Given humans’ close biological relationship to primates, one might expect to see similar dynamics of sex and gender between human and nonhuman primate social groups. Biologists and primatologists have examined sex differences in the biology and behavior of both nonhuman and human primates, looking for commonalities that might suggest a common biological genesis for sex/gender categories.
Primate Sex Differences: Biology and Behavior
In the 1950s, a time when American men were supposed to be breadwinners and American women were urged to be housewives and mothers, most primatologists believed that males were the public actors in primate social life, while females were passive, marginal figures. Primatologists of the time believed that males constantly competed against one another for dominance in a rigid group hierarchy, while females were more narrowly interested in raising young (Fedigan and Fedigan 1989). In fact, primatologists described the total social organization of primates in terms of male competition. This view went along with Charles Darwin’s notion that males are forced to compete for the opportunity to mate with females and so, therefore, must be assertive and dominant. Females, in Darwin’s theory, were shaped by evolution to choose the strongest male to mate with and then concern themselves exclusively with nurturing their offspring to adulthood.
By the 1980s, however, a number of strong studies were showing some very surprising things about primate social organization. First, most primate groups are essentially composed of related females, with males as temporary members who often move between groups. The heart of primate society, then, is not a set of competitive males but a set of closely bonded mothers and their young. Females are not marginal figures but central actors in most social life. The glue that holds most primate groups together is not male competition but female kinship and solidarity.
Second, social organization in primates turned out to be incredibly complex, with both males and females actively strategizing for desirable resources, roles, and relationships. Research on a number of primate species has demonstrated that females are often sexually assertive and highly competitive. Female primates actively exercise their preference to mate with certain male “friends” rather than aggressive or dominant males. For males, friendliness with females may be a much better reproductive strategy than fighting with other males. Moreover, many primatologists have begun to identify cooperation rather than competition as the central feature of primate social life while still recognizing competition for resources by both males and females in their pursuit of survival and reproduction (Fedigan and Fedigan 1989).
What this means, in a nutshell, is that (1) both females and males are competitive, (2) both females and males are cooperative, and (3) both females and males are central actors in primate social life.
While evidence suggests that in primate groups males and females are equally important to social life, this still leaves open the question of biological differences and their link to behavioral differences. The anatomy of primate males and females differs in two main respects. First, of course, adult females can and often do experience pregnancy and bear offspring. The females of most primate species are often pregnant or nursing for most of their adult lives and devote more time and resources to care of young than males do (although there are some notable exceptions, such as certain species of New World monkeys). And some researchers have noted the tendency of juvenile females to pay more attention to primate babies in the group than do juvenile males.
Second, male primates tend to be slightly bigger than females, although this difference itself is quite variable. The size difference between males and females of any species is referred to as sexual dimorphism. Male and female gibbons are nearly the same size, while male gorillas are nearly twice the size of females. Female chimpanzees are about 75 percent the size of males. Human females are about 90 percent the size of males, making human sexual dimorphism closer to gibbons than chimpanzees.
Some researchers suggest that a high level of sexual dimorphism is associated with strong male dominance, rigid hierarchy, and male competition for mating with females. Certainly these features reinforce one another in gorilla society. A low level of sexual dimorphism may be associated with long-term monogamy, as with gibbons. However, anthropologist Adrienne Zihlman cautions against making any firm judgments about the relationship between biological features such as size and behavioral features such as sexual relations. She remarks, “There is no simple correlation between anatomy and behavioral expression, within or between species” (1997, 100). Reviewing research on sex differences in gibbons, chimpanzees, gorillas, and orangutans, she concludes that each species features a unique “mosaic” of sex differences involving anatomy and behavior, with no clear commonality that might predict what is “natural” for humans.
Humans’ closest primate relatives are chimpanzees and bonobos, both sharing 99 percent of their DNA with humans, and yet each species exhibits very different gender-related behaviors. Bonobos are female-dominant, while chimpanzees are male-dominant. Bonobo groups are mostly egalitarian and peaceful, while chimpanzee groups are intensely hierarchical, with frequent male aggression between groups. Sexual behavior among bonobos is remarkably frequent and extraordinarily variable, with a wide range of same-sex and opposite-sex pairings involving various forms of genital contact. Some researchers believe that sexual contact helps build social bonds and ease conflicts in bonobo groups. Bonobos have been called the “make love, not war” primate. Sexual behavior among chimpanzees is also variable but much more limited to opposite-sex pairings. A female in estrus may mate with several males, a pattern called opportunistic mating. Short-term exclusive relationships may form, in which a male guards a female to prevent other males from mating with her. Consortships also happen, in which a female and a male leave the group for a week or more.
With such variability between humanity’s two closest DNA relatives, it is impossible to use nonhuman primate behavior to make assumptions about what is “natural” for human males and females. In fact, with regard to gender, the lessons of primatology may be that apes (like humans) are biologically quite flexible and capable of many social expressions of gender and sexuality.
Human Sex Differences: Biology and Behavior
Just as with primate research, research on human biological sex/gender differences has been considerably slanted by the gender bias of the (often male) researchers. Within the Euro-American intellectual tradition, scholars in the past have argued that women’s biological constitution makes them unfit to vote, go to college, compete in the job market, or hold political office. More recently, beliefs about the different cognitive abilities of men and women have become widespread. Males are supposedly better at math and spatial relationships, while females are better at language skills. Hormonal activities supposedly make males more aggressive and females more emotional.
In her book Myths of Gender, biologist Anne Fausto-Sterling (1992) conducts a massive review of research on cognitive and behavioral sex/gender differences in humans. Looking very closely at the data, she finds that the vast number of studies show no statistically significant difference whatsoever between the cognitive abilities of boys and girls. A minority of studies found very small differences. For instance, among four studies of abstract reasoning abilities, one study indicated that females were superior in this skill, one study indicated that males were superior, and two studies showed no difference at all. Overall, when differences are found in verbal abilities, girls usually come out ahead, but the difference is so small as to be irrelevant to questions of education and employment. Likewise, more than half of all studies on spatial abilities find no difference between girls and boys. When differences are found, boys come out ahead, but the difference is again very small. Looking at the overall variation of skill levels in this area, only about 5 percent of it can be attributed to gender. This means that 95 percent of the differences are due to other factors, such as educational opportunities.
Even these tiny differences that may exist in the cognitive talents of different genders are not necessarily rooted in biological sex differences. Several studies of spatial abilities have shown that boys may initially perform better on spatial ability tests, but when given time to practice, girls increase their skill levels to become equal to boys, while boys remain the same. Some researchers reason that styles of play such as sports, often encouraged more by parents of boys, may build children’s spatial skills. Parenting styles, forms of play, and gender roles—all elements of culture—may shape the data more than biology. Cross-cultural studies also indicate that culture plays an important role in shaping abilities. A study of the Inuit found no differences at all in the spatial abilities of boys and girls, while in a study of the Temne of Sierra Leone, boys outperformed the girls. Inuit girls are generally allowed more freedom and autonomy, while Temne girls are more restricted in their activities.
Similar complexities emerge in the analysis of studies on aggression. Fausto-Sterling found that most studies revealed no clear relationship between testosterone levels and levels of aggression in males. Moreover, testosterone aggression studies have been riddled with problems such as poor methodology, questionable definitions of aggression, and an inability to prove whether testosterone provokes aggression or the other way around. Where differences in aggression between girls and boys are documented, some researchers have concluded that cultural factors may play a strong role in producing those differences. Anthropologist Carol Ember studied levels of aggression among boys and girls in a village in Kenya. Overall, the boys exhibited more aggressive behavior, but there were exceptions. In families lacking girl children, boys were made to perform more “feminine” work such as childcare, housework, and fetching water. Boys who regularly performed those tasks exhibited less aggression than other boys—up to 60 percent less for boys who performed a lot of this work.
As with the primate research on sex differences, research on the brains, bodies, and behaviors of male and female humans does not seem to suggest that significant behavioral differences are biologically hardwired. While researchers have discovered differences in the cognitive talents and social behaviors of males and females, those differences are very small and could very well be due to social and cultural factors rather than biology. As with bonobos and chimpanzees, humans are biologically quite flexible, allowing for a diverse array of forms of gender and sexuality.
The content of this course has been taken from the free Anthropology textbook by Openstax