Monogamy Evolved From Chest-Thumping To Caregiving
May 29, 2012

Monogamy Evolved From Chest-Thumping To Caregiving

John Neumann for

Chest-thumping and grunting alpha males, a study suggests, may be losing the battle for preferable females to males who can demonstrate caregiving and the ability to provide for a family, according to research published in the Proceedings of the National Academy of Sciences.

The research team says they have demonstrated mathematically that the transition to pair-bonding was based on female choice and faithfulness, so that providing for females became a better way of getting sex than showing competition between males, reports Adriana Barton for Globe and Mail.

The effect is most pronounced in low-ranked males who would have a poor chance of winning a mate in a fight. “Once females begin to show preference for being provisioned, the low-ranked males´ investment in female provisioning over male-to-male competition pays-off,” says Sergey Gavrilets of the National Institute for Mathematical and Biological Synthesis and a professor at the University of Tennessee-Knoxville.

The social contract works both ways, males would only provide for a mate who remained faithful, Dr. Gavrilets tells Kate Taylor of TG Daily. “That creates a co-evolutionary process where both provisioning and faithfulness increase in parallel.” According to his model, the quid pro quo predates human language and culture.

“This model deals with what animal biologists call social instincts and shows that some of these behaviors can be coded in our genes,” Dr. Gavrilets said. “Culture came much later and only augmented things that were already in place.”

Some scientists believe that ancestors of humans had chimp-like patterns of mating and child-rearing, reports Rosie Mestel of the Los Angeles Times. The transition to pair-bonding was a key step for our big-brained species, because our children take years and much energy to raise to independence. It´s hard for a mother to go it alone.

Gavrilets attempts to answer how that transition took place, saying that males that help feed and protect a smaller number of offspring can also be very successful, reproductively speaking – but only if they can be sure who their children really are or if they provide for all the young in a group. Otherwise, the “providers” are wasting resources on offspring that are not their own.

Owen Lovejoy, a biological anthropologist at Kent State University in Ohio, said the paper fits with his own thoughts on the evolution of monogamy.

Lovejoy, who edited Gavrilets´ paper, said he had theorized for decades that monogamy could be traced to males providing food to females. In a 2009 research paper, he proposed that monogamy was already in place in a 4.4-million-year-old member of the human family.

But David Buss, an evolutionary psychologist at the University of Texas at Austin and author of “The Evolution of Desire: Strategies of Human Mating,” said that although the paper offered a “plausible” explanation for what may have jump-started monogamy, it hugely simplified human sexual behavior.

The study reveals that female choice played a crucial role in human evolution and that future studies should include between-individual variation to help explain social dilemmas and behaviors, according to Gavrilets.