The dramatic physical changes our ancestors experienced also triggered equally significant social changes that led to the evolution of the most basic social unit of our species: the family. One likely scenario involved two lines of development converging to create the family. First, as our ancestors moved out of the trees into the savannah in search of grains and grasses, they occasionally came across a carcass that they would pick clean for the meat. This casual scavenging gave them a taste for meat that developed into more intentional hunting. With the females tied down by the children, the males were generally the only ones free to hunt. Meanwhile the females and children would gather edible plants. Most likely, hunting was rarely successful, providing only about 10-20% of the food our ancestors ate, although the meat did provide valuable protein. The need to supplement the usually meager returns on their hunting may give us another clue as to why the males kept returning to the rest of the group. This pattern of food sharing created bonds vital to the evolution of the family.
Another development had to do with the evolution of a large brain and head which made the birthing process for humans more difficult. As a result, nature compensated by having human babies come to full term prematurely, making them among the most helpless animals at birth in all of nature. This greatly increased and prolonged children’s dependence on their mothers, who in turn needed protection and help getting food, especially in the harsh environment of the savannah.
The question is: why did males keep returning to the females and children? According to one theory, the answer lies in the evolution of year round mating in females to replace the seasonal estrus cycle that occurs in most mammals. The females who developed this pattern (by a purely random mutation) were better able to attract males to help them with food gathering and protection. As a result, more of their children survived to pass this characteristic on to future generations until it became the prevailing trait in humans.
Over time, these factors (year-round mating and food sharing) created permanent bonds that we have come to know as the family. Strengthening these bonds were two other factors. One was the added companionship and security of family life. We know, for example, that our prehistoric ancestors would feed and care for crippled members of their group despite their inability to contribute significantly to everyone else’s survival. Secondly, there was the emotional satisfaction that children gave their parents in terms of companionship, care in old age, and as an extension of themselves.
For centuries there has been a controversy over the source of differences in male and female behavior and values within our species. Oftentimes described as the “Nature vs. Nurture” debate, it focuses on whether differences between men and women are the result of genetic or environmental factors. Coming largely from the Women’s Movement in the 1970s, the pendulum swung heavily to the side of nurture, the assumption being that aggressive tendencies in boys were the result of cultural factors and upbringing. The hope and belief was that if boys could be raised in an environment that didn’t stress aggression and violence, they would be no more aggressive than girls. Unfortunately, more recent research shows things are not quite that simple. While the environment is important in determining the way aggression is channeled, there are also inherent genetic factors influencing the equation. Testosterone levels in an individual are one factor. How men and women’s brains are structured is another. This may be the result of the hunting and gathering lifestyle our ancestors followed for the vast majority of our species’ existence and the different roles men and women played in it.
For men, who typically did the hunting, stalking and waiting for game required two main mental abilities: staying focused on one goal for long periods of time and keeping quiet during that prolonged period of waiting. This discouraged verbal socializing that could scare off any game. Nature would favor males whose brains were adapted to these qualities by awarding them successful hunts while killing off the more chatty ones through unsuccessful hunting and starvation.
Women, who performed very different tasks, required very different qualities. While looking for and gathering any edible vegetation, they also might have to keep track of several children and look out for predators. Unlike men, who had to stay quiet, those women who cooperated with one another (especially in looking out for one another’s children) and communicated verbally would be much more successful than women who operated quietly and independently of one another. For one thing, the sound of a number of women talking might be enough to scare off some potential predators. Such cooperation and communication would also create strong social bonds between the women, providing much of the glue that has kept societies together down through the ages. And just as nature would favor men with brains adapted to focus quietly on one goal, it would favor women whose brains were more adapted to verbal socializing and keeping track of several things at once.
Indeed, recent research has shown that men and women’s brains are largely structured in those ways. Women will typically use five times as many words in a situation as men will. Also, while men will listen with just one side of their brains, women will use both sides, indicating more of a talent for multi-tasking. It is important to note that these are general, not absolute, tendencies in men and women. Within each gender there is a wide range of differences between individuals, thus creating a large gray area that one certainly could not describe as absolutely male or female. Thus one should not use these general tendencies as supporting a “biology is destiny” argument for locking men and women into certain rigid roles. By the same token, these are tendencies we cannot afford to ignore in discussing issues of gender differences.