Mares and Stallions

Tom Wilkie

  • Games, Sex and Evolution by John Maynard Smith
    Harvester, 264 pp, £14.95, August 1988, ISBN 0 7108 1216 7

From the peacock’s tail to the quiet of an English rose garden, the dominant message of the natural world is that of sexual reproduction. We are so used to its omnipresence that we seldom question it. Few writers have seriously explored what life would be like in a sexless but otherwise human society, although Ursula Le Guin, in her very effective Science Fiction novel The Left Hand of Darkness has tried to do so. Whether consciously or not, Ms Le Guin set the action of her novel on a planet where perpetual winter provides an appropriately gray and colourless backdrop. But even she could not quite sustain the imaginative leap required: once a month her characters acquire sexual characteristics, but at random – an individual may be male one month and female the next.

Why do we have sex at all? There is so much of it about, and we take it so much for granted, that only a child, or an evolutionary biologist, would think of asking the question. And it turns out that sex is a very big problem for biologists, as John Maynard Smith explains in one of the most readable essays of this book, an essay that he has simply entitled, ‘Why sex?’. Maynard Smith is an emeritus professor of biology at the University of Sussex and the foremost theoretical biologist in Britain. Among his many contributions to the subject, he introduced the rigour of formal mathematics to reasoning about evolution, animals, species and biological systems. His speciality is the use of ‘games theory’ to explain how some animals managed to develop otherwise inexplicable ‘evolutionary stable strategies’ of behaviour (hence the references to ‘games’ in the title of this book). It comes as quite a shock to learn from someone as expert as he is that no one has the slightest idea of how sex came about in the first place.

Evolutionary biology has succeeded in providing a coherent explanation of all the manifold diversity of the natural world: an explanation that unifies, and yet allows us to marvel at and to value for its own sake, the diversity of forms and structures among the animals and plants in the world about us. The theory has been refined and developed since Darwin first formulated it, but the essence is still the same. There is a natural variation within populations of animals. Some traits will confer advantages upon their possessors, and these animals will survive preferentially to mate and pass on their favourable traits to their descendants. The theory can, for example, provide us with a complete – or as nearly complete as is reasonable to expect – account of the evolution of modern horses from the small lamb-sized Eohippus over the past 55 million years. Evolution can even account for the fact that Eohippus had three toes on its foot, and the modern horse has but one. But for all those 55 million years, the existence of mares and stallions has been a given, an input into evolutionary theory, not something explained by it. Some living creatures get on very well without sex. The bacteria and the viruses, for example, have neither male nor female yet they seem to prosper, as anyone who has suffered from a cold, flu or gastroenteritis will testify from personal experience. Some higher creatures are sexless, Maynard Smith tells us: dandelions, aphids and water fleas among them. But these are exceptions.

Professor Maynard Smith, I am pleased to see, favours what might be called the ‘used cars’ theory of sex. Basically this suggests that sex might have begun with two comparatively simple cells which might somehow have been damaged. They discovered that by pooling genetic material they could make themselves into one viable cell again. The process is similar to cannibalising two old bangers to make one car that will pass its MOT. But at this point the ‘theory’ of how sex might have begun is no more than a metaphor. It may be appealing, but it is not science.

There are, however, intriguing hints as to how one might take the story further. For example, there are two sorts of living cells: the bacteria have comparatively simple unstructured cells; whereas plants and animals lock up their DNA, the genetic instruction which they employ for reproduction, within chromosomes contained in the nucleus of the cells. Such ‘eukaryotic’ cells also have other complicated structures: plant cells have regions that are used for photosynthesis – that is, for converting carbon dioxide and the energy of sunlight into products useful for the plant’s growth. There is a hint here that such complicated structures may have arisen when cells without nuclei banded together to form colonies which eventually amalgamated and, by division of labour, shared out the various tasks of life. In this way, the cells acquired the unitary but complex structures that we recognise today. If this is true, it means that sex was not the only way in which simple organisms could band together for their own mutual advantage. It also raises the question of why, having gone to all the trouble of banding together to form one complex, the eukaryotic cells got involved in all the further complication of swapping genetic material with other cells.

The mention of nuclei raises other problems. Professor Maynard Smith points out that there are some fairly insuperable obstacles to the simple used-car model when it is applied to cells of reasonable complexity. The first, and most important, can be illustrated by the following example. We humans have 46 chromosomes in the nuclei of our bodies’ cells. We might therefore have been expected to produce a creature with 92 chromosomes the first time we mated – and so on, with a doubling of the number of chromosomes with each generation. Of course, this does not happen in practice. Instead there is a complicated system whereby cells that make up our sperm or eggs actually throw away 50 per cent of their chromosomes, so that an egg can accept new genetic material from the sperm produced by the other parent. Any theory of how sex evolved would have to explain how this complex mechanism evolved too.

It may disappoint some readers, but they will find no definitive answers to this problem in Professor Maynard Smith’s book. Indeed, although he illuminates many aspects of evolution and the natural world, his collection of essays is more in the way of a list of questions than a compendium of answers.

This is as it should be in any book about science. Nothing has been more pernicious in misinforming generations of schoolchildren about the nature of science than the elementary school arithmetic book which supposes that questions have answers and that these answers can be found at the back of the book. It is a deeply duplicitous thing to teach our young, many of whom will grow up assuming that the principles of the school text apply to their entire life and all its problems. It is contrary to the scientific method, for in science, as in life, there can be no assurance that a question has an answer. If we find what we think is an answer, then we cannot, in principle, know whether the answer is correct.

Professor Maynard Smith recounts how when he was a boy, he was introduced to science by reading books written for the lay person by the best practising scientists of the day; and in an essay entitled ‘Understanding science’ he posits two imaginary readers: ‘One is an intelligent but ignorant 16-year-old: myself when young. The other is an intelligent, but even more ignorant British civil servant bent on improving his mind.’ These readers are then used as the yardstick by which to judge the success of (the English translation of) a German popular science book. But I am not sure if, on balance, all Professor Maynard Smith’s essays would succeed if judged by this measure. Some assume a lot of technical knowledge and make no attempt to capture the interest of the ignorant. In a couple of places he has been let down by his publisher – why, for example, are we not told on the first page of the first essay that it is a review of James Watson’s book, The Double Helix, and was published in 1968? A lot of things have changed since then, and the reader needs to know, before reaching page 258, that the essay on page 3 is something of a period-piece. It would have been nice if Professor Maynard Smith had reworked the older essays, or at least added a comment at the end of each to say if and how his views had changed. Even so, he is right to say that the best way to learn about science is to read what leading scientists have to say about their subject and in the majority of these essays he proves himself a worthy successor to those whom he praises from his childhood reading.

Professor Maynard Smith lays much of the blame for the public misunderstanding of science squarely at the door of the mass media, drawing an unfavourable contrast between the science books written when he was young and the situation nowadays, where scientists’ words are filtered through a new breed of professional middlemen, the science journalists. He is particularly sceptical about television and worries about the anonymous voice-over that accompanies many TV documentaries. The BBC’s flagship science programme, Horizon, for example, employs this technique. Maynard Smith’s criticism is that the viewer does not know whose opinions are being expressed: there is just a series of excathedra pronouncements whose veracity the viewer must take on trust. In a sense, we are back in arithmetic textbook country here, only this time the answers are presented before the viewer may even have realised that there were any questions.

I tend to agree. But it does seem to me that Professor Maynard Smith, like many scientists who complain of the media’s trivialising and inaccurate ways, doesn’t understand the conventions and pressures involved in writing news stories for magazines and daily papers.

This is most noticeable at the point where he complains that his comments on the inadequacies of the media gained no public recognition when he presented them in his presidential address to the zoology section of the British Association for the Advancement of Science in 1983. The gentleman from the Times, he remarks, did not deign to report them. (I can assure readers that, whatever else may have gone wrong with that newspaper since it fell into the hands of Mr Rupert Murdoch, its science editor still merits the description of gentleman.) Journalists at the annual meeting of the BAAS are in an impossible situation. There are usually about ten lectures going on simultaneously, at opposite ends of the campus. The only hope that a journalist can have of covering the meeting properly is if the scientists make available full copies of their presentations in advance, via the BAAS management. I wonder whether Professor Maynard Smith gave out an advance copy of his speech. He does not tell us. Scientists perhaps don’t realise that, even when journalists are present at a lecture, they cannot be expected to understand a dazzling new insight in the time it takes the scientist to deliver it from the podium: a bit of warning helps.

In my experience, discussions of the public understanding of science always come down to mundane considerations of this kind. The criteria for running a science story in a newspaper are no different from and should be no different from those applied to any other story: it must be news; it must be interesting; it must be the sort of story that the readers of the paper will want to read and which will (with luck) attract more readers. There is no percentage in running another exposition of quantum mechanics, no matter how well researched or simply put. The Royal Society, Britain’s foremost academy of science (and indeed the oldest extant body of scientists in the world), has become so worried about the low level of public interest in science that it has set up a special Committee on the Public Understanding of Science. In one of the most positive steps taken so far, COPUS has encouraged a scheme whereby young scientists can spend six to eight weeks on secondment, working together with science journalists in the offices of newspapers, magazines, radio and TV. The scheme has been very successful and surprisingly few of the scientists have gone away still thinking that the media deliberately trivialise and misrepresent.

The real cure for the British disease of scientific ignorance lies in the hands of the scientists themselves. Why are there so few scientists who can write well about their subject? Apart from Professor Maynard Smith himself, there are only a handful. Stephen Hawking’s book, A Brief History of Time, has remained in the best-seller lists on both sides of the Atlantic for months. Stephen Jay Gould, the American evolutionary biologist, writes essays that are a delight to read. The late Sir Peter Medawar was a consummate stylist. But these few names aside, where, one asks oneself, are the modern equivalents of the great scientists whose books Professor Maynard Smith read so avidly as a child?