In and of itself, the concept of 'difference' possesses no significance. Its meaning emerges only in the context of a common standard against which the relationships, and hence the differences, between a set of objects, phenomena or events can be judged. Any discussion of differences, then, only makes sense in relation to a discussion about commonalities. In humans, the discussion about 'commonalities' usually turns on a discussion about 'human nature' - that is, the common nature that all humans are perceived to possess.
The concept of human nature is, of course, a highly contested one, and many deny the very existence of a universal essence to human life. In part, this denial has been shaped by the history of anthropology. Nineteenth racial science had viewed humans as entirely moulded by the laws of nature, and the differences between human groups as the consequence of distinct evolutionary paths. In response, twentieth century anthropology rejected not simply racial essentialism, but increasingly any form of essentialism. Human nature, and indeed the very idea of the human itself, has come to be seen by many anthropologists as suspect.
On the other side of the debate, sociobiologists and evolutionary psychologists view an understanding of human nature as a fixed quality that constrains the human condition, and fundamental to any understanding of what it is to be human. The denial of human nature, Steven Pinker suggests, 'distorts our science and scholarship, our public discourse and our day-to-day lives'.
Looked at in a certain fashion, though, the distance between sociobiologists and relativists is not as profound as it might sometimes seem. Virtually all cultural relativists accept the idea of the 'psychic unity of Man' - that is, a common set of mental abilities that ensure that no human group is inherently superior to another. Virtually all sociobiologists accept that cultural distinctions give rise to a multitude of variations in human behaviour and beliefs. Hence, in an influential paper on 'The Scope of Anthropology', Claude Levi-Strauss argued that 'universal forms of thought and morality' pertain solely to 'biology'. The primatologist Frans de Waal, suggests that 'Culture... means that knowledge and habits are acquired from others... which explains why two groups of the same species may behave differently.'
Whatever their other differences, in other words - and I would not wish to diminish those differences - both sides in this debate accept that human unity is manifested solely at a biological level, while culture expresses its differences. What separates the two sides is largely a debate about the relative weights that should be attached to one's biological nature and one's cultural upbringing in shaping beliefs and behaviours. For sociobiologists humans are defined primarily by their nature. Given the pliability of human nature, relativists retort, the universal aspects of the psyche are largely unimportant.
Over the past half century, in other words, the debate about human differences and commonalities has become conflated with the nature-nurture debate. This conflation, I want to suggest, has been unhelpful for our understanding of both human nature and human differences. To explore this further I want to look more carefully at what we mean by human nature, and at what constitutes human universals.
Human nature is an inherently ambiguous term. On the one hand, it means that which expresses the essence of being human - or in Darwinian terms, species-typical behaviours and beliefs. On the other hand, human nature means that which is constituted in nature - which is usually taken to mean that which is the product of natural selection.
In non-human animals the two meanings are synonymous. What bats or sharks or chimps typically do as a species, they do because of natural selection. Many suggest that this is also true for humans. 'Evolutionary biology is fundamental to the study of human behaviour and thought', Leda Cosmides and John Tooby argue, because there are only two ways in which the human mind and its products can be designed - natural selection or divine intervention.
There are certainly species-typical human behaviours and social forms that are likely to be the products of evolved adaptations. But humans, unlike non-human animals, also forge universal values and behaviours through social interaction and historical progress. In this sense the human essence - what we consider to be the common properties of our humanity - is as much a product of our historical and cultural development as it is of our biological heritage.
The historicity of the human essence is revealed in a number of ways. The fact that humans are rational, social beings places certain constraints and creates certain opportunities that can shape the way we think about the world and organise our collective lives. Being rational we are able to apprehend both the regularities of the external world, and our social needs, and to draw conclusions from them. Being social creates certain opportunities common to all societies - the possibility of a division of labour, for instance - and imposes certain universal restrictions - such as the need for social order. Being both social and rational means that the common social goals, opportunities and constraints are often tackled in a similar fashion in different societies.
A good illustration of the way that human universals can be the product of social, not biological, development, can be seen in an example that is often cited as evidence for the view that universals are evolved traits. Over the past three decades a number of anthropologists have shown that many pre-industrial societies have developed taxonomies of the natural world that are remarkably consistent with the modern Linnaean system. The anthropologist Brent Berlin, who pioneered the cross-cultural society of biological classification, suggests that there exists a 'default' taxonomy characteristic of all traditional, or folk, societies. All such societies can recognise hundreds of species - far more than they eat or utilise in other ways - which they classify according to a complex hierarchical system. All regard the rank of species as the most important in the hierarchy, and there is a remarkably high correspondence between what such societies regard as species and what modern biologists do.
All this has led some anthropologists to suggest that humans possess a special mental faculty whose job it is to distinguish between animate and inanimate objects and to classify animate ones. The rules by which people classify the living world are common to all cultures because they are hardwired into our brains.
It is possible, however, to understand the universality of such taxonomic rules in a different way. All humans habitually classify all manner of things from books to weather systems. All pre-industrial societies require a good grasp of relations within the natural world. And while the flora and fauna of, say, Europe and Australia may differ, the relationships between classes of organisms remain the same the world over. The objective world, in other words, is a constant. Given all this, it is likely that many different societies are both driven to classify the natural world, and compelled to establish similar kinds of rules about the manner in which the natural world is parcelled up.
There is another way of putting this. If the capacity for biological classification is an evolved trait, it could only have arisen because the brains of some of our ancestors noticed regularities in the living world. Such people may have been better at finding food or avoiding predators; they would have survived and reproduced better than those who did not notice the regularities, and hence the trait would have spread through the population.
But here's the catch. If there exists enough regularity in the living world, and sufficient selection pressure, for nature to design a brain module that can classify the living world, then there also exists sufficient regularity and pressure for humans to create such a taxonomy-maker empirically. If nature can do it without foresight, so can humans with a little forethought. If, on the other hand, there is insufficient environmental structure or external pressure for humans to generate this taxonomy empirically, then neither is there likely to be for it to evolve naturally.
I do not know - and nor does anyone else - whether the apparently universal capacity to classify the natural world along similar lines is an evolved trait or not. All I am suggesting is that for humans, unlike for non-human animals, such universals can arise without the help of nature because humans are rational, social beings.
A second expression of the historicity of the human essence lies in its normative quality. Salman Rushdie has suggested that if human nature did not exist, then 'the idea of universals - human rights, moral principles, international law - would have no legitimacy'. This belief has become central to much sociobiological thinking, and indeed invests it with a certain moral authority. If our moral capacities were not evolved, the argument runs, then we could not develop a common moral universe. Both Steven Pinker and EO Wilson have suggested, for instance, that revulsion at the practice of slavery is part of human nature because we have a natural aversion to being humiliated and imprisoned. Francis Fukuyama insists that human values are rooted in human nature and hence that liberal capitalism lies at the end of history because its beliefs and institutions 'are grounded in assumptions about human nature that are far more realistic than those of their competitors'.
I have no doubt that our capacity for moral thought is likely to be an evolved trait. But this is not the same as saying that values are natural. Take the question of slavery and the idea of equal human worth. For most of human history, slavery was regarded as natural as individual freedom is today. Only in the past two hundred years have we begun to view the practice with revulsion. Why? Partly because of the political ideas generated by the Enlightenment, partly because of the changing economic needs of capitalism, and partly because of the social struggles of the enslaved and the oppressed. Certainly, today we view opposition to slavery as an essential aspect of our humanity, and see those who advocate slavery as in some way inhuman - but it is a belief that we have arrived at historically, not naturally.
Human nature is neither an illusion, nor simply an expression of our rootedness in nature. It is a concept that only makes sense if we understand it historically, and normatively. The human essence is not something simply given to us but is also made by us. In this sense, human universals are also, paradoxically, historically contingent.
The unique character of human universals arises out of the existence of humans as rational, social beings with the power to act as political subjects - with the power, in other words, to transform themselves and their societies through reasoned dialogue and activity. All animals have an evolutionary past. Only humans make history. The existence of humans as a uniquely history-making species has moulded the relationship between universals and particulars in human society, between human nature and human differences. Humans are able both to create social distinctions (and to view them as natural or fixed) and to ignore natural differences (as irrelevant to social intercourse).
Discussions about the relationship between human nature and human differences, however, whether rooted in natural or cultural views of human behaviour, have paid insufficient attention to the transformative character of human life. The conflation of the debate about universals and differences with the nature-nurture debate has established a dichotomy between biological universals and cultural differences, a dichotomy within which the sense of human agency has been lost.
On either side of the debate, both what we have in common and what differentiates us has come to be viewed as fixed. And, as cultural relativism has given way in recent years to biological universalism, so both our commonalities and our differences are seen increasingly as rooted in nature. Or, as the philosopher John Gray has recently put it, 'The good life is not found in dreams of progress, but in coping with tragic contingencies.'
To restore balance to the discussion of human commonalities and human differences, we need to do three things: first, to distinguish the debate about universalism and relativism from the nature-nurture debate; second, to understand human nature not simply in naturalistic terms but also as something historical created; and thirdly to restore the concept of human agency into the discussions of both human nature and human differences.