The Ancient Sexual Revolution That May Have Spurred Human Monogamy
Monogamous, romantic love — or, more prosaically, pair-bonding — may have evolved in a sexual revolution that could have laid down the roots of the modern family, according to an intriguing new mathematical model.
Researchers have long wondered why — unlike our sexually promiscuous chimpanzee-like ancestors — humans developed strong pair bonds with individual partners. It’s thought that at one time, human ancestors did engage in chimp-like habits of sex and child-rearing, in which strong alpha males mated freely with the females of their choice, and then left the child-raising duties to them. So, the question is, How did we got from there to the modern-day monogamous, two-parent family?
“People have been discussing ways by which the transition from promiscuity to pair-bonding could have occurred and there are various different scenarios,” says study author Sergey Gavrilets, distinguished professor of ecology, evolutionary biology and mathematics at the University of Tennessee in Knoxville. “What I’ve done is shown mathematically that some of these scenarios are more likely than others.”
Gavrilets study suggests that a sexual revolution occurred, led by low-ranked males and faithful females. Low-ranked males, who had no hope of physically overcoming the dominant members of their groups, instead began providing extra food to certain females, to curry sexual favor. These females responded by remaining faithful to their breadwinning males. That change in behavior favored the reproductive success of these monogamous couples — pair-bonding offered a greater likelihood that their children, who took a lot of effort to raise, would survive — ultimately moving humanity away from a promiscuous mating system dominated by alpha and beta males.