Dark winters led to bigger brains
Reported July 29, 2011
UK scientists have identified a link between bigger eyes and brains and living at high latitude.
The team from Oxford University found that the features had developed to help people cope with poor light during long winters and cloudy days, though the bigger brains did not make them more intelligent.
Writing in the Royal Societys Biology Letters journal, they revealed how the findings emerged after measuring the eye sockets and brain volumes of 55 skulls from 12 populations across the world, and then plotting the results against latitude.
Lead author Eiluned Pearce said: We found a positive relationship between absolute latitude and both eye socket size and cranial capacity.
Both the amount of light hitting the Earths surface and winter day-lengths get shorter as you go further north or south from the equator.
We found that as light levels decrease, humans are getting bigger eye sockets, which suggests that their eyeballs are getting bigger.
The team, from the Institute of Cognitive and Evolutionary Anthropology, used skulls dating from the 1800s – kept at museums in Oxford and Cambridge and from indigenous populations ranging from Scandinavia to Australia, Micronesia and North America.
The largest brain cavities came from Scandinavia, while the smallest were from Micronesia.
Co-author Prof Robin Dunbar said that while humans had only lived at high latitudes in Europe and Asia for a few tens of thousands of years, they appeared to have adapted their visual systems surprisingly rapidly to the cloudy skies, dull weather and long winters at such latitudes.