Man and beast. One of our most cherished beliefs is that we are fundamentally different from animals. But modern scientists are increasingly questioning the concept of human exceptionalism. Can we still be certain about what it is that makes us human?

So You Think You're Human?

Felipe Fernandez-Armesto

<em>Oxford University Press, 190pp, £14.99</

There is an episode of Star Trek in which Data, the android who would be human, disobeys orders and puts at risk the life of his captain, Jean-Luc Picard, to prevent the destruction of machines he believes to be sentient. Far from being outraged, Picard congratulates Data and tells him that it is "the most human decision you ever made". In the Star Trek universe, humans are not simply physical beings but creatures of choice, capable both of defining right and wrong and of acting upon it. That is why Data's most heartfelt aim is to become human.

Felipe Fernandez-Armesto would probably have counselled him not to bother. Humans, he suggests, are not especially moral and certainly not superior to other beings. Defining what makes us human is, in fact, a difficult task. So you think you're human? Well, it's time you left your Star Trek fantasies behind and returned to the real world.

Fernandez-Armesto does not deny that human beings exist. But he sees humanity as an "elastic" category that should include, among other things, chimps, Neanderthals, the unborn - and probably androids. So You Think You're Human? is a history of "humankind", not of the beings that call themselves human, but of the idea that such beings exist. It is also a polemic against the very concept of humankind - at least as we conceive of it. Fernandez-Armesto writes:

Those of us who think we are human feel utter confidence in our human identity and our ability to recognise it in others . . . Yet our present concept is a recent contrivance: most people in most societies for most of history would have been astonished by such an all-encompassing category. Most of them, indeed, would have had difficulty in understanding the word "human" or finding an equivalent for it in their own languages, except as a way of designating members of their own group.

Fernandez-Armesto describes how, for centuries, humans have tried to establish the boundaries of humanity by excluding other animals, other human groups (hence the labelling of different races as "subhuman") and other hominid species, such as Neanderthals. Protecting the boundaries in this fashion, he argues, is both practically futile and morally suspect.

Yet the idea that humans should be viewed as distinct from animals is relatively recent. It cannot be traced back before the first millennium BC - "the 'axial age', when so much of our modern thinking was initiated or anticipated by sages in China, India, the near East and Greece". On the other hand, Fernandez-Armesto writes, "Our remote ancestors seem to have accepted without question that they were part of the great animal continuum. For the earliest creatures we might reasonably classify as human, this was actually an observable fact, since for most of the hominid past they coexisted with other, similar species." How Fernandez-Armesto can be so certain about what our remote ancestors thought about "the great animal continuum", I am not quite sure.

That a belief in human exceptionalism has coincided with the development of civilisation might suggest there is some merit to the idea of human distinctiveness. But no. Modern science, Fernandez-Armesto argues, sides with our remote ancestors against the sages of China, India, the near East and Greece. Over the centuries many thinkers have pointed to specific qualities - culture, reason, tool-use, language, morality - which, in their view, make humans distinct. Fernandez-Armesto collates the scientific evidence to show that none of these qualities is uniquely human. Chimps can make and use tools, and have been taught sign language. Many animals can reason about the world. In fact, animals seem to live very much as we do. Female bonobos have been seen to put dead rats on their heads - apparently a form of "haute couture". Chimps at the Yerkes primate centre in the US "gather together to sway and stamp in a concerted fashion" at the approach of heavy rain. This "looks like magical behaviour - evidence of a sense of transcendence or the power of prayer".

Fernandez-Armesto is clearly more impressed by the Jungle Book than by Star Trek. Real science, inevitably, is less cartoonish. Animal behaviourists often think of animals as if they were rational agents capable of making choices and driven by human-like motives. Why? Because it is a useful way of analysing behaviour. But, as the ethologist Patrick Bateson points out, "Attributing the power of making choices to an animal, so that we can do more imaginative science, does not mean, when our efforts are crow-ned with success, we have proved that the animal has chosen." In other words, even when animals behave in a human-like fashion, they do not necessarily do so for human-like reasons. Humans may be animals, but animals are not human. It is human sentimental-ity that transforms nature into Disneyland.

Science tells us that in some ways humans are similar to other animals and in some ways we are different. But the question of what meaning should be imputed to these similarities and differences is a political and philosophical issue, not a scientific one. Take, for instance, the question of culture. Fernandez-Armesto defines culture as "any widespread behaviour that is transmitted by learning rather than acquired by inheritance". By such a definition, many non-human animals are "cultured". Primatologists have so far discovered roughly 39 habits that distinguish groups of chimps from one another, including being able to hunt for termites with a stick, and using two stones as "hammer" and "anvil" to crack open palm nuts.

Humans, however, do not simply acquire habits from others. We also constantly innovate, transforming ourselves in the process, individually and collectively. There is a world of difference between a process by which certain chimpanzees have learned to crack open palm nuts and a process by which humans have created the industrial revolution, unravelled the secrets of their own genome, developed the concept of universal rights - and come to debate what it is to be human. All animals have an evolutionary past. Only humans make history.

This is not an argument that impresses Fernandez-Armesto. For most of history, he argues, most human societies have developed barely at a faster rate than the great apes. Indeed, the most successful humans are those who are most chimp-like. It is "glib" to hail the "great civilisations", which have "achieved spectacular progress, expansion and environmental transformation", as "models to copy". Rather, "the most successful societies are the ones that have changed the least, that have preserved their traditions and identities intact".

It is ironic that a historian as distinguished as Fernandez-Armesto should so easily dismiss the history-making capacity of human beings as irrelevant to our humanity. If you view the most chimp-like human behaviour as characteristic of our species, then it makes sense to deny the distinctiveness of humanity. But such denial is rooted not in science, but in philosophical pessimism.

In the final chapter, Fernandez-Armesto looks not to the past but to the future - to the consequences of the genetic revolution for our concepts of humanity. He is fearful, agreeing with Francis Fukuyama that "biotechnology will cause us in some sense to lose our humanity". However, if "we do not know what makes us human", how can we lose it? And if humanness is so "elastic" a concept as to encompass both Neanderthals and chimps, why can it not also encompass genetically engineered human beings?

The author's inclusive concept of humanity appears progressive: yet its consequences are often reactionary, as becomes clear in his argument about the unborn. "The unborn," he writes, "are the great underprivileged minority of our day, whom we can exterminate without a qualm." A definition of humanity that "excludes the unborn" is akin to a definition that excludes Jews or blacks. Abortion is a "massacre of innocents". Therapeutic cloning - the use of embryonic stem cells for medical purposes - is ethically "repellent". Fernandez-Armesto has opened the gates of humanity to the foetus - but only by closing the door to the rights of women and the needs of those suffering from myriad illnesses.

Fernandez-Armesto is right that there can be no single or simple definition of humanity. Humanity is not just a biological category but a normative one, too - it reflects the changing philosophical and moral conceptions we have of ourselves. Yet today, we are more uncertain than ever about what it means to be human. There is both anxiety about scientific pronouncements on human nature and fear that human progress and civilisation may be forces more for ill than for good. In an age that is unsure what humanity stands for, it makes sense to open the door and let everybody else join the club. The result is an anything-fits-humanity for an anything-goes age.

Kenan Malik is the author of Man, Beast and Zombie: what science can and cannot tell us about human nature (Phoenix)