Differences between women and men are a source of great fascination to most of us. And, indeed, sex differences are central to our lives. While we may often assume that observed differences between the sexes are, by and large, simply cultural, Bobbi S. Low forcefully challenges this assumption.

If you are interested in learning how sex differences affect our lives, and how our biology and ecology led to these differences, then the revised edition of “Why Sex Matters – A Darwinian Look at Human Behavior” is for you. In this nuanced, wide-ranging survey of evolutionary ecology you will find a wealth of data underscoring the claim that in a world of limited resources, men and women use markedly different strategies to survive and to reproduce. The astonishing message is that these differences persist to be relevant to our lives, even though we seem to have surpassed the mace-swinging brute a long time ago.

Low operates within the paradigm of human behavioral ecology. She seeks to explain human behavior as resulting from an interplay of our biological setup with ecological pressures. At the heart of her strategy lies the tantalizing idea that human behavior, and particularly the oftentimes very apparent behavioral differences between the sexes, can be explained and predicted by studying humans as complex but not qualitatively different animals.

In chapters 1-3, Low explicates the basic arguments and assumptions of (human) behavioral ecology (the phenoytpic gambit, ‘selfish’ genes, kin selection, conflicts of interest, ecological sex differences). Three themes form the core of her book: first, resources are useful in human survival and reproduction. Second, resource uutilization differs for men and women. Third, the differences in between sexes depend not only on genetic but also on environmental differences. Low’s strategy is clear and comprehensible. After explaining the aforementioned basic assumptions, Low moves on by considering how biological sex differences actually play out in various animal species, in primates, as well as in humans (chapters 4-6). Across all species, mice or men, behavioral patterns emerge. Males strive, because more resources, or higher status, correlate with reproductive success. Risky behavior pays for males, because their reproductive success is highly varied and staying safe could mean not to reproduce. Female behavior, on the other hand, is marked by the weighty choice of picking the ‘right’ mate (most of the times: the most resourceful and/or powerful) and on parental effort thereafter.

Next, Low considers how the lives of men and women differed in traditional and transitional societies (chapters 7-8). For example, she wrests plausible confirmations of her assumptions from demographic data from 19-century Sweden. However, she readily admits that “complexity has crept in” in the form of cultural transmission and evolution (p. 135). She thinks that the patterns of behavioral sex differences are influenced, but not fundamentally altered by cultural influences (chapters 9-10). Remarkable examples of this thinking are her analysis of witchcraft trials as a mere elaborate struggle for resources and the claim that all within-sex competition can be viewed as a path to reproductive success. In chapters 11-14, Low evaluates how her theory fares in predicting the lives of contemporary men and women. She shows how patterns of same-sex cooperation differ for men and women and under which conditions cooperation between the sexes seems particularly fraught with tension. Politics, too, is explained as the materialization of a reproductive strategy and Low hypothesizes about the conditions that might attract more women to engage in it. War is a conflict of resources and a playground for men to gain status, not only in small (chapter 13) but also large, complex societies (chapter 14).  Low reserves the final chapter 15 to ask fundamental question about the future of humanity and how our knowledge about sex differences may help to make it a better one.  Low writes of the irony that some of our evolved tendencies, which made us successful in the past, have led to today’s large-scale problems, such as global warming.

So, can we ultimately channel or overcome those evolved tendencies? Will rich and powerful men stop to philander and, on a more serious note, can our species stop competing at an unsustainable pace? Low is “not ready to bet her next paycheck on it” (246).

One may wonder about Low’s pessimism – particularly because Low is eager to emphasize her rejection of genetic determinism. Further, the decade that passed since the original edition has been published revealed much about the (potentially beneficial) workings of cultural evolution, and Low refers to it in quite a few footnotes. It would have been informative if Low would have illuminated the reasons for her pessimism and distinguish it clearly from the, surely unintended, implication that our past foretells our future.

Low has written an accessible, popularized science book on an intriguing and controversial topic. To readers new to the perspective, she offers an expedient and thought-provoking introduction to human behavioral ecology. By providing a wealth of references, a comprehensive glossary, and extensive footnotes, her book should also be helpful for those familiar with the field. Owners of the original edition, however, will find the revisions to be mainly limited to added references related to cultural evolution (mainly chapter 9, to a smaller extend chapters 2 and 10) and to a novel analysis of why ‘tragedies of the commons’ problems arise in some contexts but not in others in chapter 15. In the remaining chapters, Low restricted herself to minor revisions, adding a few recent references here and there. All in all, Low’s book should be of interest to anyone who could benefit from a solid understanding of human nature, like economists, policy makers, and psychologists. Be mindful though that Low’s answers only one kind of ‘why’ question – related to mechanisms that potentially explain statistical significant behavioral differences between the sexes. For your individual life, however, why and how sex matters is, I think, still very much up to you. 

© 2015 Michael Klenk

Michael Klenk, MA Philosophy (UCL), PhD Candidate in Philosophy at Utrecht University, The Netherlands.