A game without odds

Baseball and cricket, like new and old-world monkeys, had a common ancestry but went their separate ways. Both sports have provided striking images to characterise such evolutionary trends. "One gets from cricket a dim glimpse of the youth of the world," wrote Prince Ranjitsinhji in 1897 in his best-selling The Jubilee Book of Cricket. "There is generous life in it, simplicity and strength, freedom and enthusiasm, such as prevailed before things in general became quite as complex and conventional as nowadays."

Baseball appeals to other evolutionary scenarios. The fact that it has not changed its rules since 1893, while cricket has on several occasions, casts it as a struggle between players and a capricious system over which they have no control. In the 1960s, when pitchers got the upper hand over hitters, natural selection intervened as the league's administrators lowered the pitching mound so returning averages to normal the next season. The intensity of baseball, provoked by such struggle, reminds me of the famous comment by Bill Shankly, manager of Liverpool FC, that football isn't a matter of life and death because it's much more serious than that.

So too is evolution. Stephen Jay Gould shows why in his first full-length book since Wonderful Life by examining the all-important themes of progress, variation, complexity and trends in evolution as well as the failure of modern baseball batters to achieve the same seasonal averages as former giants such as Babe Ruth and Joe DiMaggio. Wonderful Life explored the contingency of evolution after the explosion of multicellular organisms 530 million years ago. As Gould says, re-run the tape of history from the same point and the course of life would be very different. Nothing is ordained, least of all the appearance of a clever biped with a capacity to apply sporting metaphors to its own evolution.

Life's Grandeur extends the argument by explaining evolutionary pathways in simple statistical terms. This is a brave move but one that works well for two reasons. In the first place the stats do not ask much of the reader since they involve only the concept of a normal distribution and its skewed right tail. Gould sets out to show that in evolutionary terms these simple distributions can instead be powerful arguments against the idea of evolution as a directed natural process and where variation between individual organisms is mistakenly judged as either progressively better or fixed by some natural law. Excellence, he concludes, is a range of differences not a spot. Averages are an inadequate summary of the variety of life.

The second reason rests with Gould's customary skill in illustrating scientific arguments with brilliantly chosen examples. He shows us how distributions and trends work through two personal concerns: his health and the health of baseball, his sporting passion. He was diagnosed in 1982 as having a rare and invariably fatal form of cancer. His hope for survival sprang from his knowledge of variation within entire populations. He was not a measure of central tendency, a spot on some graph. While half the people with his form of cancer die after eight months, half will live longer. The skewed right tail of the overall distribution means that some must even reach ripe old age. Of course he did not know at diagnosis that he was a right-tailed person but that possibility was a lifebelt.

Death concentrates the mind wonderfully but only baseball statistics can occupy it fully. Gould had survived, but why had baseball hitters with a seasonal average of .400, roughly equivalent to a test average in cricket of over 50, become extinct? The last hitter to better the .400 average was Ted Williams in 1941 and before him seven players managed this feat between 1900 and 1930. All manner of explanations have been forthcoming, as elaborate and predictable as those put forward to explain England's current poor Test match performance.

Gould's answer depends not on character, individual skills, pitches or the number of fixtures but on variation within the entire system being studied. What he shows, using baseball's statistics for batting, pitching and fielding, is that since 1893 when the rules were fixed there has been a general improvement of the game. Paradoxically then, the extinction of the .400 hitter, the pinnacle of personal achievement, is an index of the whole game getting better. What has happened is that the right tail has been pulled in as variation shrinks around a stable mean batting average due to more, better batters.

This time trend in populations is bigger and more important than in baseball. Applied to the evolution of complex biological systems it illustrates Gould's central point that evolution, as Darwin proposed, is a restless opportunistic process: an activity, as Bob Dylan sang (at the same time as baseball's pitching mound was being cut down to size), "with no direction home I like a rolling stone".

Two limiting factors control the behaviour of time trends. The first is the constraint of what is possible, which Gould describes as the right wall to any distribution. To move this wall baseball hitters would have either to evolve a new adaptation or get the rules changed to their advantage. The other limitation is the left wall or point of origin of the population. In the history of life this is where it all began with bacteria and slime molds. There was only one direction in which such systems could go, towards more complex life forms. Direction at this scale is meaningless. Progress, from bacteria to human beings, is an arrogant self-myth. Life's grandeur turns out to be dominated by bacteria, both in terms of numbers and according to his back-of-the-envelope calculations of biomass/weight. It is even possible, using Tom Gold's provocative notion, that life is primarily chemically supplied in the shallow interior of planetary bodies. Life through photosynthesis may be rare and located in the right tail of the entire system. The recent traces of life on Martian meteorites, if verified, might prove Gould right that throughout the universe bacteria are indeed at the modal centre of life's weight and continuity, pressed up against the left wall of variation.

Evolutionary science was invented to explain variation and today there is no more lucid or accomplished exponent of its achievements than Gould. What I took from this book for my own field of human origins was the positioning of the problem of human diversity within life's grand sweep. Because hominid evolution started somewhere out to the right of the bacterial mean it always had the potential for ramifying evolution. Only recently has the flurry of hominid ancestors shown this to be the case, thereby overturning earlier linear models where single ancestors passed the baton to each other in life's great relay race to the present. As always with Gould's books I came away a supercharged Darwinian thankful that someone is tackling the big problems. Except this time he let me down in his final epilogue on human culture.

Here he declares his belief in the elite, the right tail of our current distribution. "So long as the best of us are driven to seek heights of excellence, to stretch the proverbial envelope no matter how little, to regard compromise as beyond contemplation, there is hope for humanity." A belief that comes straight from the 19th century and Prince Ranjitsinhji's cricket book.

Gould has always been at his best when explaining morphology and development. The sticky bits of evolution, the social behaviour that bucks the trend, are not his ground for fighting evolution's corner and this last chapter makes that clear. Perhaps this is because the social lives of snails, Gould's speciality, are stuck on the left wall of minimal complexity. That fact that humans, by contrast, are in the right tail of social diversity allows Gould to prefer the variety of his local restaurant over McDonald's. But he must also recognise his own argument that improvement of the whole system brings consequences, such as the loss of .400 baseball hitting and standard fare rather than escargots.

Clive Gamble is professor of archaeology, University of Southampton.