(p. 313) Mating, Reproduction and Life History
The study of mate preferences and reproductive decision-making are the areas that have, perhaps inevitably, seen the greatest concentration of studies in human evolutionary psychology hitherto. Evolution is all about reproduction, so the means by which individuals select their mates, and the investment decisions they make with respect to offspring, are the obvious evolutionary questions to ask when considering humans in this light.
The first wave of studies in this area established that, like many other animal species, human females' reproductive success rests on access to resources while that of males depends more on access to mates, and that perceptions of attractiveness and mate preferences are consistent with such findings. With time, however, it has become apparent that the picture is much more complex and culturally driven than we suppose. Campbell's consideration of sex differences in aggression is a case in point: sex differences are apparent, but this doesn't translate into a simple dichotomy of aggressive males and peaceful females. The sexes differ both in the amount and kind of aggression they use, so that, while these can be tied to reproductive strategies, doing so requires a more nuanced interpretation, and a consideration of many different levels of explanation. The qualitative differences in aggression are more interesting, and more evolutionarily relevant, than the well-established quantitative difference that has tended to be the focus of research to date. This is not to say that these strategic sex differences do not exist, but rather to point out, as Voland does, that it is the way these strategic predispositions are fined-tuned to circumstance that makes human behaviour both particularly complex and particularly interesting from an evolutionary perspective.
One thing that makes humans particularly intriguing animals to study is their peculiar life history. This has major implications for the kinds of evolutionary predictions one will make, as Lummaa illustrates. The complete helplessness of human infants means that females require assistance in the raising of offspring, and that males may have been selected to invest more in offspring and less in mating opportunities than is often assumed. The role of kin, particularly grandmothers, in raising offspring successfully is also becoming increasingly prominent, with implications for human life-history evolution. Moreover, as Mace notes, the idea that maximizing the number of surviving offspring is the key to high fitness is also less secure for humans than for other species, due to resource transfers that can occur after the death of parents, and because factors promoting lineage survival in the long term may not be those that promote high reproductive output in the short term. However, we currently know very little about the psychological motivations that underlie reproductive decision-making. While Mace, Voland and Winterhalder all consider the (p. 314) kinds of psychological mechanisms that underlie peoples' reproductive decision-making, and come up with some fascinating suggestions that show clear links to work on cultural evolution, it is also clear that more empirical work is sorely needed.
Mate preferences may also be more complex than originally assumed. Gangestad as well as Rhodes and Simmons provide critical reviews of the corpus of research on mate choice preferences, illustrating the methodological rigour that such studies require, as well as highlighting the need for more detailed, multi-dimensional studies of mate preferences, which would allow the potential synergies between different cues and signals of mate quality to emerge. The pressing need to tie mate preferences to real-life mating decisions is another area where further empirical data would be valuable. Despite the plethora of publications, it is apparent that there is still a lot of mileage in the study of human mate choice, especially given that, as Wedekind indicates, we may have neglected the role played by other sensory modalities.