There are 35 species of wild dog, but only one domesticated species, descended from the wolf. Yet the degree of variation within the domesticated species transcends that in all its wild relatives put together. Chihuahuas stand six inches tall at the shoulder, Irish wolfhounds four feet. A St Bernard weighs 50 times as much as a Pomeranian. This variety has been produced by artificial, not natural, selection. But, in principle, conscious selection to satisfy human whim is little different to blind selection to ensure survival in nature. Both demonstrate that variation within an existing form can bring forth new kinds of creatures quite different from their ancestors.
Almost Like a Whale is an updating of On the Origin of Species. (Darwin, in fact, opened The Origin with a discussion not of dogs but of pigeons.) To rewrite what Jones acknowledges as "the book of the millennium" requires considerable skill, bravado and, possibly, a touch of madness. Jones clearly has more than his fair share of all three: this is a delightful book, infused with wit and panache, and as enthralling in its own way as was Darwin's original. Jones has kept to the structure of On the Origin of Species; both the chapters and many of the chapter sections are the same as in the original. But he has torn out the book's innards and rewritten it from scratch. From Aids to wine growing, from embryology to ecology, Jones casts a contemporary eye over a century-old theory.
Of all the great Victorian texts that have shaped the 20th century's understanding of the world - such as Marx's Das Kapital and Freud's Interpretation of Dreams - no book lends itself better to Jones's treatment than The Origin. Unlike those of Marx or Freud, Darwin's theory remains intact. At the same time, a century of scientific advance has accumulated the kinds of evidence for evolution by natural selection that simply were not available to Darwin himself. The result is that Jones has been able both to be faithful to Darwin and to write an entirely new work. As he himself puts it, "Almost Like a Whale tries to read Charles Darwin's mind with the benefit of scientific hindsight". It is vision wonderfully conceived and gloriously executed. At the end of each chapter Jones has appended Darwin's original summaries from The Origin; it is a measure of how beautifully poised is Jones's own writing that Darwin's words seem not to be out of place at all.
The biggest transformation in evolutionary theory over the past century has come from the emergence of genetics as a science. In Darwin's day no one had a clear idea about how an organism inherited its characteristics from its parents. The dominant notion was that of "blending": the belief that the characteristics of the parents merged to create intermediate traits in the offspring. This, however, posed a tremendous quandary for Darwin. His theory relied on the existence of variation within a population: only if there are sufficient differences between organisms could nature select from among them. But the idea of blending suggested that such differences got erased and that within a few generations a species would be uniform in its character. Darwin's inability to explain the origin and maintenance of variation was a key weapon for opponents of evolution.
We now know that inherited characters do not blend together but are inherited as discrete particles - as genes. The idea of particulate inheritance was first proposed by the Austrian monk Gregor Mendel in the 1860s. His work was initially ignored - an uncut copy of Mendel's paper was found in Darwin's library after his death. Mendel's work was rediscovered only in the early years of this century. It was another three decades before Mendelian genetics and Darwinian theory fused to create the "Modern Synthesis". But once the synthesis was created, it transformed our understanding of evolutionary theory and ensured that evolution became the central theme of biological thought. Almost Like a Whale provides a barnstorming tour of modern genetics and its implications for evolutionary theory.
The second big input into Darwinian theory this century has come from sociobiology. For Darwin, natural selection acted solely upon the individual. Those better suited to a particular environment survived and reproduced, and passed on their characteristics to future generations. The characteristics of the less fit were confined to the evolutionary graveyard. Translated into the genetic level this is the idea of the "selfish gene". Such a view of evolution posed a problem, however: how does natural selection create altruistic traits? By definition, altruism - an act that benefits another at some cost to yourself - makes you less fit, and hence should be selected against. It was a problem that troubled biologists from Darwin onwards.
Many biologists were led to argue that natural selection acted not on the individual but on populations, and worked for the good of the group, not the individual. This idea was decisively undermined in the 1960s. The British biologist Bill Hamilton introduced the idea of "kin selection" to explain altruistic behaviours. You share many of your genes with your relatives. Therefore you can influence the course of evolution not just by passing on your genes but also by helping your relatives to pass on theirs. Altruism grows out of selfishness. Hamilton took these ideas and gave them a precise mathematical formulation. His work, and that of fellow thinkers such as Robert Trivers, George Williams and John Maynard Smith helped launch the sociobiological revolution of the 1960s and 1970s.
Jones makes full use of these ideas to extend the argument of On the Origin of Species. He is highly critical, however, of the attempt to apply sociobiology to any manner of human behaviours. It is not that Jones thinks that humans stand outside evolution - far from it. The one new chapter in Almost Like a Whale is on human evolution. In The Origin, Darwin tactfully skirted round the question of human evolution. "I think I shall avoid the whole subject," he told a colleague, "as so surrounded by prejudice; though I fully admit that it is the highest and most interesting problem for the naturalist." Jones therefore inserts a short chapter on human evolution, the evidence for it and its impact on our lives. He denies, however, the possibility of understanding humans in the same terms as we can understand other animals. Human culture transforms human behaviour so much faster than can natural selection that evolution "is beside the point". He derides as "vulgar Darwinism" the "attempts to explain the oddities of human life - sex life included - in terms of that of bees or chimpanzees". Evolution, he observes, "is to the social sciences as statues are to birds: a convenient platform upon which to deposit badly digested ideas". Darwin, he points out, deserves better than this.
Almost Like a Whale demonstrates how robust is Darwin's theory, and how able it is to carry the weight of a century and a half of scientific research. The book, however, does tend to flatten the debates among Darwinians themselves. When Darwin wrote The Origin, the main debate was between those who accepted the idea of evolution by natural selection and those who believed the species were created through divine intervention. Today - the millions of American who claim to believe the literal word of Genesis notwithstanding - the real arguments are between Darwinists of various strands. Is evolution a gradual process or does it move in fits and starts, as the American palaeontologist Stephen Jay Gould claims? To what extent are the characteristics of animals designed by natural selection and to what extent are they accidental? Does natural selection operate at the level of the gene, the individual or the population? How are we to understand the impact of evolution on humans? Jones refers to many of these debates but, inevitably, is forced to ignore their nuances.
"I have never met a biology undergraduate who has read On the Origin of Species," Jones writes. The irony is that his future students will probably be more familiar with Almost Like a Whale than with On the Origin of Species. But then Jones's updating of Darwin's masterpiece is itself a splendid metaphor for evolution. What better illustration could there be of Darwin's central idea of descent with modification?