Tuesday, 23 Jun, 2009 Science

Competition Increased the Size of Human Brain?


Over the past 2 million years human brain continuously increased in size, in fact over this period it tripled, showing a much faster evolution compared to other mammals.

Researchers at the University of Missouri decided to analyze the reasons for human brain evolution. They examined three common hypotheses that explain human brain expansion: climate change, ecological demands and social competition. The latter was found to play the main role in the evolution of human brain.

In order to test all the hypotheses, scientists gathered information from 153 skulls belonging to humans and our predecessors for the past 2 million years. They studied the alterations in the global climate during the time when the skull remnants were dated and the number of parasites found in the region and carried out calculations on the population density in the areas where skulls were discovered. Researchers found that population density played the main role in the development of the skull and thus in the evolution of cranial capacity.

"When humans had to compete for necessities and social status, which allowed better access to these necessities, bigger brains provided an advantage," said David Geary, Thomas Jefferson Professor of Psychosocial Sciences in the MU College of Arts and Science.

In addition, scientists found evidence of the climate-change hypothesis, which states that the change in the global climate along with migrations from the equator made humans more flexible in adapting to new climate conditions. However, coping with other humans was much more important than adapting to new climate, reports News Bureau at the University of Missouri.

Drew Bailey, MU graduate student who co-authored the research explained: "Brains are metabolically expensive, meaning they take lots of time and energy to develop and maintain." This is why it is crucial to understand why human brains continued to develop faster than other animals, Mr. Bailey added.

"Our research tells us that competition, whether healthy or not, sets the stage for brain evolution," he said. The study called "Hominid Brain Evolution" and its results were published in the journal Human Nature.

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