Ian Tattersall

THE MONKEY IN THE MIRROR

Essays on the science of what makes us human

As Tattersall explains in his preface, this is a somewhat unusual book, being "a series of loosely connected essays on evolution and related subjects" rather than a tightly constructed argument. Presumably because of this, it lacks both an index and any references or even a suggested reading list, which is a rather unfortunate limitation, especially in view of its author's somewhat contentious views.

There are eight chapters or essays in all. The first two are on fairly general themes: the nature of science and of evolution. In these, Tattersall sets the scene for what follows. He is particularly keen to counter the idea that adaptation in evolution is "for" anything. Novelty arises on a haphazard basis and it is purely a matter of luck if it turns out to have a beneficial effect on survival and reproduction.

On this question of novelty in evolution, Tattersall boldly supports the view that quite radical innovations can appear in a population without warning ("Punctuated Equilibria"). The mechanism he proposes for this depends on a class of genes called homeoboxes, which regulate major developmental patterns. They are shared widely among different classes of animals and small changes in the timing of their effects can make huge differences. New forms of these genes may originate in the same way as other genes and are usually recessive, so could remain latent in a population until a sufficient number of them accumulated to make it likely that individuals would inherit two copies of the gene and so be radically altered in form. Natural selection would then decide whether the new variety survived or not. This is an intriguing idea if rather difficult to verify.

The rest of the book is concerned in one way or another with aspects of human evolution. In a chapter called "The Monkey in the Mirror", which is also the title of the whole collection, Tattersall considers the question of which animals are capable of recognizing their own reflection (only humans and some though not all apes), and considers the connection, or lack of connection, between brain size and intelligence. Although we often think that a large brain is what mainly distinguishes us from other species, pre-human hominids were not chiefly remarkable for the size of their brains. Instead, Tattersall identifies three features that he thinks are important in this regard: upright stance, the use of stone tools, and a "modern" body form.

Recognition of body form depends on the finding of more or less complete skeletons, which are rare; skulls are encountered more frequently but it is difficult to infer much about body build from these on their own. Plenty of early stone tools have been found but it is difficult or impossible to be sure which kinds of creature were using them or how toolmaking developed, although it is clear that even this relatively primitive use of tools required a certain degree of cognitive ability since it is beyond the capacity of living apes such as chimpanzees.

We do have one remarkable nearly complete early skeleton: that of the so-called Turkana Boy, dating from about 1.6 million years ago. He is, Tattersall says, a recognizably human individual ("very emphatically one of us"), and he also seems to appear suddenly, without obvious antecedents. Tattersall takes this to be an example of the innovatory process he touches on in his earlier chapter on evolution. However, it could no doubt be claimed quite plausibly that the absence of known forerunners is due simply to the inadequacies of the fossil record.

Tattersall has a complete chapter on the endlessly fascinating Neanderthals. He adopts the dominant but not universally accepted view that the Neanderthals were not ancestral to us but represent a separate species. He thinks it likely that they were killed off by our own ancestors and is dismissive of claims that the two species could have interbred. He doubts whether they could have had more than a primitive linguistic capability. He also questions the oft-repeated claim that they were adapted to a cold climate, since they existed for so long that they must have lived in a wide range of temperatures.

It is well known that anatomically modern humans existed for a long time without producing much evidence of cultural innovation. There is therefore a challenge to palaeoanthropologists to explain the sudden flowering of art and technology some 60,000 to 50,000 years ago. Tattersall says that this cannot have been due to a change in brain structure because the time frame doesn't appear to permit it, although this view seems rather at variance with his stated preference for sudden morphological changes. He prefers to believe that some kind of cultural innovation occurred: an idea that is reminiscent of those advanced by Julian Jaynes among others. He does not, however, suggest that this was language, which he seems to regard as an effect of the change rather than a cause. He thinks that language may have initially been spoken by children, something that has been discussed in more detail by Terrence Deacon.

Chapter Seven consist of a sustained attack on evolutionary psychology and sociobiology. Tattersall is scornful of the idea that our present-day behaviour is conditioned by our long evolutionary background as hunter-gatherers or that our psychology is dependent on our genes. However, I think there is a better case to be made out for such ideas than he allows, and his inevitably rather brief discussion of it is onesided. (For a more detailed review of the issues, see Kevin N. Laland and Gillian R. Brown.) The notion that we have been conditioned by our past in this way is, he believes, an example of the longing for a mythical golden age, and he prefers the view that our existence at the time was "nasty, brutish and short" (though he unfortunately wrongly attributes this well-worn phrase to Shakespeare instead of to Thomas Hobbes in Leviathan).

The final chapter looks to the future. It is fairly pessimistic about our chances of survival. As a consolation prize, however, if humanity is reduced to scattered pockets of survivors in relative isolation from one another there will be a chance for evolution to take off again; a large and unified population like ours today does not afford the fragmentation and isolation that is needed for selection to act.

Tattersall is an attractive writer. This is a readable and stimulating book that will appeal to anyone who takes an interest in current thinking about evolution. However, it makes no pretence of being dispassionate, and the aforementioned lack of a list of references will leave readers with little background in the issues not knowing where to turn for an alternative view.

19 March 2003