Sexual division of labour

Overview

The Sexual Division of Labor (SDL) is defined as the delegation of different tasks between males and females. Among human foragers, males and females target different types of foods and share them with each other for a mutual or familial benefit. In some species, males and females eat slightly different foods, while in other species, males and females will routinely share food-but only in humans are these two attributes combined. The few remaining hunter-gatherer populations in the world serve as evolutionary models that can help explain the origin of the sexual division of labor. Many studies on the sexual division of labor have been conducted on hunter-gatherer populations, such as the Hadza-a hunter-gatherer population of Tanzania.

Behavioral Ecological Perspective

Man the Hunter vs. Woman the Gatherer

Both men and women have the option of investing resources either to provision children or to have additional offspring based on life history theory. Males and females monitor costs and benefits of each alternative to maximize reproductive fitness; however, trade-off differences do exist between sexes. Females are likely to benefit most from parental effort because they are certain which offspring are theirs and have relatively few reproductive opportunities, each of which is relatively costly and risky. In contrast, males do not have an absolute certainty of paternity, but may have many more mating opportunities bearing relatively low costs and risks. Though not every hunter-gatherer population pinpoints females to gathering and males to hunting, the norm of current and ancestral populations divides the roles of labor in this manner. Natural selection is more likely to favor male reproductive strategies that stress mating effort and female strategies that emphasize parental investment. As a result, women have been relegated to the low-risk task of gathering vegetation and underground storage organs that are rich in energy to provide for themselves and offspring. Since women provide a reliable source of caloric intake, men are able to afford a higher risk of failure by hunting animals.

Hypotheses for the Evolutionary Origins of SDL

Traditional Hypothesis

Provisioning Household

The traditional explanation of the sexual division of labor finds that males and females cooperate within pair bonds by targeting different foods so that everyone in the household benefits. Females may target foods that do not conflict with reproduction and child care, while males will target foods that females do not gather, which will reduce variance in daily consumption and provide a broader diet for the family. Foraging specialization in particular food groups should increase skill level and thus foraging success rates for targeted foods.

Alternative Hypotheses

“Show-Off” / Signaling Hypothesis

The “show‐off” hypothesis proposes that men hunt to gain social attention and mating benefits by widely sharing game. This model proposes that hunting functions mainly to provide an honest signal of the underlying genetic quality of hunters, which later yields a mating advantage or social deference. Females tend to target the foods that are most reliable, while men tend to target difficult-to-acquire foods to “signal” their abilities and genetic quality. Hunting is thus viewed as a form of mating or male-male status competition, not familial provisioning. Recent studies on the Hadza have revealed that men hunt mainly to distribute food to their own families rather than sharing with other members of the community. This conclusion suggests evidence against hunting for signaling purposes.

SDL and Optimal Foraging Theory

Optimal Foraging Theory (OFO) states that organisms forage in such a way as to maximize their energy intake per unit time. In other words, animals behave in such a way as to find, capture, and consume food containing the most calories while expending the least amount of time possible in doing so. The sexual division of labor provides an appropriate explanation as to why males forgo the opportunity to gather any items with caloric value- a strategy that would seem suboptimal from an energetic standpoint. The OFO suggests that the sexual division of labor is an adaptation that benefits the household; thus, foraging behavior of males will appear optimal at the level of the family. If a hunter-gatherer man does not rely on resources from others and passes up a food item with caloric value, it can be assumed that he is foraging at an optimal level. But, if he passes up the opportunity because it is a food that women routinely gather, then as long as men and women share their spoils, it will be optimal for men to forgo the collection and continue searching for different resources to complement the resources gathered by women.

Cooking and the Sexual Division of Labor

The emergence of cooking in early Homo may have created problems of food theft from women while food was being cooked. As a result, females would recruit male partners to protect them and their resources from others. This concept, known as the theft hypothesis, accommodates an explanation as to why the labor of cooking is strongly associated with the status of women. Women are forced to gather and cook foods because, otherwise, they will not acquire food otherwise and access to resources is critical for their reproductive success. On the contrary, men do not gather because their physical dominance allows them to scrounge cooked foods from women. Thus, women’s foraging and food preparation efforts allow men to participate in the high-risk, high-reward activities of hunting. Females, in turn, become increasingly sexually attractive as a means to exploit male interest in investing in her protection.

Sexual Division of Labor and the Evolution of Sex Differences

Recent studies have found that males are better at tasks that involve spatial ability, while females have an advantage in object memory tasks. The sexual division of labor provides an ultimate explanation for these cognitive differences. Hunting requires travel over a wide territory with much solitary scouting and reconnoitering. Males needed the ability to follow prey over long distances and to accurately target their game with projectile technology. As a result, male specialization in hunting prowess would have spurred the selection for increased spatial and navigational ability. Gathering, on the contrary, necessitates behaviors of continual social interaction and object location memory. The ability of women to remember the locations of underground storage organs and other vegetation would have led to an increase in overall efficiency and decrease in total energy expenditure since the time spent digging for food would decrease. Selection on behaviors that increase hunting success and energetic efficiency would bear a positive influence on reproductive success. Thus, the different tasks required in the division of labor between males and females provide an ultimate explanation for the sexually dimorphic behaviors of cognition that exist today.

Significance: Why the Sexual Division of Labor?

Evolutionary Perspective

Based on the current theories and research on the sexual division of labor, four critical aspects of hunter‐gatherer socioecology led to the evolutionary origin of the SDL in humans: (1) long‐term dependency on high‐cost offspring, (2) optimal dietary mix of mutually exclusive foods, (3) efficient foraging based on specialized skill, and (4) sex‐differentiated comparative advantage in tasks. These combined conditions are rare in nonhuman vertebrates but common to currently-existing populations of human foragers, which, thus, gives rise to a potential factor for the evolutionary divergence of social behaviors in Homo.

External links

• Hunter-Gatherer
• Division of Labor
• Evolution
• Adaptation
• Natural Selection