Prehistoric conflict hastened human brain’s capacity for collaboration, study says

How humans evolved high intelligence, required for complex collaborative activities, despite the various costs of having a big brain has long puzzled evolutionary biologists. While the human brain represents only about two percent of the body’s weight, it uses about 20 percent of the energy consumed. Other costs of having a large brain include a need for extended parental care due to a long growth period, difficulties giving birth to larger-headed babies, and some mental illnesses associated with brain complexity. So how did the human brain evolve to become so large and complex?

Another long-running question is how did humans evolve strong innate preferences for cooperative behavior, as cooperative behavior is vulnerable to exploitation by cheaters and “free-riders.” A free-rider doesn’t contribute or cooperate and thereby undermines the effectiveness of the group’s collaborative effort, something scientists call “the collective action problem.” Thus, collaborative behavior is expected to be rare, and indeed, in animals it is typically limited to close relatives. Humans, however, are a unique species where collaboration is widespread and not limited to relatives.

In the new study published in the Journal of Royal Society Interface, lead author Sergey Gavrilets, a professor of ecology and evolutionary biology and mathematics at the University of Tennessee, Knoxville, and NIMBioS associate director for scientific activities, developed a mathematical model that offers answers to both evolutionary puzzles.