How Sex Works, in a nutshell, is a whirligig tour of the biology of human sexuality given by New York Times best-selling author Sharon Moalem. Like many other pop science titles, Moalem aims to deliver a torrent of factual trivia in a readable and entertaining manner. Given the somewhat taboo overtones such a subject often encounters in some quarters of society, Moalem’s light-hearted prose combined with his medical expertise does much to make his treatment of the topic devoid of much if any moral, ideological or political flashpoints — though the author does provide his moral two cents from time to time (e.g. condemning female genital mutilation). Given this rather uncontroversial tenor to the book, however, those looking for a more polemical or risqué canvassing of the topic are perhaps better suited looking elsewhere.

Though Moalem’s book certainly may strike readers at times as a redux of their high school sex ed. class, his integration of recent medical discoveries adds tremendous value to the topics covered. For instance, Moalem discusses some recent literature on the human leukocyte system (HLA) — otherwise known as the major histocompatibility complex (MHC) — to help shed light on the issue of human pheromones (or lack thereof). It should also be pointed out that the author does not shy away from discussing the evolutionary significance of many of the phenomena covered. In this vein, Moalem cites the work of others who tie in talk of pheromones as an indicator of underlying MHC genes, the latter of which are taken to be a critical criterion of mate choice among humans, with dissimilar MHC’s between mates being preferred. It is this steadfast application of Darwinian insight that often sets the book apart from what would otherwise be a rather straightforward, textbook-like — and perhaps even dated — treatment of the biology of sex.  

As an example of Moalem’s bringing to bear of recent research to the numerous topics covered throughout, chapter 4 discusses analogs of the sexual behavior of men with monogamous and polygamous male prairie voles and montane voles, respectively. He cites a 2008 study by behavioral geneticist Hasse Walum in the journal Proceedings of the National Academy of Sciences which found that married men homozygous at a specific chromosomal locus, with two copies of the allele RS3 334, had twice the rate of marital dysfunction, broadly construed, than those with one or none of the alleles. This is but one instance in the book where Moalem attempts to dissolve fascinating yet provocative issues with the latest empirical findings.

It should be stressed that, indeed, Moalem leaves no anatomical crevices or biological substrates related to sex unexplored in the book. On the female side, topics range from the G-spot to female ejaculation to a brief consideration of the evolutionary function of the female orgasm; and on the male side, from prostatic fluid to circumcision to the zinc-rich composition of sperm.

Chatper 5 discusses the evolution of sex itself and sexual development disorders. Moalem provides a broad outline of the ‘Red Queen’ view of sexual reproduction — a term first coined by evolutionary biologist Leigh Van Valen after Lewis Carroll’s Through the Looking Glass, and later popularized by Matt Ridley in The Red Queen. From here Moalem takes readers through a survey of disorders of sexual development (DSD) ranging from congenital adrenal hyperplasia, Klinefelter syndrome, and androgen insensitivity syndrome (AIS). Moalem does a good job of showing how genetic, hormonal and environmental factors can conspire in making quick ascriptions of sex and gender problematic. Scattered throughout this discussion are well-chosen anecdotal cases for thought-provoking illustration.

In Chapter 6, Moalem shifts his focus to homosexuality. After highlighting its rampant occurrence across the animal kingdom — in literally hundreds of species — the author reports the view of homosexuality postulated by scientists like Joan Roughgarden and Robin Dunbar as a bonding mechanism among herd and social animals. The discussion quickly turns to homosexuality in humans, where Moalem conducts an in-depth look at the recent work of Andrea Camperio-Ciani, who has found higher reproductive rates in the maternal female relatives of gay men vis-à-vis that of female relatives of straight men. However, Moalem is sure to remind readers that those who propound such genetic based explanations of homosexuality are not at the same time denying the importance of an environmental interaction. Moalem closes out the book with chapters on STD’s and contraceptives, both of which are practically informative.

If there are two (minor) shortcomings to the book, they are the following. Firstly, many of the references cited by Moalem are from stories and science reporting in the popular press. It would’ve been preferable to have the entirety of the references in the book drawn directly from the peer-reviewed scientific literature, since the inclusion of material from media sources weakens the credibility of those points they’re intended to buttress. Secondly, given the remarkable efflorescence of sex and mating-related work done in evolutionary psychology over the last two decades, it would’ve been especially beneficial if the book delved into the literature somewhat more. But these minor cavils aside, Moalem’s book provides a solid, clear and up-to-date account of the biology of sex. And though the book can come across at times as reminiscent to standard textbook fare, what would otherwise be a drab lesson in anatomy and physiology is on the whole enlivened by Moalem’s laid-back and engaging style.  

© 2009 John Klasios

John Klasios, York University, Toronto.