Humans: interesting but deadly

"There's nowt so queer as folk." This telling phrase, in Ian Tattersall's opinion, is probably the closest we will get to an accurate description of the individual human condition. He might easily have extended it to include the four million years of hominid evolution that he so masterfully surveys in Becoming Human: Evolution and Human Uniqueness .

This is one of those deceptively small books packed with information delivered in an informed but compulsive way. Measured and elegantly written, it is one of the most accessible state-of-the-art accounts of that most fundamental of stories - the origins of us. It is also cleverly punctuated by all the right caveats so necessary when dealing with such a complex and multidisciplinary set of issues.

Tattersall kicks off with gusto, dispelling notions of shuffling Neanderthals and primitive cavemen, and telling how, in the Europe of 40,000 years ago, these much maligned creatures were fairly rapidly displaced by the Cro-Magnons - the first European members of Homo sapiens . These beings were physically and intellectually indistinguishable from ourselves, their behaviour patterns (as inferred from archaeology) mirroring our own. Their remains reveal one of the recurrent themes in the book - the uniqueness of modern humans by virtue of their capacity for symbolic thought, as revealed in their unique material culture.

The evidence is impressive. At Mezhirich in Ukraine are 15,000-year-old dwellings composed of tons of artfully placed mammoth bones; from Sungir in Russia about 28,000 years ago three individuals were buried, each strikingly dressed in clothes onto which were sewn some 3,000 ivory beads (each one taking an hour to make), shell necklaces, carved-stone pendants, and artificially straightened mammoth tusks. Although the Cro-Magnons displayed a very modern diversity in their lives, from burial customs to stone tools, it is their artistic enterprises that bring them so close to ourselves.

The dazzling array of painted caves (not to mention musical instruments) reveals the existence of complex symbolic systems, though as is rightly observed the search for true meaning here is probably a fruitless exercise. Art was produced by different cultures over some 20,000 years, beginning at the startlingly early date of 30,000 years ago at the recently discovered Chauvet cave in southern France. Although these paintings have excited our imaginations and resonated with western traditions of representative art for 100 years now, intricate carvings also testify to the physical and cognitive skills of these people. Miniature animal figurines from Vogelherd, and a lion-headed (or costumed) human figure from Hohlenstein-

Stadel (both in Germany) testify to the qualitative differences between Cro-Magnons and all their various predecessors.

Occasionally, Tattersall's efforts to present both sides of an argument create an apparent contradiction. On one page we find the statement that deep cave sites were repeatedly visited, as evidenced by over-engraving and alteration of images, while on the facing page we read that it is probable that cave art was rarely visited by its makers. This, however, is a rare lapse in a polished performance.

Having hooked the reader, Tattersall moves on to unravel the underlying stories of our far-from-predictable rise to the top of the evolutionary pile. The relationship between brain and intelligence is explored by a comparative approach to humans and apes, outlining the pros and cons for using the latter, as our closest living relatives, for examining the former. The point is made that it is not just that we are more intelligent than apes but differently intelligent - capable of reflection and self-assessment, and able to manipulate our social and physical environments. Our fine-tuned behaviours are learned through culture rather than simply being shaped by the blunt instrument of adaptive evolution. Similarities and differences abound. Where chimpanzees and monkeys will opportunistically hunt other animals, humans plan, hunt cooperatively, and share the spoils. On the other hand, like humans, chimpanzee females transfer out, leaving the males to carry on the group's identity. More surprisingly perhaps, chimpanzees from Tanzania eat a dozen or so plants that are known to possess medicinal properties.

There are many seeming parallels between primates and ourselves. Humans are expert deceivers - an act that presupposes the deceiver is able to attribute states of mind to the deceived. Such behaviour has arguably been observed in chimpanzees. Similar cognitive abilities enable chimpanzees to use mirrors to see around corners, yet not apparently to recognise their own reflection. The author is undoubtedly right in saying that we cannot seek the causes of our intelligence by looking at primates, only gauge the similarities and differences between us and them. That most human of behaviours - tool making and useage - is also revealing. Capuchin monkeys and chimpanzees employ sticks and stones, yet they do so as learned behaviours within groups rather than as species-wide behaviours. Technicalities aside, it is nevertheless often difficult for us not to anthropomorphise primates, especially if we catch them wiping themselves after defecation or using banana leaves as umbrellas.

Language is the acid test, it seems. While chimpanzees vocalise to convey their emotional state, humans use it to convey often complex information upon which various strategies for survival can be assessed and engaged. The universality of human language is demonstrated by the existence of some 6,000 languages spoken across the world. Despite much wishful thinking, experiments with chimpanzees and gorillas reveal that they cannot grasp even the simplest notion of grammar or syntax, and there is no learning curve - they are easily outpaced by a human child. As Tattersall points out, there is no reason why we should expect a totally inarticulate species suddenly to produce the complex sounds arising from our own central neural mechanisms and speech-producing apparatus. Language is uniquely human, a quantum leap away from any other communication system in the natural world. The truth is plain - apes cannot plan, do not possess the capacity for abstract thought, and use the past only crudely as a guide for the future.

Language clearly is not a passing invention, but is tied closely to our physical evolution. In pursuit of this aspect of the story Tattersall examines the human brain - our most powerful organ. Human brains are three times larger than would be expected for a primate that weighs as much as we do. It continuously monopolises 20 per cent of our energy intake, even while asleep. Crammed into every human skull is a wrinkled cerebrum that would, if unfolded, cover 15 square feet. Yet it appears almost jerry-built. Rather than tidy pieces of engineering, brains seem to have developed by an opportunistic process of accretion and elaboration over a vast span of time.

A change of gear sees the author presenting a cogent review and assessment of ideas and trends over the past 200 years, asking what is evolution for? Seeing natural selection as a blind mechanism lacking direction, he nevertheless acknowledges that it lies at the heart of evolutionary change. We see how the idea of gradual evolution was challenged by the notion of punctuated equilibrium - where, for example, during a period of some six million years, trilobites underwent but one change - from eyes with 18 rows of lenses to eyes with 17 rows. He sees this as supporting the idea of long periods of species stability interrupted by brief events of speciation, extinction and replacement. In light of this, the palaeo-anthropologists' interest in projecting the origins of Homo sapiens as far back as possible into the past in linear fashion appears fundamentally misguided. Evolution, Tattersall states, is for nothing.

The story turns once more to the first hominids, which appeared in Ethiopia and Kenya about four million years ago and already appear to have walked upright. About 3.6 million years ago, Australopithecus afarensis left an 80-foot trail of footprints preserved in volcanic ash at Laetoli. The erect posture, so typical of humans, could have developed as an aid to seeing prey and predators, but equally might have originated as a body-cooling mechanism by reducing the amount of body area exposed to direct sunlight.

Archaeology begins about 2.5 to 1.8 million years ago when stone tools first appear, together with the first evidence of our own genus, Homo . This hominid, called Homo habilis , represented a giant move away from the apes in its inferred ability to comprehend the intrinsic qualities of the stone from which it made tools. From 1.9 to 1.4 million years ago a new creature emerged - sometimes called the African Homo erectus , though increasingly Homo ergaster . This creature had a brain capacity half our own, and a body similar to the modern human form, and was well suited to life in the open savanna. During this period also, 1.5 million years ago, there appears a technological revolution in stone tools with the arrival of Acheulean hand axes, sophisticated bifacially worked tools.

It seems as if, having freed itself from forested habitats, Homo ergaster 's wanderlust took it to Asia not long after it emerged on the African savannas. Coincidentally, at roughly the same time, the Pleistocene climatic cycle seems alternately to have stranded and reconnected these early populations, leading to a variety of local developments. In Europe, Tattersall argues that it was Homo heidelbergensis with its more or less modern brain capacity that was probably our ancestor as well as that of the Neanderthals.

The Neanderthals seem to provide the best available yardstick for assessing our own uniqueness. Their brains were similarly sized to ours but differently shaped, and they appear to have lacked the cognitive skills and guile of the Cro-Magnon humans who replaced them. Cro-Magnons arrived in Western Europe about 40,000 years ago, and after a relatively short 13,000-year period of co-existence (the nature of which we can only conjecture), Neanderthals disappeared, despite having lived together and shared the same stone tool tradition for some 60,000 years between 100,000 and 40,000 years ago in the Levant.

In this book, the author displays a magisterial command of the bewildering array of sources scattered across many disciplines. That these are woven so seamlessly into such a readable account is rare indeed. The human capacity for symbolic thought rather than just anatomical modernity is the key point to emerge. We are not simply an improved version of our ancestors, but a new concept - qualitatively different from all other life forms on the planet. Yet, while we are idiosyncratic and unfathomably interesting, we remain as potentially deadly to ourselves as well as to the rest of creation. The dark side clearly coexists with the light.

Nicholas J. Saunders is lecturer in material culture, department of anthropology, University College London.