The units of scientific anthropological origin narratives

Introduction

Biological anthropology is an interdisciplinary endeavor, and it is not enough to be a competent anatomist (or geneticist, or paleontologist, or ethologist). One has as well to acknowledge the institutional and intellectual home for this field. We are, after all, interested in who we are and where we come from as scientists because we are interested in who we are and where we come from as people. Monkeys don’t ask questions about their nature and origins; in fact, they don’t ask questions at all. Just framing those questions is a zoologically unprecedented act; and in any other society, the answers to those questions about one’s kind and ancestry would be found in the domains of kinship and origin myths. That makes them meaningful and value-laden in ways that stories about other things and other species are not (Stoczkowski, 2002).

Reciprocally, we are connected to the apes in meaningful ways, especially genealogically, which bears in turn on the philosophical question of what it means to be human. To the extent that such a question can be actualized as science, biological anthropology is the field that controls the relevant data (as paleoanthropology, primatology, human diversity and adaptability), and is thus positioned to be the most critical and relevant science (Marks, 2002; Calcagno and Fuentes, 2012).

There have been two central discoveries in the field of biological anthropology: In the 19th century, the recognition that we are descended from apes (Huxley, 1863); and in the 20th century, the recognition that human diversity and race are phenomenologically distinct, such that studying one is quite different from studying the other (Montagu, 1942). The meaning of those two discoveries was, and remains, contested. I wish to suggest that the major obstacle to an appropriately scholarly and scientific grasp of the meaning of those two facts is the belief that they are biological facts (like erythrocytes and wildebeest), rather than anthropological facts (like witchcraft and the family). This is not to deny the constructed aspects of scientific facts more generally. But while the dichotomy of nature and culture is false, we are often forced to work within its constraints, for example, when engaging with scientific racism. The biocultural nature of anthropological facts relative to biological facts may thus be considered to be ultimately a quantitative distinction, while still being a crucial one.

In this paper, I focus on the species, a concept that is as central and contested in zoology (Eldredge, 2015) as culture is in anthropology. And just as culture is easily reified as an unproblematic anthropological unit, so too is the species easily reified as an unproblematic zoological unit. The species in anthropology sits uneasily between its roles as a genetic or ecological unit and as a narrative element of an origin myth.

Our closest living relative

It is now well established that, with the data at hand, humans are most closely related to chimpanzees. This, however, obscures an important paradox, namely: you cannot deduce that conclusion from the anatomies of the species, but only from the available genomic data. You can find anatomical data that are consistent with that phylogeny (e.g. Richmond and Strait, 2000), but working with only their anatomies, you would either link chimpanzees and gorillas as closest relatives, or consider humans, chimpanzees, and gorillas to be a ‘trichotomy’ (Tuttle, 2014).

But if anatomy gives a ‘wrong’ answer to the relationships of the living apes, then how can we rely on anatomy to understand the relationships of extinct apes, when those are the only data at our disposal? Faced with this paradox at the base of the human tree, we may look a bit more closely at the genomic union of human and chimpanzee, and at the most appropriate representation of their evolutionary relationships.

Figure 1 illustrates three such representations, and each tells a different story about human origins. Figure 1a is the one most often shown in introductory textbooks. The gorilla branches off one or two million years before humans and chimps split from one another, and speciation is effectively instantaneous and complete. Figure 1b is the one actually favored by the genomic researchers (Patterson et al., 2006; Scally et al., 2012), because a large chunk of their data (about 30%) gave discordant phylogenetic results. Here, gorillas also split off early and completely, but then returned for a foray into the chimpanzee gene pool; the polite term is introgressive hybridization. In fact, there has always been considerable ambiguity, discordance, and overlap in the genomic datasets, and unclarity as to their meaning. Trans-species buggery? Two nearly simultaneous speciation events? Random mis-sortings of the gene pool? Or perhaps, as in Figure 1c, these ambiguities suggest that we ought to regard speciation as a long-term process that took a couple of million years to complete. OPEN IN VIEWER

There are several bio-historical explanations that are consistent with this latter pattern, involving the variables of time, geography, and demography. While there are many things that might be true about the branching histories of these species, the representation in Figure 1a is almost certainly false. For even if the chimpanzee and human are indeed one another’s exclusive closest relatives, the gorilla must be phylogenetically very close by, in the mix; a clean, wide separation of the gorilla has always been inconsistent with the molecular data (e.g. Rogers, 1993). Consequently I prefer the evolutionary history narrated in Figure 1c because it problematizes speciation; speciation here is a process, rather than an event.

Figure 1 also highlights two pieces of absent information, insofar as it illustrates not so much the species themselves, but their gene pools. After all, the human and chimpanzee species have become very different anatomically, behaviorally, and ecologically; but we don’t see the emergence of those considerable differences in the histories illustrated in Figure 1. Rather, what we see is how little difference has arisen genetically in the human line over the last six million years or so. In other words, the illustration represents not so much their evolutionary histories as their genetic histories. The distinction between genetic difference and evolutionary difference is what allows us to use genetic change as a kind of clock to track the divergences of gene pools, precisely because the genetic change does not track radical adaptive evolutionary change in any readily retrievable way (King and Wilson, 1975). The units of biological heredity simply do not map on to units of the body; that is to say, while we have elbows and we have genes, we do not have ‘elbow genes’. Genetic change is thus distinct from general evolutionary change, while nevertheless cryptically causing evolutionary change.

Moreover, the figure omits another important datum from the genetic histories. If you compare the DNA of two chimpanzees from tropical Africa (which is where all chimpanzees are from) to the DNA of two humans from anywhere in the world, you find the chimpanzees to be at least five times more genetically different from one another as the two humans are (Kaessmann et al., 2001; Prado-Martinez et al., 2013). Likewise, with gorillas. Because of some combination of the effects of natural selection (as selective sweeps) and genetic drift (as founder effects), the extant human gene pool is considerably smaller than those of the apes. Imagining the human, chimpanzee, and gorilla gene pools to be comparable, particularly when trying to reconstruct their ancient histories and ancestries from their extant forms, is certainly a mistake.

The precise nature and extent of our ‘apeness’ is thus difficult to assess, as it is not detectable genetically (except for our general genomic similarity to ape genomes), and yet we are actually quite different from the apes: dentally, cranially, socially, intellectually, ecologically, and of course in how we move, thermo-regulate, and communicate. It is indeed a challenge to confront that dialectical relationship – being simultaneously apes and not-apes – without reducing the human condition to one of being ‘just’ apes (a position ridiculed by Julian Huxley in 1947 as ‘the nothing-but school’), or conversely overvaluing our zoological distinctiveness, and thereby obscuring our ape ancestry (e.g. Teilhard de Chardin, 1959).

Our species

After the Second World War, physical anthropologists began to reconceptualize the human species from a collection of discrete, nested pseudo-taxonomic units, or races, to a more fluid ‘widespread network of more-or-less interrelated, ecologically adapted and functional entities’, in the words of the Oxford anthropologist Joseph Weiner (1957).

If one no longer considers ‘the British’, ‘the Jews’, or ‘Europeans’ to represent discrete branches of a Darwinian tree, then how do we conceptualize them in a microevolutionary framework? Recognizing the connectedness of human populations across time and space, Earnest Hooton, as early as the 1930s, invoked the circulatory system to represent the literal ‘blood streams of the human races’. Franz Weidenreich used the railroad trellis. Ackermann et al. (2015) suggest flowing water, a system of rivulets.

It is an irony of intellectual history that at just the moment when anthropology was acknowledging the non-taxonomic structure of the human species, computational methods for constructing evolutionary trees were entering biology, and their most noteworthy application was to the human races. The geneticist Luca Cavalli-Sforza (e.g. 1974) argued that, phylogenetically, Europeans and Africans were more closely related to one another than either was to Asians.

From the standpoint of a half-century of hindsight, we can see that the question is badly framed, since those three gene pools are not discrete units of nature. Moreover, we now know that the taxa are not even comparable to one another, since the gene pool of Africans subsumes those of Asians and Europeans. As framed, the question is like studying the relations among Cetacea, Primates, and Mammalia, where the last category subsumes the first two, and consequently any answer is nonsense. By the 1990s, Cavalli-Sforza’s prestigious genetics research group at Stanford was still working on the relationships of the three races. From the DNA of 94 African pygmies, 64 residents of San Francisco’s Chinatown, and 110 ‘individuals of European origin from ongoing studies in our laboratories or reported in the literature’, they concluded sweepingly that the European gene pool is composed of a mixture of 65% African and 35% Asian elements (Bowcock et al., 1991).

Much of contemporary genetic anthropology is a reaction against Cavalli-Sforza’s influence in the 1990s. His brainchild, the Human Genome Diversity Project, raised issues of informed consent, ownership of blood, and responsibilities to participating communities, and was eventually denied the federal funding it sought, for its unwillingness to grapple substantively with those issues. The justification for the project was always somewhat unclear, but its website still explains that the data would be used to answer phylogenetic questions, ‘to see if, for example, the Irish are more closely related to the Spaniards or to the Swedes’. ¹ Of course the question can be posed, the DNA can be collected, and an algorithm can be written that will permit a computer to answer the question. But whether the answer will describe an accurate bio-historical reality – given the implicit assumption that the Irish, the Spaniards, and the Swedes are discrete, divergent, naturalistic, monophyletic entities – is unlikely.

Moreover, to operationalize its phylogenetic ambitions, the HGDP had to construct a fictive origin narrative of purity and isolation for the groups it hoped to study: ‘The populations that can tell us the most about our evolutionary past are those that have been isolated for some time, are likely to be linguistically and culturally distinct, and are often surrounded by geographic barriers’ (Cavalli-Sforza et al., 1991: 490). The geneticist’s assumption of purity had in fact been challenged by an earlier generation of anthropologists (Kluckhohn and Griffith, 1950). And even if you imagine human populations, like the KhoiSan, to be genetically isolated, it is far from obvious just what their DNA can tell us accurately about their evolutionary past, much less about ‘ours’.

In biologically reifying human populations, the HGDP transiently institutionalized the physical anthropology of earlier generations. They failed to see that what look like taxonomic entities in the human species are not, in fact, fundamentally naturalistic units, but bio-cultural units (Wade, 2004). In this sense, these human identities (race, ethnic group, linguistic family, nationality, continent-of-origin) are not biological facts but anthropological facts – co-constituted by some elements of ancestry and geography, and also of shared beliefs, political histories, power and status differences, and perceptions of meaningful similarity and difference.

And finally, where the HGDP rebuffed any suggestion that its work might reify race as a naturalistic category (Reardon, 2004), its work has indeed been taken – naively and speciously – in precisely that vein by some philosophers of science (Andreason, 2004; Spencer, 2014).

What unifies these two examples about ancestry and relatedness, at the very core of biological anthropology, is that they illustrate aspects of a general principle: These taxonomic entities are not like the taxa of biology. Thus, back in 1945, paleontologist George Gaylord Simpson complained about the taxonomy of human evolution: ‘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’ (Simpson, 1945: 181). He assumed that they ought to be like the taxa of biology, and that, as a biologist, he ought to be able to translate freely between the basic elements of human ancestry and diversity and those of the rest of the mammals – impartially and rationally. Yet perhaps the oldest anthropological fact is that nobody conceptualizes their own kinship and descent impartially and rationally.

Human ancestry

One can understand neither human diversity nor human ancestry if one assumes that named groups of people, or their ancestors, have a comparable taxonomic status to zoologically familiar taxa, like Proboscidea, Panthera leo, or Cebidae. It is not simply that populations connect genetically by gene flow, or horizontal gene transfer, or introgressive hybridization or other naturalistic means (Arnold, 2009), but that human populations in particular are also defined and bounded by non-biological criteria. While this is fairly obvious today for groups of living people, it is also true in subtler ways for human ancestors.

We often distinguish between taxonomic splitters (those colleagues who attribute anatomical diversity in the fossil record principally to species differences, thus splitting the sample into multiple taxa) and lumpers (those colleagues who attribute much of the visible variation to age, sex, microevolution, distortion, or pathology, thus lumping many specimens into few species). But this makes the practice sound capricious, when it is actually strategic, for there are other variables at stake (such as national pride, funding, and publicity) when you study who we are and where we came from, as opposed to what fruit flies are and where they came from.

Thus, a recent book by a historian casually explains that, 100,000 years ago, ‘at least six human species inhabited the earth’ (Harari, 2014: cover). 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, Homo neanderthalensis, Homo erectus, Homo soloensis, Homo denisova, and Homo floresiensis. After all, ‘Homo 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 (Reich et al., 2010), which is not clearly a different species in the first place, since for a modest fee recreational genomic ancestry services will now identify the circa 2% of your genome that ostensibly comes from Neanderthals.

Likewise, Homo soloensis identifies a set of fossils from a time and place with a recognizable set of anatomical features, continuous with earlier Homo erectus and with later Homo sapiens. As such, it is a 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 as a zoological species, Homo soloensis has about the same ontological status as Mother Corn Spirit. 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 elements like Homo soloensis and Homo denisova are, for lack of a better term, its bricolage.

Human macroevolution and microevolution are thus connected. How we classify Neanderthals is relevant to how we classify people, and the species we make in biological anthropology have bio-political consequences. We might imagine Neanderthals as a species, in contrast to a species of living humans. The abstract species ‘Homo neanderthalensis’ implies the possibility of a zoological taxonomy below the species level of both Homo neanderthalensis and Homo sapiens, living people. Alternatively, we might imagine Neanderthals as a subspecies, Homo sapiens neanderthalensis, in which case Homo sapiens is more expansive, and extant humans are recognized only at the lowest taxonomical level, the subspecies. This would leave living people as a subspecies, Homo sapiens sapiens, and would not permit any zoological taxonomy below that level.

Conclusion

As an interdisciplinary field, biological anthropology often struggles to differentiate itself from biology. But it actually has as much in common with kinship studies as it does with biology, being a particular case of the way in which human groups (in this case, scientists) conceptualize their relationship to other human beings and other kinds of beings. Indeed, to a large extent, one can see ‘biology-envy’ as a part of the problem that engulfed the biological anthropologists who embraced the Human Genome Diversity Project in the 1990s, in spite of its poor anthropological and ethical foundation (Weiss et al., 1992). Similarly, imagining the human lineage to be like the branches of a Darwinian tree, rather than like something else, leads to misunderstanding the nature of that ancestry and its components (Wolpoff and Caspari, 2000). The human lineage is neither a vine nor a bush; for while naturalistic shrubbery metaphors are popular in biological evolution, they fail to capture the elements of the human lineage. Consequently, a lifetime of working with zoological taxa may simply prove confusing as one attempts to extract meaning from the scientific stories of who we are and where we came from.

We have centuries of experience with the constant threat of naturalistic reification that human groups are under, which persists to the present. Zoology engages with subspecies or races, but not with oppression directed at those subspecies and races, and consequently it may not be a particularly useful model for biological anthropology, which must grapple with defining the boundaries of the human condition, as well as with the implications of classifying people.

The theoretical problem that I have tried to elaborate here is: Given that the pseudo-taxa which have traditionally constituted the elements of biological anthropology and populated its bio-historical narratives are not biological units, then what kind of units are they? They are bio-cultural units, I have argued, and confronting and manipulating that knowledge is in large measure what differentiates biological anthropology from biology. Anthropological taxonomy is not poor zoological taxonomy; it is different from zoological taxonomy in its goals, its structures, and its bio-political meanings. This may afford, I think, a more nuanced view of the difference between zoological and anthropological taxa than Simpson perceived and expressed in 1945.