July 27, 2011

Humans Evolved Larger Brains Nearer The Planet’s Poles

Researchers from Oxford University studying the eye sockets and brain capacity of 55 human skulls from 12 different populations across the world found people from northern parts of the world evolved bigger brains and larger eyes, aiding in coping with long, dark winters and dim skies, Reuters is reporting.

"Having bigger brains doesn't mean that higher latitude humans are smarter, it just means they need bigger brains to be able to see well where they live," explained Eiluned Pearce from Oxford's School of Anthropology, who led the study. "Their brains also need to be bigger to deal with the extra visual input."

"As you move away from the equator, there's less and less light available, so humans have had to evolve bigger and bigger eyes." 

The team, from the Institute of Cognitive and Evolutionary Anthropology, used skulls dating from the 1800s kept at museums in Oxford and Cambridge and were from indigenous populations ranging from Scandinavia to Australia, Micronesia and North America.

The same evolutionary trends that give relatively large eyes to birds that sing first during the dawn chorus, or species such as owls that forage at night, are also found to be active in humans.

Co-author Prof. Robin Durbar explains, "Humans have only lived at high latitudes in Europe and Asia for a few tens of thousands of years, yet they seem to have adapted their visual systems surprisingly rapidly to the cloudy skies, dull weather and long winters we experience at these latitudes."

The team took into account the overall body size of each individual by measuring the foramen magnum - the hole in the base of the skull that attaches to the spinal column.

These finding suggests that someone from Greenland and someone from Kenya will have the same ability to discern detail, but the person from the higher latitude needs more brainpower and bigger eyes to deal with the lower light levels.

The results, published on Wednesday in the journal Biology Letters, showed that the biggest brains, averaging 1,484 milliliters, were from Scandinavia, while the smallest brains, around 1,200 milliliters, came from Micronesia, The Guardian reports.


Image Caption: Skulls from the 1800s used in the study. Credit: Oxford University


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