The human of paleoanthropologists: an animal like any other?

4 The natural sciences reduce humans to the status of animals like any other, while philosophy, along with the humanities and social sciences, remain attached to the notion of human exception inherited from Descartes. This thesis, defended by Jean-Marie Schaeffer in La fin de l’exception humaine, has fueled the debate on the human and the animal in France. [2] However, we would like to show the limits of this alternative between biological reductionism and philosophical anthropocentrism through the example of paleoanthropology, insofar as this disciplinary field is traversed by a contradictory injunction. On the one hand, in fact, against the anthropocentrism of the glorious conceptions of the human developed in philosophy but also in natural history, this evolutionary science affirms the continuity of biological species, including the human, their being conceived as historical entities whose characteristics vary in the course of evolution and therefore cannot be defined by essential attributes. [3]

5 On the other hand, however, paleoanthropology has been marked throughout its history by the temptation of anthropocentrism, granting a superior place to humans in nature, whether in representations of evolution (Haeckel’s family tree in the form of a scala naturae influenced the description of Pithecanthropus erectus as the missing link at the end of the XIX^th century), taxonomic categories (from the order of the Bimanous in the nineteenth century to the family of hominids in the middle of the twentieth century) or even the criteria of interpretation of fossils (such as the cerebral criterion, more flattering than bipedalism). Moreover, anti-anthropocentrism has not always been the rule in evolutionary biology. Thus, George Gaylord Simpson, one of the main exponents of the synthetic theory of evolution, affirms the “validity of the anthropocentric point of view”, brushing aside the fashionable conception of the human as an animal, intended to “épater le bourgeois” [4] [astound the bourgeois] (in French in the text). On the contrary, maintains the paleontologist and systematist, “Man is the highest animal. The fact that he alone is capable of making such a judgment is in itself part of the evidence that this decision is correct”. [5] One can certainly identify in paleoanthropology a historical movement that leads from anthropocentrism (reflected in the accentuation of the differences between hominins and humans) to anthropomorphism (reflected in the accentuation of their similarities), as illustrated by the changes in the representation of Neanderthal Man. However, don’t these hominins who would be “ineluctably us” [6] renew an anthropocentrism of a new form, due to being widened?

6 One can also question a structural and literal anthropocentrism in paleoanthropology, which puts the human at the center in order to better bring out its specific characteristics. This science is very concretely confronted with the question of what constitutes the uniqueness of the “human”, at its different taxonomic levels; it uses criteria of definition of the human, necessary to the interpretation of fossils. Let’s take the example of bipedalism, which was imposed in the twentieth century as a fundamental adaptation making it possible to mark the origin of the human lineage and to establish that an individual belongs to it. [7] When it designates the human as the primate that stood upright on two feet, paleoanthropology only in one sense denies the glorious image of humanity; it also consecrates bipedalism as the ultimate “human uniqueness”, as the property possessed by all the representatives of the human lineage and only by them. Should we therefore conclude that paleoanthropology only proceeds to a temporalization of the anthropological difference, by showing us the passage from animal nature to human culture? Or is the question of anthropological difference reopened here in a completely new way?

Philosophy condemned to Zoocentrism?

7 Instead of conceiving the human as an extranatural or metaphysical being, separated from other living beings, the naturalist turn which marks contemporary philosophy has tried to naturalize the human, that is to say to reinscribe it in nature, by relying on the knowledge resulting from the natural sciences. [8] Philosophy would thus be summoned to see in the human only an animal like any other, by yielding to the ambient “zoocentrism” which places animality at the center of our humanity. [9] Paleoanthropology, however, provides resources that allow us to bypass this alternative, by approaching the question of the demarcation between human and non-human differently.

8 This discipline confronts us with forms that are neither “animal” – as is, for example, the tick dear to Jakob von Uexküll – nor “human” in the sense that the members of the current species Homo sapiens are. We are entering an uncertain zone here, with blurred boundaries, in which the most distant hominins (up to 7 million years for Toumaï) are presented as our ancestors, while the first members of our sapiens species seem to be only exaggeratedly “like us”, as the anthropologist Tim Ingold analyzes the ambiguous notion of “anatomically modern Man”. [10] Instead of being delimited by an anthropological difference that fixes its field of practice, paleoanthropology never ceases to “negotiate the animal-human boundary”, [11] a permeable and unstable boundary that distends and tightens with the movements of humanization of the great apes and the animalization of humans. [12]

A Bush of Hominins

9 Far from reducing humans to animals, paleoanthropology extends the field of anthropology by giving us access to the diversity of past human forms, in addition to the diversity of present or recent humanity documented by cultural and social anthropology. A proliferation of fossil discoveries has led paleoanthropologists to describe about fifteen new species, from Ardipithecus ramidus in 1995 to Homo luzonensis in 2019. Instead of a succession of increasingly human hominins, our evolutionary history would rather take the form of a bush of species, some of which may have coexisted and hybridized. [13] How can philosophy capture the latest developments in paleoanthropology? A certain caution is required here, not to banish the speculative dimension of philosophy nor to restrict it to a critical epistemology, but because the diversity in question here is not a directly observable datum: it is a property conferred on a set of specimens on the basis of quantitative and qualitative [14] arguments and translated by the number of taxa recognized in the human lineage.

10 Is this diversity real or constructed? Paleoanthropology has certainly never ceased to be traversed by debates on the human diversity of the past. Is Neanderthal man a species in its own right or an archaic variety of our own? Did the human lineage evolve through multiple ramifications or through the continuous transformation of the ancestral species, as suggested in the mid-twentieth century by the single species hypothesis? [15] Has the diversity in the human lineage been systematically underestimated, as assumed by the cladistic method (which emphasizes derived characteristics likely to be associated with new taxa) and the theory of punctuated equilibria (which emphasizes speciation episodes)? Far from being a consensus among paleoanthropologists, the reality and extent of hominin diversity continue to be hotly debated. [16]

11 Various biases are indeed likely to influence, in one direction or another, the estimate of diversity. They are due to the taxonomic and phylogenetic method used, to the constraints inherent in paleontology (how to determine if a handful of fossil specimens represent a new species?) but also to the anthropological issue, which gives a strong media and academic resonance to any description of a species presented as ancestral to present-day humanity and leads to shaping the past in the image of the present. The paleoanthropologist Tim White thus sees in the multiplication of hominin species the effect of a “populist zeal for diversity”, [17] fed by a confusion between diversity as a political value and as a biological fact.

12 Should we then consider the diversity of hominins as a theoretical construction, without biological reality? On the contrary, a consistent set of fossil evidence supports the hypothesis of significant synchronic diversity in the human lineage. However, these biases indicate that diversity is not only a quantifiable datum, but also a problem, which involves the concepts of diversity and variability in its biological aspect. According to a recurrent objection to the multiplication of hominin taxa, the underestimation of the variability of the species leads to the overestimation of the diversity of species in the human lineage. There would thus be a confusion between intraspecific and interspecific variation. Moreover, there is a whole variety of variations, which can be morphological, behavioral, sexual, pathological, ecological, geographical or temporal, but also of genetic origin (including the hypothesis that they result from a hybridization process), ontogenetic or epigenetic. What are the most relevant characteristics to justify the description of a new species? From fossil samples to living analogues, what is the appropriate comparative framework for estimating the variability of hominin taxa?

13 Would a clarification of the concept of species allow a more efficient enumeration of hominin species? The risk here is to shift the difficulty from the diversity of species to the diversity of concepts of species (about twenty different versions of which have been identified). Moreover, it would perhaps be more relevant to ask what concept of species can (and not must) be used for rare and incomplete fossil remains, for which the biological concept of species, based on inter-fertility, is not very operative. Thus, the morphological concept, based on the resemblance between specimens, is the dominant criterion in paleontology, although it can lead to interpreting any morphological change as an indication of speciation or to putting forward a morphology presented as unique (through a mixture of primitive and derived characteristics different from the others) to justify the description of a new species. [18]

14 Can we then hope that genetics will lift the uncertainties concerning human diversity in the past? Paleo-genetics informs us of genetic exchanges between Homo sapiens, Neanderthals and Denisovans, which feed the hypothesis of hybridization between these lineages, in a reticulated model of evolution. Thus, the species no longer appears so much as an entity separated from the others and closed on itself, but as a lineage with porous contours. Moreover, if genetics allows us to know the processes of human evolution, to trace the history of human populations, only morphology gives access to the results of evolutionary processes, thus to the diversity of anatomies and lifestyles. [19] Finally, the correlations between genetics, morphology and phylogeny are far from being clear. It is thus necessary to question the “molecular assumption” according to which “the degree of molecular similarity is a reflection of evolutionary closeness”, [20] but also to explore the molecular bases of the morphology underlying development to better understand the diversification of hominin species.

Identity and Alterity

15 Are these uncertainties concerning the extent of diversity in the human lineage likely to suspend the effort to assimilate knowledge from paleoanthropology through philosophical reflection on the human? We do not think so, for at least two reasons. On the one hand, uncertainty is common in paleoanthropology, because of the lack of data available to the discipline but also because of the lively debates that it fuels. On the other hand, the recognition and acceptance of human diversity in the past – whatever its biological reality ]– is in itself significant and constitutes an anthropological fact, according to the specular relationship highlighted in the first part of this article: knowledge of hominins of the past also says something about the humans that we are.

16 What, then, are the changes that the knowledge of human evolution induces in philosophical anthropology? The hypothesis of a diversity of hominin species calls for us to rethink anthropological difference in a new way, which is now irreducible to the identification of “human uniqueness” in human evolutionary history. If the essentialization of characteristics that vary over time is problematic, the hypothesis of a bush of hominins evolving in neighboring lineages suggests moreover that characteristics traditionally considered as uniquely human, whose emergence tends to be thought of as a single event, may have evolved several times and in several forms. Thus, the diversity of anatomies revealed by some recent fossil discoveries could indicate a diversity of locomotor adaptations in the human lineage, so that there would be not one bipedality, but a plurality of bipedalities. [21]

17 If the trail of “human uniqueness” seems to be slipping away, is it necessary to renounce all anthropological difference? On the contrary, we would like to show that the current knowledge of paleoanthropology requires philosophy to take up this question again. Far from reducing the human to the animal, paleoanthropology allows to extend the field of anthropological differentiation, not by digging a difference of essence or nature, but by exploring another difference – o longer between human and non-human, in the form of a separation, but between forms of humanity, in the form of a relation. This experience of otherness does not consist in confronting other humans, but rather other humanities; the question is thus no longer only that of anthropological difference, but also that of a new anthropological diversity, which involves the constitution of a true paleo-anthropology, in dialogue with social and cultural anthropology.

18 Through the confrontation with the otherness of other humanities, a new avenue is opened up to us to define the human, by circumventing the difficulties related to the search for “human uniqueness”. It is a question of asking how the human is defined not in itself, by unique properties, but as a variation in a family of related and yet differentiated forms. This new perspective requires philosophy to propose a conceptual scheme allowing us to understand the human diversity of the past, now documented by paleoanthropology, at the cost of a paradigm shift.

19 This requires, first of all, a change of method, or more precisely a renewal of the usual comparative method in paleoanthropology, which compares fossil specimens with individuals of present-day species, as well as fossil specimens with each other. The comparative method proceeds according to two principal modes: to the typological mode, which brings its objects closer to a type constituting the point of comparison, is added a second mode of comparison, which “does not rest on the subsumption of various cases under a category defined by a set of common characteristics, but on the definition of a network of related forms”. [22] This process, which privileges the definition of variation over that of type, was implemented at the beginning of the nineteenth century in comparative grammar and biology, and then, as Gildas Salmon has shown, in the anthropology of Franz Boas. However, the plurality of past human forms in paleoanthropology requires the constitution of an anthropology conceived as “knowledge of networks of variants”, [23] in line with a reticulated model of evolution that represents human phylogenetic history in the form of a network of lineages.

20 Indeed, this paradigm shift also involves a change of model, that is to say, of the way in which paleoanthropology represents its object. The history of this science is marked by the transition from a linear and gradual model, distant heir of the scala naturae and the chain of being, [24] to a bush-like model for thinking about kinship and evolution. But this substitution of the bush for the ladder cannot without naivety be conceived as the unsurpassable horizon of scientific progress. Aren’t the ladder and the bush both ultimately derived from the same arborescent model, rooted in the Aristotelian theory of difference formalized by Porphyry’s tree, and still predominant in thinking about anthropological difference? [25] What model can we then imagine in order to understand the diversity of hominins? The concept of rhizome proposed by Deleuze and Guattari may provide a trail here. “Evolutionary schemas would no longer follow models of arborescent descent going from the least to the most differentiated, but instead a rhizome operating immediately in the heterogeneous and jumping from one already differentiated line to another”, [26] the authors of AThousand Plateaus propose, analyzing the role played by viruses in the transport of genetic information. This new model could be relevant for understanding genetic exchanges between species, for which paleoanthropology provides clues. It is no longer a question of reasoning only in terms of historical individualities but of the relations that these entities maintain with variants, as a certain trend in cultural anthropology does by giving itself as an object of study the “transversal circulation between divergent series”. [27] Here a new opportunity is opened up to overcome the divide between biological anthropology and cultural anthropology, between natural sciences and cultural sciences.

21 On the double level of epistemology and ontology, involving both the method and the object of knowledge, this paradigm shift affects the way in which the human is grasped in a system of representation, but also the place of paleoanthropology in the contemporary intellectual landscape. How can paleo-anthropology be truly constituted as anthropology, in the passage from typology to variation and from tree to rhizome? In this new perspective on the human, Homo sapiens is no longer just the point of comparison, the invariant type from which to distribute similarities and differences; it discovers and represents itself as a variant in a set of variant forms of humanity. In an unexpected way with regard to disciplinary boundaries, paleoanthropology then resonates with a certain current of the contemporary cultural anthropology, which approaches in a new way the variations of conceptual schemes between peoples. Thus, Patrice Maniglier writes about the anthropology of Eduardo viveiros de Castro, the comparative method that characterizes it consists in “making the subject of the comparison appear as a variant of what he believed to be its object” and “in discovering that the type itself is a variant, which means that it is defined by its position in a set of quite precise transformations.” [28]

22 If this paradigm shift offers paleoanthropology a more relevant conceptual framework for its objects and a better insertion into anthropology, it is essential to identify the irreducible differences by which paleoanthropology and this cultural anthropology vary from each other. [29] Paleoanthropology thus presents itself as an anthropology without symmetry or reciprocity: if the human sapiens can know itself in its difference in relation to the human variants that preceded it, no reciprocity is possible, so much so that the opposition of the subject of knowledge and the known object seems to be unsurpassable here. No confrontation is possible here with the living alterity of the concepts and behaviors of these other humans, from which arises, nevertheless, the experience of equivocation so fundamental in the trend of cultural anthropology that we have mentioned. [30]

23 But is this absence of reciprocity only and irreducibly a deficiency? On the contrary, it allows us to experience what we are as a human species by confronting us with a radical otherness that is nonetheless capable of being apprehended as variation. The pluralization of the human in no way implies the leveling of humanities by the negation of all difference: the confrontation with the otherness of disappeared human forms appears on the contrary as a condition for identity and self-knowledge, thus offering an alternative avenue to that of the “human uniqueness”.

24 The question of the possible uses of paleoanthropology by philosophy can find new answers here. Does the latter only have the function of helping the paleoanthropologist – or the prehistorian – “to develop a historical and critical study of their own discipline”? [31] Or should we rather consider, as Philippe Grosos rightly remarks about prehistory, that paleoanthropology provides philosophy with resources that allow it to rethink some of its fundamental concepts in a profoundly different way? The highlighting of a human diversity of the past allows such a renewal: if the relationship to the other has always nourished anthropology, [32] paleoanthropology makes us discover an otherness, strange as much by its temporal distance as by the fossil traces by which it is known to us, revealing a vast field of study which remains largely to be surveyed.