecise definitions of what “human,” “Neanderthal,” and “species” mean, the Linnaean system simply breaks down here. They may well be right: Neanderthals may indeed be a “good” species, assuming that species actually mean something real and biological in this context. But I would suggest that Neanderthals are neither a “good” species nor a “bad” species; the imposition of biological species labels where the species are at best biologically ambiguous is the problem. That would be a problem anywhere on the “tree” of life; but Neanderthals have the added burden of sitting on the boundary between the human and the nonhuman, which is about as singularly symbolically charged as any place you can imagine. 

Perhaps hominin species do more harm than good at present, when it comes to understanding the bio-historical processes and patterns that got us here. Perhaps hominin species are examples of scientific pareidolia: projecting patterns like faces onto objects like clouds and tortillas. If you really want them to be there, you can always find them. The problem lies in convincing everyone else that they are there.

References

Athreya, S., & Hopkins, A. 2021. Conceptual issues in hominin taxonomy: Homo heidelbergensis and an ethnobiological reframing of species. Yearbook of Physical Anthropology, 175(Suppl. 72), 4–26.

Bae, C.J., Aiello, L.C., Hawks, J., et al. 2023. Moving away from “the Muddle in the Middle” toward solving the Chibanian puzzle. Evolutionary Anthropology (in press). doi:10.1002/evan.22011

Barraclough, T. G. 2019. The Evolutionary Biology of Species. New York: Oxford University Press.

Boyd, W. C. 1963. Genetics and the human race. Science, 140:1057-1065.

Buffon, Count de. 1753. l'Asne. In: Histoire Naturelle, Générale et Particuliére, Vol. IV. Paris: Imprimerie Royale, pp. 337-436.

Campbell, B. 1962. The systematics of man. Nature, 194:225-232.

Coon, C. S. 1962. The Origin of Races. New York: Knopf.

Dobzhansky, T. 1937. Genetics and the Origin of Species. New York: Columbia University Press.

Evans-Pritchard, E. E. 1937. Witchcraft, Oracles, and Magic Among the Azande. Oxford: Oxford University Press.

Farber, P. L. 1972. Buffon and the concept of species. Journal of the History of Biology, 5: 259-284.

Fields, B., and Fields, K. 2012. Racecraft: The Soul of Inequality in American Life. New York: Verso.

Franklin, S. 1995. Science as culture, cultures of science. Annual Review of Anthropology, 24: 163-184.

Franklin, S., & McKinnon, S., eds. 2001. Relative Values: Reconfiguring Kinship Studies. Durham, NC: Duke University Press.

Garn, S. 1962. Races. Springfield, IL: Charles C. Thomas.

Godfrey, L., & Marks, J. 1991. The nature and origins of primate species. Yearbook of Physical Anthropology, 34: 39-68.

Groves, C. P. 2014. Primate taxonomy: Inflation or real? Annual Review of Anthropology, 43: 27-36.

Harari, Y. N. 2014. Sapiens: A Brief History of Humankind. New York: Random House.

Harvati, K., & Ackermann, R. R. 2022. Merging morphological and genetic evidence to assess hybridization in Western Eurasian late Pleistocene hominins. Nature Ecology and Evolution, 6: 1573–1585.

Huxley, T. 1863. Man's Place in Nature. London: Williams and Norgate.

Kimbel, W. H., & Martin, L. B., eds. 1993. Species, Species Concepts and Primate Evolution. New York: Plenum.

Krings, M., Stone, A., Schmitz, R. W., Krainitzki, H., Stoneking, M., & Pääbo, S. 1997. Neandertal DNA sequences and the origin of modern humans. Cell, 90:19-30.

Landau, M. 1991. Narratives of Human Evolution. New Haven: Yale University Press.

Lévi-Strauss, C. 1962. The Savage Mind. Chicago: University of Chicago Press.

Livingstone, F. B. 1962. On the non-existence of human races. Current Anthropology, 3, 279-281.

Madison, P. 2023. Tug-of-War: Bones and stones as scientific objects in postcolonial Indonesia. Isis, 114:77-98.

Mayr, E. 1942. Systematics and the Origin of Species. New York: Columbia University Press.

Meneganzin, A., and Bernardi, M. 2023. "Were Neanderthals and Homo sapiens ‘good species’?" Quaternary Science Reviews 303: 107975. https://doi.org/https://doi.org/10.1016/j.quascirev.2023.107975.

Meyer, M., Kircher, M., Gansauge, M.-T., Li, H., Racimo, F., Mallick, S., . . . Pääbo, S. 2012. A high-coverage genome sequence from an archaic Denisovan individual. Science, 338: 22-226.

Morgan, L. H. 1871. Systems of Consanguinity and Affinity of the Human Family. Washington, DC: Smithsonian Contributions to Knowledge, Volume 17.

Osman Hill, W. C. 1940. Classification of Hominidae. Nature, 146: 402-403.

Pääbo, S. 2015. The diverse origins of the human gene pool. Nature Reviews Genetics, 16(6), 313-314.

Reed, D. N., Raney, E., Johnson, J., Jackson, H., Virabalin, N., & Mbonu, N. 2023. Hominin nomenclature and the importance of information systems for managing complexity in paleoanthropology. Journal of Human Evolution, 175, 103308.

Richard, A. F. 1985. Primates in Nature. San Francisco: W. H. Freeman.

Roberts, M. F., DeVisser, E. M., & Marrant, J. P. 2021. Treacherous evidence: Archival documents and the search for Peking Man. PaleoAnthropology, 1:98−119.

Rosenberger, A. L. 2012. New World Monkey nightmares: Science, art, use, and abuse (?) in platyrrhine taxonomic nomenclature. American Journal of Primatology, 74(8), 692-695.

Scerri, E. M. L., Chikhi, L., & Thomas, M. G. 2019. Beyond multiregional and simple out-of-Africa models of human evolution. Nature Ecology & Evolution, 3:1370-1372.

Schmalzer, S. 2008. The People's Peking Man: Popular Science and Human Identity in Twentieth-Century China. Chicago: University of Chicago Press.

Simpson, G. G. 1945. The principles of classification and a classification of mammals.  Bulletin of the American Museum of Natural History, 85: 1-349.

Snow, C. P. 1959. The Two Cultures and the Scientific Revolution. London: Cambridge University Press.

Strier, K. B. 2021. Primate Behavioral Ecology, 6^th ed. New York: Routledge.

Swisher, C. C., Rink, W. J., Antón, S. C., Schwarcz, H. P., Curtis, G. H., & Suprijo, A. (1996). Latest Homo erectus of Java: Potential Contemporaneity with Homo sapiens in Southeast Asia. Science, 274: 1870-1874.

Walker, J., Clinnick, D., and White, M. 2021. "We are not alone: William King and the naming of the Neanderthals." American Anthropologist 123 (4): 805-818. https://doi.org/https://doi.org/10.1111/aman.13654.

Weasel, L. 2022. "How Neanderthals became white: The introgression of race into contemporary human evolutionary genetics." The American Naturalist 200 (1): 129-139. https://doi.org/https://doi.org/10.1086/720130.

Weiner, J. S. 1955. The Piltdown Forgery. London: Oxford University Press.

Weiner, J. S. 1957. Physical anthropology: An appraisal. American Scientist, 45: 79-87.

Withgott, J. 2000. "Is it “So Long, Linnaeus”?" BioScience 50: 646-651.

Wood, B., &. Boyle, E. 2016. Hominin taxic diversity: Fact or fantasy? American Journal of Physical Anthropology, 159(S61): 37-78.

Zerubavel, E. 2012. Ancestors and Relatives: Genealogy, Identity, and Community. New York: Oxford University Press.

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[1] Although I reject the two premises that led to the adoption of “hominin” (only naming clades, and privileging our genetic intimacy with the apes over our ecological difference from them), I use the term for its hipness.

[2] I regard a species to be a group of organisms composed of potential mates and competitors for mates, and representing a temporarily stable state in a biopolitical field of evolution, ecological relations, capitalism, conservation science, and governmental action.

Necessity and Chance

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.

The Accidental Homo sapiens: Genetics Behavior, and Free Will 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,[1] 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”.[2]  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 20^th 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 20^th 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.[3] 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).[4] 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.[5]

Classically, the argument looked like this: Blacks are inherently dumber than whites, therefore they do not deserve equal rights.[6]  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.[7]

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[8] 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.

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[1] Henry Gee, The Accidental Species: Misunderstandings of Human Evolution (Chicago: University of Chicago Press, 2014).

[2] Lauren Schroeder and Rebecca Rogers Ackermann, "Evolutionary processes shaping diversity across the Homo lineage." Journal of Human Evolution 111(2017):1-17.

[3] 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).

[4] William H. Tucker, The Funding of Scientific Racism: Wickliffe Draper and the Pioneer Fund. (Urbana, IL: University of Illinois Press, 2002).

[5] Angela Saini, Superior: The Return of Race Science (Boston, MA: Beacon Press, 2019).

[6] Carleton Putnam, Race and Reason (Washington, D. C.: Public Affairs Press, 1961.)

[7] Richard Herrnstein and Charles Murray, The Bell Curve (New York: Free Press, 1994).

[8] 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

Homo naledi shows how biological anthropology is not biology, and can't be, and shouldn't be

            I once read somewhere that the most interesting thing about human evolution is how everbody thinks they understand it.

            I suspect it's because everyone thinks they own a piece of it.  It's the story of where we came from, after all!  And not just any story of where we came from - it's the authoritative, scientific story.

            The authoritative origin stories are not like other stories.  They are value-laden in ways that other scientific stories are not.  Archaeology is routinely used in the service of nationalism, for example.  Rather moreso, at least, than fruitfly genetics is, so a fruitfly geneticist, or a general biologist, might be excused for not being an appropriately critical reader of the literature on human evolution or diversity, where there is rather more at stake.  It is a different and unfamiliar literature to them, and consequently requires some additional intellectual effort for a trained biologist to make sense of. Some don't bother.

            Now, there have been some very insightful contributions to the scholarly literature on human variation and evolution from biologists, even fruitfly geneticists, over the years.  I can think of three off the top of my head.

1935

2011

1962

Julian Huxley collaborated with the Cambridge social anthropologist Alfred Cort Haddon for this important early critique  of race, We Europeans. Rob DeSalle collaborated with biological anthropologist Ian Tattersall on their recent book, Race? Debunking a Scientific Myth.  And Doby was a friend and collaborator of several anthropologists, including Sherwood Washburn, Ashley Montagu, and Margaret Mead.

            In science, our answers to the question of where we came from are stories that center around a descent from the apes.  And our characters are already there for us: The human lineage is composed of species, just like the units of paleontology and ecology. A recent ethnographic paper by Eben Kirksey begins, "Taxonomists, who describe new species, are acutely aware of how political, economic, and ecological forces bring new forms of life into being." That is probably true, but I think generally not in the first person. That is to say, the taxonomist working with "political, economic, and ecological forces" is usually somebody else; I'm the taxonomist who is uncovering raw nature.

            Back in 1945, paleontologist George Gaylord Simpson was reviewing the literature on  mammal taxonomy, but when he got to humans, he found it impenetrable.  He had an idea why it was so impenetrable to him, as well: “A major reason for this confusion is that much of the work on primates has been done by students who had no experience in taxonomy and who were completely incompetent to enter this field, however competent they may have been in other respects”.[1] 

GGS in 1983

            Granted that many of the workers in the field may have been trained principally in medical anatomy rather than in evolutionary paleontology, Simpson thought it was reasonable to expect that an expert on  the species of other kinds of mammals should be able to translate freely to the literature on human evolution, because the units ought to be the same.  But he misunderstood the species in our own lineage, for these taxonomic entities are not like the taxa of biology.  Simpson hoped to study his ancestors dispassionately and rationally, as perhaps Vulcans  contemplate their ancestors.[2] But a purely rational and logical Vulcan approach to ancestry involves not dividing people into relatives and non-relatives, for they acknowledge that rationally and logically, everyone is related. They also do not consider ancestry beyond the twelfth generation (approximately 300 earth-years, because in the 12^th generation, every sexually-reproducing organism had 4096 ancestors, which is rather a lot to track; and each contributed less than 1/40 of 1% of the genome, so none of them on average is particularly genetically significant).  But we aren’t Vulcans, we are Earthlings, and we treat our kinship and descent in all kinds of meaningfully irrational (but nevertheless coherent and logical!) ways, even in science.

            The classification of our ancestors is still vexed.  Sure, scientists acknowledge some of our colleagues to be “lumpers” or “splitters” – interpreting anatomical diversity among the fossils to be the result of age, sex, pathology, deformation, and microevolution,  thus “lumping” the fossils into few species; or conversely “splitting” them into many species by interpreting the anatomical diversity taxonomically.  But there is something else going on here.  This is participation in the construction of an authoritative story of our ancestry.  There is simply more at stake than in the narrative of clam or deer ancestry. The units here, the species, are not comparable to the species the zoologist is familiar with, for these are not units of ecological genetics, but units of story.

[from a forthcoming paper in Philosophy, Theology, and the Sciences]

           The lumper story is one of the continuity and survival of the lineage; the splitter story is one of diversity and extinction of different lineages. Is the story of our ancestry like a tree trunk, or like a bush? The lumper inclines to the former; the splitter inclines to the latter. But those are significantly different shrubbery metaphors to be imposing upon the same sample of fossils. 

            Some decades after Simpson lodged his complaint, paleobiologist Tim White reiterated it, while reviewing a book on the history of "the" 22 species in our lineage: “Many of the putative species are chronotaxa; others are not even valid species in that sense. No one really thinks that available hominid fossils represent 22 separate species lineages in the last six million years.”[3]  Except, possibly, for the authors of the book under review.

           Or perhaps they didn’t really believe it either.  The assumption here that needs to be interrogated is that the fossil taxa of other groups of animals  are comparable – are made the same way, for the same reasons, of the same elements – as the fossil taxa of our own ancestors.  And that is the key error: Fossil animal species are units of biology; fossil human ancestors are bio-cultural units of narrative.  This is not to say that they don’t overlap, and that there were no zoological species in our ancestry.  The problem is that those zoological species are inaccessible to us, and so – rather like the angels sitting on the pinheads – we can see different numbers of species and tell quite different stories from the same empirical database.  This is consequently not an empirical issue at all, but a hermeneutic issue.

A recent book by a historian tells readers on its cover that 100,000 years ago “at least six human species inhabited the earth.”  Yet few practicing biological anthropologists would come up with the number six as the target number of species in the human lineage that inhabited the earth 100,000 years ago; and far fewer would acknowledge the particular six that the author does: Homo sapiens, H. neanderthalensis, H. erectus, H. soloensis, H. denisova, and H. floresiensis.  After all, “H. denisova” has not been formally named, and is based on the genome of a Siberian finger bone, which is itself simply a variant of the Neanderthal genome, which is not clearly a different species in the first place, since recreational genomic ancestry services (for about $200) will now identify the circa 5% of your genome that ostensibly comes from Neanderthals, which sounds very un-species-like.

            Is the tally right or wrong, then? It is actually neither.  We can’t say, because the zoological answer is inaccessible to us.  These are units of mythology, not of zoology.

            Another of the six presumptive species 100,000 years ago is Homo soloensis.  That name is a linguistic marker, denoting a particular set of Indonesian fossils, anatomically continuous with Homo erectus before and with Homo sapiens after.  As such, it is a named place-saver for a part of the human lineage – a rivulet, or capillary, or rhizome that better represents its elements metaphorically than a tree-limb does.  But in the words of Tim White, “no one really thinks” that this set of fossils represents a valid zoological species of their own.  There is no Homo soloensis. In other words, the ontological status of Homo soloensis is the same as that of Mother Corn Spirit. Neither is a unit of nature, but a unit of meaning or narrative which, to a believer, is perfectly sensible in the context of a story about origins. Homo soloensis is something, but it is not a zoologically familiar species, a fact of nature, so to speak. It is a named fictive ancestor, with more symbolic than naturalistic properties.  In the most fundamental way, human ancestry is self-consciously a story, and taxa like Homo soloensis and H. denisova are the components of this particular historical account.

            And likewise, Homo naledi, the newest major addition to our family tree. “But is it real?“ some journalists queried. Of course it’s real, you didn’t just imagine it.  “But is it real biologically?” they persist.  And that is my point: It doesn’t matter; Homo naledi is not an element of biology; it is an element of our origin story.  It is part of the bricolage of origin story-making.[4]  There is no true or false answer to Homo naledi as a zoological species; for the category of zoological species does not apply to things like Homo naledi.  The mistake here lies in assuming that Homo naledi designates a unit of zoology; that there is an underlying natural taxonomy in human ancestry that will be revealed by the proper ratiocination.  If you're looking for zoological reality, look for it at the genus level. It isn't there at the species level.

            Such is the long-standing taxonomic fallacy in grappling with the science of who we are and where we come from.  On a bio-political terrain, a preparation in biology is inadequate to comprehend the taxonomy, for it is not biological taxonomy.  To the extent that our ancestry is populated by species, those species are attempts to impose a taxonomic structure, which we assume ought to be there, upon an assortment of fossils from various times and places, with diverse anatomies, representing distinct lineages different from one another and yet connected in complex ways. There are a lot of ways of doing it, and they are all very sensitive to the conditions under which the science itself is practiced.

            If the Neanderthals and the Denisovans are not like zoological species, then what might they be like? And here we return to Linnaeus. They would be at most subspecies, as Linnaeus considered unfamiliar peoples to be.  In other words, the classification of extinct humans intergrades into the classification of extant humans. This fallacy – imposing taxonomic structure upon our ancestry, and mistaking the bio-political categories of our story for natural units – is the same fallacy we find at the heart of race.  For race, the meaningful story is “Who are we?” rather than “Where did we come from?” but the problem is the same, mistaking bio-political units of people for zoological units of people.  And those two questions are invariably intertwined, whether the answer comes from science or from any other system of explanatory narrative.

* This blog post is cobbled together from some forthcoming work, mostly Why is Science Racist? (Polity Press, 2017).

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[1] Simpson, G. G. (1945) The principles of classification and a classification of mammals Bulletin of the American Museum of Natural History 85:1-349, quotation from p. 181.

[2] Vulcan is the “Star Trek” planet, notable for the overbearing rationality of its inhabitants.

[3] White, T. D. (2008) Review of The Last Human: A Guide to Twenty-Two Species of Extinct Humans, by G J Sawyer and Viktor Deak. Quarterly Review of Biology 83:105-106, quotation from p. 105.

[4] Claude Lévi-Strauss (1962) used the term “bricolage” to refer to the available elements a mythmaker draws on, while tinkering with them to construct a resonant story. It was borrowed by molecular biologist François Jacob (1977) to argue that evolution is more like a tinkerer than like an engineer.