MU researchers link brain growth to social competition
COLUMBIA — An MU study shows the reason the human brain has tripled in size in the last 2 million years could be due to social competition.
MU researchers David Geary, a psychosocial sciences professor, and Drew Bailey, a graduate student, studied 153 hominid skulls and established population density as a leading factor.
The focal and primary type of skull in the research originated in Ethiopia and expanded based on population chronologically and demographically, outward to Asia, Europe and southern Africa, Geary said.
They found that a larger population led to more social competition, a process which Geary compared to a social ladder.
"People are jockeying, manipulating and competing their way up that ladder," Geary said, also comparing this phenomenon with the TV show "Survivor."
Geary claims "higher" access species secured more resources, such as food, mates and shelter, whereas "lower" access species tend not to be as fortunate.
"The lower you are on the ladder, the higher your risks are," Geary said.
The more a population would decrease as the lower species faded out, the more the "average" species would be forced to compete to keep up and thus, the cycle would start over again, Geary said.
With this growth, specific parts of the brain that deal with social problems, such as the neocortex, have grown in size, Bailey said.
Bailey said that in recent evolutionary history, humans have focused on competing against one another more than other factors, such as animals.
"Humans are really concerned with other humans," Bailey said. "It's what we do."
This data found in human brain growth can be used to study other species and society today, Geary said.
Geary said the brain has been increasing for 4 million years, but found the most major size increase to have happened in the last 100,000 years.
Social competition beat out two other hypotheses of climate change and ecological demands because it was found to be most consistent, Bailey said.
Climate change has been calculated using latitude and longitude location in comparison with the low, high and mean temperatures over time, along with sea floor sediments as a proxy to figure out how climatic stimuli affected brain size. But the social competition research provided five times the data of climate change, Geary said.
"I hope this study encourages other studies," Bailey said.