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Sex Differences and Sex Roles

The evolutionary perspective on sexual selection makes predictions consistent with observed behavioral and cultural phenomena. Women should prefer higher status mates because such men could better assist them in providing for offspring. Men should prefer women who are somewhat younger than themselves and higher in fertility. Men in all cultures examined to date tend to seek mates near their own age when they are young, yet seek and find progressively younger women as they age. Yet, contrary to socio-cultural power explanations for mate selection criteria, teenage males are attracted to substantially older women (Kenrick & Simpson, 1997).

Sex differences in the division of labor in mating relationships are addressed by adaptionist theory. It is thought that the sexual division of labor during hominid evolution produced the diverging characteristics evident today. The increase in brain size experienced by our ancestors also resulted in a more difficult childbirth due to the enlargement of the skull. In order to compensate for this difficulty, childbirth occurred earlier in development, and human infants were born relatively immature as compared to other animals. While other animals became more and more independent within a matter of months, humans remained dependent on their parents at least until their teenage years (Fisher, 1992). Since women breast-fed infants, they were the likely candidate to care for small children, and became increasingly more burdened by child care as the span of development elongated. This resulted in a division of labor between men and women, with women gathering and performing other tasks close to home, while men hunted for animals and other resources (Buss, 1996). Adaptionist theory produces a portrait of nurturing women and competitive men.

In most species, mating efforts are most likely to be male, parenting efforts female. Mating and parental efforts have different "return curves." Mating effort has a high fixed cost, typically, a male has to establish himself as successful in order to mate. Once a male has been established as a successful resource provider, his fitness in sexual selection multiplies. The return for parental behaviors is more linear to energy expenditure (although in highly polygynous societies, return curves for sons and daughters reflect mating and parenting curves). This dichotomy creates a strong bias in polygynous species such as our own. Because of the higher variability in reproductive success for males, maturation is delayed to achieve larger size and competitive ability. A greater expenditure and risk may be profitable for male mating effort, but not for parental effort (Daly & Wilson, 1996).

Support for the evolutionary origin of sex roles may be seen in the behaviors of our closest relative. We share more than 98% of our genetic material with chimpanzees, in fact they are more closely related to us than they are to any other primate (Diamond, 1992). In a study of chimpanzees in East Africa, McGrew (1981) found that male chimpanzees hunt animals, guard the border of their community territory, and throw more foliage and rocks. Female chimps gather, engage in ant farming and termite dipping three times as often as males (improving their manual dexterity) and engage in more social grooming. Female chimps also spend a lot of time interacting with their young, touching and vocalizing. When male chimps vocalize, they tend to bark, growl, roar, and make strident aggressive sounds. On the other hand, females make more "clear calls," appeals for affiliation. McGrew saw the similarity between chimps and early humans, and believed that these sex roles are responsible for today's sex differences in spatial and verbal skills, as well as intuition, hand-eye coordination and aggressiveness.

Each sex became specialized and more adapted to the types of tasks they performed. The tasks that men performed, such as hunting and defense of territory, are characterized as spatial, silent and aggressive. On the other hand, women verbally interacted with their children and the other women of the group while they foraged for edible plants (McGrew, 1981). The recognized sex differences between men and women support this line of thought. Men excel at certain types of mathematical problems, are generally better at reading maps, solving mazes, and completing other visual-spatial-quantitative tasks such as mental rotations and space relations (Silverman & Eals, 1992). These skills would be useful in navigating about the landscape. On average, men are better at gross motor skills requiring speed and force, from running and jumping to throwing objects (Fisher, 1992).

Women on the other hand, average better "fine" motor coordination, manipulating tiny objects with ease (Fisher, 1992). They are also usually superior at spatial locations and object memory tasks, valuable while searching the underbrush for resources (Silverman & Eals, 1992). Although there is more variation within the sexes than between the sexes in tests of verbal abilities, on average girls; speak sooner, more fluently, with greater grammatical accuracy, and with more words per utterance than boys (Fisher, 1992). A pervading theme of this specialization is the notion that men are socialized in side to side activities, women in more face to face interactions (Buss & Malamuth, 1996).

Carol Gilligan (1982) proposes that women have an outstanding sensitivity for interpersonal relationships, she found that women cast themselves as actors in a web of attachments, affiliations, obligations, and responsibilities to others. Women also seem to have a higher need for affiliation and a longer attention span for conversation. The adaptations to interpersonal situations may make women more sensitive to subtle cues when dealing with others. Women are better at being able to read the emotions contained in facial expressions, even when looking at pictures of people (Pool, 1994). On average, women also read context and all sorts of peripheral non-verbal information more effectively than men (Hall, 1984; McGuinness, 1976).

Gilligan (1982) also suspects differences in the way each gender makes moral judgments, perceive relationships and communicate. She proposes that males make ethical judgments based on an idea of what is right or wrong, while females think about how their actions affect other people and look for options that will result in the best outcome for everyone involved. Men view relationships with other people, particularly males, in terms of hierarchy and always want to know who is on top. Women see relationships in terms of a web, with family, social and emotional ties linking many people in one big network. Females seek to find common ground and rapport with each other, while males tend to complete with and measure themselves against others. Deborah Tannen (1986) concurs that women see communication as establishing connection and intimacy, while men communicate as a way of solving problems and establishing rank and independence. Still, Gilligan holds that the male and female ethics may be opposite, but complimentary, and well-adjusted adults must incorporate both.

In studies of fifth-graders conducted in the 1970's, Lever (1988) found that the style of play and interaction differ between gender. Boys' games are more competitive, have a fixed set of rules, and a predetermined end point where players are divided into and winners and losers. Boys are more likely to play games where participants take different roles (e.g. Pitcher, catcher, batter, etc.), while girls more often chose "single-role play" such as riding bikes or ice skating, where all the players do the same thing. Boys learn to compete with one another, to lead and follow, work together on a team towards a common goal, often in competition with other teams.

While many myths of sex differences in areas such as intelligence, suggestibility, self-esteem, and rote learning versus higher level cognitive processing have been dispelled, differences resulting from adaptation to specific tasks remain (Pool, 1994). Even those who criticize early conceptions of ancient history with fearless, aggressive, and dominant males, and passive, dependent females, do not reject the hypothesis that the sexual division on labor is a likely cause of certain sex-differences (Bleier, 1997).

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