Population Density Triggered Rapid Growth of Human Brain Over Past 2 Million Years

For the past 2 million years, the size of the human brain has tripled, growing much faster than other mammals. Examining the reasons for human brain expansion, University of Missouri researchers studied three common hypotheses for brain growth: climate change, ecological demands and social competition. The team found that social competition is the major cause of increased cranial capacity.

To test the three hypotheses, MU researchers collected data from 153 hominid (humans and our ancestors) skulls from the past 2 million years. Examining the locations and global climate changes at the time the fossil was dated, the number of parasites in the region and estimated population density in the areas where the skulls were found, the researchers discovered that population density had the biggest effect on skull size and thus cranial capacity.

"Our findings suggest brain size increases the most in areas with larger populations and this almost certainly increased the intensity of social competition," said David Geary, Curator's Professor and Thomas Jefferson Professor of Psychosocial Sciences in the MU College of Arts and Science. "When humans had to compete for necessities and social status, which allowed better access to these necessities, bigger brains provided an advantage."

The researchers also found some credibility to the climate-change hypothesis, which assumes that global climate change and migrations away from the equator resulted in humans becoming better at coping with climate change. But the importance of coping with climate was much smaller than the importance of coping with other people.

"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," said Drew Bailey, MU graduate student and co-author of the study. "Our research tells us that competition, whether healthy or not, sets the stage for brain evolution."

Posted by Jason McManus.

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Comments

[Robert]

The important thing about climate change, is cyclic climate change versus a single event. Geologic evidence indicates that starting two millions years ago the earth started undergoing regular ice ages events, lasting around 20,000 years with 10,000 year warm periods in between. Intelligence provides the quickest means to achieve adaptability between these significant relativity short term events based upon an effective mammalian evolution time scale. The time scales are too short for mammals to evolve to suit new environmental conditions giving the advantage to a species that doesn't need to evolve to thrive in conditions that differ from it's evolutionary basis, man, wear clothes, start fires and build shelters. Of course people eventually have to compete with other groups of people for access to resources, the biggest, most versatile group with capacity for specialisation (warriors) wins and as such continues to evolves whilst the other group becomes extinct or is in part absorbed. So humanity is a combination of individual evolution as well as social evolution and how both evolutionary tendencies interact.

[Good Grief]

Pop-science writers traffic in some of the most obvious ideological seductions. It's obvious and commonsense that early human existence was nasty, short, solitary, brutish, and competitive. That anthropology would suggest otherwise means nothing.

[Daniel Vareika]

To whom it may concern,

Where did you get the image?
I am most impressed by it and would love to get a high def of it.

Thanking you in advanced,

Daniel Vareika

[multicast live]

The time scales are too short for mammals to evolve to suit new environmental conditions giving the advantage to a species that doesn't need to evolve to thrive in conditions that differ from it's evolutionary basis, man, wear clothes, start fires and build shelters.