There are currently three main schools of thought dealing with explaining why human brain capacities increased dramatically over the past 2 million years or so, say experts at the University of Missouri.
One of them says that climate change led to this adaptation, another argues that ecological demands were responsible, and the third holds that social competition was the main catalyst.
The MU team believes that it was social competition and an increase in population density that made our brains three times larger today than they were only 2 million years ago, Daily Galaxy reports.
According to the investigators, the new study covered all three hypotheses. At first, experts collected data about our species and its ancestors. More than 153 skulls spanning far back into the the past were analyzed, measured and compared during the work.
Each of the fossils was dated, and experts also took into account factors such as the global climate at the time when that hominid lived, and the area where they carried out their daily activities.
Other possible influences that were taken into account include population density, the number of parasites available at the time, and the incidence of serious diseases that plagued the world then.
The conclusions were fairly straightforward – population density had the biggest effect of the average size of the human skull, and therefore on our species' brain capacity.
“Our findings suggest brain size increases the most in areas with larger populations and this almost certainly increased the intensity of social competition,” explains investigator David Geary.
“When humans had to compete for necessities and social status, which allowed better access to these necessities, bigger brains provided an advantage,” adds the expert, who is Curator's professor and Thomas Jefferson professor of psychosocial sciences at the MU College of Arts and Science.
“Brains are metabolically expensive, meaning they take lots of time and energy to develop and maintain, making it so important to understand why our brains continued to evolve faster than other animals,” adds Drew Bailey.
“Our research tells us that competition, whether healthy or not, sets the stage for brain evolution,” he adds. Bailey is a MU graduate student and also a coauthor of the new study.