Forget the sexual revolution of the 1960s. It seems the move to monogamy, maybe several million years ago, might have been the biggest revolution in romantic relationships.
According to a new study published in the journal Proceedings of the National Academy of Sciences, non-dominant males, who couldn't compete directly with their alpha or beta counterparts, would woo females by providing for them and their children. The females began preferring the breadwinning male to the bigger or stronger ones, and would become faithful to him.
"Once females begin to show preference for being provisioned, the low-ranked males' investment in female provisioning over male-to-male competition pays-off," explains study author and University of Tennessee in Knoxville professor of ecology, evolutionary biology and mathematics, Sergey Gavrilets.
A real insurgency by the lower echelon of males.
Through a mathematical model, Gavrilets gives his best explanation for what became modern monogamy. A scenario where low-ranking omega males skipped macho competitions and turned to nurturing females instead.
"Gavrilets has a good reputation, particularly in providing mathematical foundations for things that many anthropologists and psychologists construct stories about," says evolutionary psychologist and University of Victoria teaching professor, Martin Smith.
Smith mentions some other surprising reasons that could explain why humans opt for committed relationships. One of them has been the evolution of humans walking on all fours to walking on only two legs. He implies this evolution made men more nurturing.
"As soon as we could stand upright, we could bring food to other people," he explains.
Who knew that having free hands would make us more faithful.
But former University of California anthropology professor, Sarah Hrdy thinks Gavrilets' theory might be overlooking some important factors. She tells TIME that cooperative child-rearing among women was an important factor in the evolution of families. The father was not the only one helping with parenting.
"I don't think human mothers in the past could count on the long-term survival and fidelity of provisioning mates any more than mothers today can," she says. "Males are responding to a wider range of factors than can be represented in such a model."
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And in case you are not convinced that alpha-males should be shunned in favour of non-dominant males. Toronto-based psychologist Tami Kulbatski will tell you otherwise. She sees women who've opted for the modern alpha-male coming into her practice with depression or anxiety.
"The qualities which initially drew them to their partners are the same ones that are now causing bitter fights, diminished feelings of self-worth and emotional turmoil," she says.
"Women seeking a long-term, monogamous, and mutually-fulfilling relationship," she advises, "should forego the tyrant in favour of the team-player."