Y worries

There are two ways to write about a branch of science for an audience of non-scientists; one is to try and make the audience understand the basic principles of the subject, the other is to entertain them by a rapid succession of pieces of information. Steve Jones's latest book falls firmly into the second category. Given that the subject is the biology of the human male, there is of course no shortage of opportunities for amusement as well as instruction. While Jones has many good things to say, he often does not spend long enough over a topic for the reader to get their mind round it. There are also some irritating small errors, such as confusing the 30 Years War with the 100 Years War (p.35), and getting the genders of the French and German words for death wrong (p.260). I also found the frequent straining after jokes annoying. What is the book about? In the preface, Jones refers to Charles Darwin's The Descent of Man and Selection in Relation to Sex, a work which is still well worth reading by anyone interested in the biology of sexual reproduction. Jones's aim is to explore 'many of the questions raised by Darwin' (p.3), and he successfully covers these and more. Chapter 1 starts with some of the basic biology of sexual reproduction, pointing out that the fundamental distinction between the sexes is the numbers and sizes of the gametes they produce (many and small versus few and large). At the chapter's end he writes that this distinction evolved a billion or more years ago, without presenting any evidence. Some ideas on the origins of sex and of eggs and sperm are presented as established facts, when in reality they are among several contested alternatives. In between, he covers the control of sexual development by sex chromosomes, but without explaining the nature of chromosomes, genes or DNA, and without a single diagram. He draws attention to the puzzle of the genetic degeneracy of the Y chromosome, and attributes it to its lack of genetic recombination (p.17). But again, no evidence is described, and the difficult problem of the evolutionary advantage of genetic recombination is dismissed in a couple of paragraphs, before passing on to other subjects. Jones does not discuss why the Y chromosome (largely) fails to recombine with the X, nor does he mention dosage compensation, which is likely to …