Sociobiologists apply evolutionary biology to understanding the causes of human social behavior. The sociobiological approach to human sexuality has been articulated particularly by Symons (1979, 1987; see also Barash, 1977; Buss & Schmitt, 1993). The bottom line in understanding any social behavior, according to sociobiologists, is reproductive success, that is maximizing the number of genes one passes on to the next generations. Therefore, patterns of human sexual behavior should be powerfully shaped by their implications for reproductive success.
Sociobiologists have proposed two reasons for the existence of the double standard—society’s permissive attitudes toward male promiscuity and intolerance for female promiscuity. First, they point out that sperm are plentiful (the human male manufactures millions per day), whereas the egg is comparatively rare (only one egg is produced per month) and is therefore precious. Thus, it makes evolutionary sense for the male to inseminate many females but for the female to be selective about which genes are paired with hers in the rare egg. Second, they point out that the woman commits nine months of her body’s energy to gestation. Therefore, at birth her parental investment exceeds the man’s considerably (Trivers, 1972). Greater parental investment fosters greater parental investment. Having already invested more, it is to the woman’s advantage to continue caring for the young once they are bom so that they survive into adulthood and pass on her genes to the next generation. She is also likely to prefer a mate who is willing and able to provide resources that will ensure that the offspring will be adequately cared for (Buss, 1989).
The predictions from sociobiology regarding gender differences in sexual behavior, then, are clear: Men should be more interested in and approving of casual sex and should have a larger number of different sexual partners, whereas women should be less interested in and approving of casual sex and should have a smaller number of different partners.
More recently, a second generation of sociobiologists, preferring to call themselves evolutionary psychologists, has emerged (e. g., Buss &. Schmitt, 1993). In response to the criticism that much of sociobiology consists of post hoc explanations of phenomena, evolutionary psychologists have made efforts to frame hypotheses in advance and then test them with data.
Buss and Schmitt’s (1993) sexual strategies theory is an example. They make a distinction between short-term mating strategies (e. g., casual sex) and long-term mating strategies (e. g., marriage). They argue that men and women have different sexual strategies (i. e., strategies to maximize reproductive success) in these two different contexts. Buss and Schmitt then frame a number of hypotheses based on this analysis, including the following:
1. Because of differences between women and men in parental investment, men devote a larger proportion of their total matings to short-term matings than women do.
2. Men’s short-term mating strategies are influenced by a need to identify which women are fertile. Men generally use youth and physical attractiveness as indicators.
3. Women’s long-term mating strategies are influenced by a
need to identify men who have both the ability and willingness to invest resources in her and her children on a longterm basis.
Thus Buss and Schmitt arrive at the same predictions as the older sociobiologists, namely that men are more interested in and approving of casual sex than women. Their theorizing also leads to specific predictions about mate selection, which we discuss in a later section.
Feminist criticisms of sociobiology are numerous (see, e. g., Hrdy, 1981; Janson-Smith, 1980; Travis & Yeager, 1991; Weisstein, 1982). Feminists are concerned that sociobiology can become a rationale for the status quo. If men have been selected for greater aggressiveness, for example, one might conclude that woman battering is genetically based and cannot be changed. Moreover, sociobiology has been criticized for resting on an outmoded version of evolutionary theory that modern biologists consider naive (Gould, 1987). For example, sociobiology has focused mainly on the individual’s struggle to survive and pass on genes to the next generation, whereas modern biologists focus on more complex issues such as the survival of the group and the species, and the evolution of a successful adaptation between the species and its environment.