SEX DIFFERENCES are central to our lives, wherever and whenever—however—we live. And we all think about them, from Professor Henry Higgins in My Fair Lady (“Why can’t a woman be more like a man?”) to Sigmund Freud (“What do women want?”) to actor Charles Boyer (“Vive la difference!”).
Are these differences genetically programmed: snakes and snails and puppy-dog tails for boys versus sugar and spice and everything nice for girls? Or are we trapped by our societies into roles that may be uncongenial to us simply because we do, or do not, have a Y chromosome?
This is a fascinating tangle: what do the widely acclaimed (and equally widely denied) differences between men and women mean in terms of the ways in which men and women use resources, take risks, make war, and raise children?
Which differences are lasting, which are ephemeral? If we follow the real differences through time, across space, and into different environments, what might they mean in today’s societies?
We are asking these questions at an exciting time. New research in evolutionary theory, combined with findings from anthropology, psychology, sociology, and economics, supports the perhaps unsettling view that men and women have indeed evolved to behave differently—that, although environmental conditions can exaggerate or minimize these differences in male and female behaviors, under most conditions each scx has been successful as a result of very different behaviors.
I will argue that many apparently complex behaviors and sex differences in fact arise from simple conditions that are conducive to analysis. I begin with the fundamental principle of evolutionary biology, that all living organisms have evolved to seek and use resources to enhance their reproductive success.
They strive for matings, invest in children or help other genetic relatives, and build genetically profitable relationships. In biology, this is not a controversial proposition, and it follows that all organisms will act as though they are able to calculate costs and benefits.
Futhermore, in biological terms the currencies are, in the end, reproductive: that is, who survives and who reproduces best? This principle seems so simple that it is hard to imagine that diverse and complicated behaviors could arise from it. Vet they do, because the ecological conditions that shape success vary so widely.
There is growing evidence that humans are not immune from this principle, for in order to survive and persist, we humans must solve the same ecological problems as all other species. Evolutionists argue, therefore, that people have evolved to behave in ways that do, or did, contribute to their reproductive success.
This approach can help us answer apparently diverse, unconnected questions such as the following: Why are there so few women warriors? Why were chastity belts designed for women, not men?
Why aren’t old women seen as sexy, but old men often are? Wiry are practices such as infanticide routine in some cultures and forbidden in others? Many of these questions can be posed only by using an evolutionary approach; in other approaches they have represented problems, or “noise.”
I present three themes in this work. First, resources are useful in human survival and reproduction; like other living things, we have evolved to wrest resources from the environment for our benefit. Second, the two scxes tend to differ in how they can use resources most effectively to accomplish survival and reproduction.
Third, how each scx accomplishes these ends relies not only (and not obviously) on differences in genes, but on differences in environment— there are no identified genes specific for polygyny, for example, but in many environments the trends for male mammals to profit from trying to be polygynous are strong.
These intertwined motifs of resource utility, sex differences, and environmental constraints soon lead us to consider other problems— for example, status striving and risk taking. Why is homicide largely a male enterprise?
Why are men and women jealous about different things? Differences such as these give rise to the grander issues of population numbers, resource consumption, and sustainability. As human populations have grown and technologies have become more efficient, the utility of resources in simple survival and reproduction leads us to a series of dilemmas: Why did family sizes fall in nineteenth-century Europe and North America (the “demographic transition”)?
Why is today’s demographic transition in the developing world so different? What is the impact of the “global village”—the evolutionary novelty that our actions here and now affect others’ lives far away?
What can we do about the fact that many of today’s problems have relatively straightforward technical solutions— which will work only if we can see the interests of strangers in strange lands as equal to our own, something it never paid our ancestors to do?