Are humans different from animals in degree or in kind? Tim Ingold argues that the new Darwinism, far from offering a solution, is riddled with contradictions.

Do human beings differ from other animals in degree or in kind? This venerable question, which has exercised the minds of western thinkers for centuries, continues to lie at the heart of contemporary debate. I believe that Neo-Darwinian theory, far from offering a solution, merely reproduces the problem in its founding assumptions. It is a problem, indeed, that lies at the heart of western thought and science, namely that we have no way of comprehending the continuity of the living world save by taking ourselves out of it. If we are to seek an understanding that would re-embed our experience as human beings within the continuum of organic life, as I believe we should, then we will have to recast the whole way we think about evolution. And this will require a shift that modern biology, locked within a framework that for its practitioners is non-negotiable, seems ill-prepared to countenance.

The idea that no radical break separates the human species from the rest of the animal kingdom is an ancient one, going back to the classical doctrine that all creatures can be placed on a single scale of nature or Great Chain of Being, connecting the lowest to the highest forms of life in an unbroken sequence. Every step along the chain was conceived as gradual or, as the saying went, "nature never makes leaps". Darwin, in his theory of evolution by natural selection, replaced the image of the single chain with that of a branching tree, but the idea of gradual change remained. According to the view of the evolution of our species that may be found in any modern textbook, our ancestors became human by degrees, over countless generations. An unbroken sequence of forms is supposed to link the apes of some five million years ago, from which both human beings and chimpanzees are descended, through the earliest hominid creatures of two million years ago, to people like ourselves - certified humans of the "anatomically modern" variety: Homo sapiens sapiens.

As an account of human biological evolution that may be all very well, but what about human history? Theorists of the 18th century, cleaving to the philosophy of the Enlightenment, tended to think of human history as the story of man's rise from primitive savagery to modern science and civilisation. Yet they were also committed to the doctrine that all human beings, in all places and times, share a common set of basic intellectual capacities, and in that sense may be considered equal. This doctrine was known as the "psychic unity of mankind". Differences in levels of civilisation were attributed to the unequal development of these common capacities. It was as though allegedly primitive peoples were at an earlier stage in their pursuit of a core curriculum common to humankind as a whole.

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In short, for these 18th-century thinkers, human beings differed in degree from other creatures with regard to their anatomical configuration, but nevertheless differed in kind from the rest of the animal kingdom insofar as they had been endowed with minds - that is with the capacities of reason, imagination and language - which could undergo their own historical development within the framework of a constant bodily form. Even Linnaeus, who took the bold step of including human beings within his taxonomic system under the designation Homo, was hard-pressed to discover any definitive criteria by which to distinguish anatomically between humans and apes, choosing instead to identify the human distinction by means of a word of advice: Nosce te ipsum - "know for yourself". Only humans, Linnaeus thought, could seek to know, through their own powers of observation and analysis, what kinds of beings they are. There are no scientists among the animals.

The immediate impact of Darwin's theory of human evolution, set out in his 1871 volume The Descent of Man, was to subvert this distinction. Differences in mental capacity were attributed to different degrees of development of a bodily organ, the brain, such that civilised people were supposed to have larger, better organised brains than primitive people, just as the brains of the latter were supposed to be larger and better organised than those of the apes. Human history - or what had now come to be called the evolution of culture - was understood to march hand-in-hand with the evolution of the brain, through a process of natural selection in which the hapless savage, cast in the role of the vanquished in the struggle for existence, was sooner or later destined for extinction. When the co-discoverer of natural selection, Alfred Russell Wallace, suggested that the brains of primitive savages might be just as good as those of European philosophers, and therefore designed to be capable of more than was actually required of them under their simple conditions of life, he was dismissed as a spiritualist crank. For natural selection, it was argued, will furnish the savage only with as much brain power as he needs to get by.

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But of course Darwin was wrong and Wallace was right, although few give him credit for it. The brains of allegedly primitive hunter-gatherers are just as good, and just as capable of handling complex and sophisticated ideas, as the brains of western scientists and philosophers. However, racist notions about the innate mental superiority of white European colonisers over indigenous peoples were remarkably persistent in biological anthropology. It was really not until after the second world war, and the atrocities of the Holocaust, that such notions ceased to be tolerated in scientific circles. But this left the Darwinians with a problem on their hands. How was the doctrine of evolutionary continuity to be reconciled with the new-found commitment to universal human rights? The Declaration on Human Rights of the United Nations asserted, once again, the fundamental equality of all humans - present and future and, by implication, past as well. And if all humans are alike in their possession of reason and moral conscience - if, in other words, all humans are the kinds of beings who, according to western juridical precepts, can exercise rights and responsibilities - then they must differ in kind from all other beings which cannot. And somewhere along the line, our ancestors must have crossed a threshold from one condition to the other, from nature to humanity.

Faced with this problem, there was only one way for modern science to go - that is, back to the 18th century. Indeed the majority of contemporary commentators on human evolution appear to be vigorously, if unwittingly, reproducing the 18th century view in all its essentials. There is one process, of evolution, leading from our ape-like ancestors to human beings of a biologically (or "anatomically") modern form; another process, of culture or history, leading from humanity's primitive past to modern science and civilisation while leaving us biologically unchanged. History, as one eminent psychologist, David Premack, has recently pronounced, is "the sequence of changes through which a species passes while remaining biologically stable". And of all the species in the world, only humans have it.

Now it is a remarkable fact that whenever scientists are concerned to stress the evolutionary continuity between apes and humans, the humans are almost always portrayed as ancient hunter-gatherers (or if modern hunter-gatherers are taken as examples, they are commonly regarded as cultural fossils, frozen in time at the starting point of history). It was under conditions of life as hunter-gatherers, in the Pleistocene era, that the biological capacities evolved - bipedalism, tool-use, big brains, male-female pair-bonding, and so on - that are supposed to have made us human. Thus every one of us carries, as a fundamental part of our biological make-up, a set of capacities and dispositions that originally arose as adaptations to the requirements of hunting and gathering in Pleistocene environments. Of course, what was adaptively advantageous to our hunter-gatherer predecessors may not be so well suited to life in densely populated, urban environments. A lot of the endemic problems of modern civilisation, from road accidents to mechanised warfare, have been attributed to this. However, the idea that even the modern city dweller is afflicted by this legacy from our evolutionary past lies behind much of the continuing interest in contemporary hunters and gatherers whose form of life is thought to resemble most closely the condition of ancestral populations, and whose study might therefore reveal to us something of our inner nature. Inside each of us, it is supposed, there is a hunter-gatherer struggling to get out.

Evidently, western thought and science, including the science of evolution, needs hunters and gatherers - so much so, indeed, that had they not existed they would almost certainly have had to have been invented. The category "hunter-gatherer" is, in effect, constituted by the intersection of two axes, respectively of historical and evolutionary change, whose separation is logically necessary in order to preserve the claim of science to deliver an authoritative account of the workings of nature in the face of the recognition that the scientist - who, like the rest of us, is only human - belongs to a species that has itself evolved to its present form through a process of variation under natural selection. Humans did not evolve as scientists, but they are thought to have evolved with the capacity to be scientists, and for that matter to read and write, to play the piano, drive cars, and even fly a rocket to the moon; indeed to do anything that human beings have ever done or will do. Cro-Magnon man of 30,000 years ago, had he been brought up in the 20th century, could have been an Einstein. His brain was as big, and as complex. But the time was not ripe, in his own era, for this potential to be "brought out". Stretched between the poles of nature and reason, epitomised respectively by the contrasting figures of the hunter-gatherer and the scientist, is supposed to lie the entirety of human history.

There is a certain irony here. For biologists, who long ago co-opted the notion of evolution to describe what Darwin initially called "descent with modification", have been scathing in their criticism of those social scientists who have continued to use this notion in its original sense of a progressive unfolding of organised complexity. Yet they themselves cannot avoid precisely such a teleological view of history - as the unfolding of pre-evolved potentials or capacities!

In sum, contemporary evolutionary biology remains locked in the same contradiction that has been there all along. Its claim, that human beings differ from their predecessors in degree rather than kind, can only be upheld by attributing the total movement of history, from Pleistocene hunting and gathering to modern science and civilisation, to a social or cultural process that differs in kind, not degree, from the process of evolution. The detachment or disengagement of the human observer from the world to be observed, to yield the dichotomy between reason and nature, is indeed central to the project of natural science, including the science of evolutionary biology. Gazing into the mirror of nature, the scientist sees his own powers of reason reflected back in the inverted form of natural selection. Despite the claims of evolutionary theorists to have dispensed with the archaic subject/object and mind/body dualisms of western thought, they are still there, albeit displaced on to the opposition between the scientist, to whose sovereign imagination is revealed the design of nature, and the hunter-gatherer whose behaviour is interpreted as the output of innate mechanisms installed by natural selection, and over which he has no conscious control whatever.

Even as Neo-Darwinian biology proclaims the evolutionary continuity between humankind and the rest of the animal kingdom, it turns out that this continuity applies to humans as hunter-gatherers, not as scientists, and that the only way in which both scientists and hunter-gatherers can be brought within the same fold is by reasserting the essential distinction between humanity and nature, thereby compromising the thesis of continuity.

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To resolve this paradox, we need to find a mode of human understanding that starts from the premise of our engagement with the world, rather than our detachment from it. This is what I take to be the central task of my own discipline of social anthropology. And what makes anthropologists especially qualified to carry it out is their close familiarity with non-western understandings. If we turn, for example, from the western construction of hunter-gatherer society to the way in which people so designated understand their own sociality, we find that this understanding is fundamentally relational, in the sense that persons are perceived to come into being, along with their particular capacities, dispositions and identities, within the context of a history of continuing involvement with others. To put this in rather more formal terms, human capacities are not pre-specified, in advance of development, by virtue of some innate endowment that every individual receives at the point of conception.

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Rather, such capacities arise as emergent properties of the total developmental system constituted by virtue of an individual's situation, from the start, within a wider field of relations - including most importantly, relations with other persons. In short, social relations, far from being the mere resultant of the association of discrete individuals, each independently 'wired-up' for co-operative or altruistic behaviour, constitute the very ground from which human existence unfolds.

The implications of this view for the structure of evolutionary theory are profound. For it strikes at the heart of the central principle on which orthodox theory distinguishes between evolution and development, or between phylogeny and ontogeny. The basis of this principle is that what every individual receives from its predecessors is a context-independent specification of form, the genotype, that is then "realised", in the course of its life history, in the concrete form of an environmentally specific phenotype. Ever since the so-called Lamarckian doctrine of the inheritance of acquired characteristics was demolished by Weismann, at the close of the 19th century, it has been assumed that only the characteristics of the genotype, and not those of the phenotype, are carried across generations.

That the constituent elements of design are thus imported into the organism, as a kind of "evolved architecture", prior to the organism's development within an environmental context, is, I believe, one of the great delusions of modern biology. To be sure, every organism begins life with its complement of DNA in the genome, but on its own, DNA "specifies" nothing. There is no "reading" of the genetic code that is not itself part of the organism's development in its environment. And of course the organism does not begin life only with DNA. For the genome is contained within an egg which, even before fertilisation, is equipped through its own development with the essential prerequisites for launching further growth. And that egg exists not in a vacuum but in an already structured environment. Life begins, then, with DNA, in an egg, in an environment. Together these constitute a developmental system, and it is in the unfolding of this system, in the course of the life-cycle of the organism, that form emerges and is sustained.

What this means is that organisms, through their own practices in regard to one another, can participate actively in the evolutionary process by establishing the context of development for their successors. Human children, like the young of many other species, grow up in environments furnished by the work of previous generations, and as they do so they come literally to carry the forms of their dwelling in their bodies - in specific skills, sensibilities and dispositions. But they do not carry them in their genes, nor is it necessary to invoke some other kind of vehicle for the inter-generational transmission of information - cultural rather than genetic - to account for the diversity of human living arrangements. It is the very notion of information, that form is brought in to environmental contexts of development, that is at fault here. For it is within such contexts, in the movement of human beings' practical engagement with one another and with their non-human surroundings, that form is generated.

We can now see how, by taking the person-in-his/her-environment rather than the self-contained individual as our point of departure, it is possible to dissolve the dichotomy between evolution and history which has been the source of so much trouble and misunderstanding in the past. For if history be understood as the process wherein people, through their own intentional and creative activities, shape the conditions of development for their successors, then it is but a specific instance of a process that is going on throughout the organic world. Hence we do not need one theory to explain how apes became human, and another to explain how (some) humans became scientists. Once we come to recognise that history is but the continuation of an evolutionary process by another name, the point of origin constituted by the intersection of evolutionary and historical axes disappears, and the search for the origins of society, history and true humanity becomes a search after an illusion. Neo-Darwinism, the currently ruling paradigm of evolutionary biology, is - as I have tried to show - riddled with contradictions. Yet Darwin himself, of course, was no Darwininist, let alone a Neo-Darwininst, and he was a great deal more sensitive to the mutualism of organism and environment than many of those who nowadays yoke his name to their cause. But above all, Darwin was a true scientist, who was prepared to challenge the orthodoxy of his time when reason, evidence and intellectual honesty required him to do so.

It is curious, and not a little disturbing, that Darwin's heresy has now become a new orthodoxy, bordering in some cases almost on a faith. Its adherents, unable to recognise an epistemological argument when they see one, call for "robust" and testable hypotheses but are aggressively intolerant of any challenge to the framework of assumptions within which such hypotheses are generated. In their book, anyone who doubts the truth of Neo-Darwinian theory can only be either a crypto-Creationist or an unreformed social scientist who still clings to a pre-Darwinian notion of progressive evolution.

In the famous Oxford Debate of 1860, between T. H. Huxley and Bishop Samuel Wilberforce, the latter stood on the side of religion and the establishment against an upstart science. In today's debate, however, it is the Neo-Darwinists who are on the side of the establishment, while science itself has become their religion. In their claim that Neo-Darwinism must be right because there is no alternative, and in their dismissal of all doubters as heretics and enemies of science, they are surely revealed as the Wilberforces of the late 20th century.

This article is based on the text of a lecture presented at the University of Cambridge on February 17, as part of the 1995 Darwin Lecture Series on Evolution.

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Tim Ingold is professor of social anthropology at the University of Manchester.