Researchers from Oxford University have discovered that humans who live in polar regions (far from the equator) have evolved bigger eyes and larger brains to help them process information at the low level of light typical in those areas. A team of anthropologists led by Eiluned Pearce collected 55 skulls dating from the 1800s that represent 12 different populations around the world. By measuring the eye socket and brain volumes and plotting the data against the latitude of each individual’s home country, the researchers were able to compare eye and brain size with location.
The researchers found a positive correlation between size and latitude. People from cold climates, like the northern-European country of Scandinavia, had the biggest brains, and people from warm climates close to the equator, like Micronesia, had the smallest. According to the researchers, these bigger brains are not the result of increased intelligence, but rather the need for a larger portion of the brain devoted to vision. This helps the brain overcome the low-light conditions caused by bad weather and long winters in northern climates.
Professor Robin Dunbar, Director of the Institute of Cognitive and Evolutionary Anthropology at Oxford University, said in a press release:
“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 research, which was published in the journal Biology Letters, builds on previous observations about the correlation between eye size and light level in other animals. Birds with large eyes are known to be the first to start singing when the sun rises, and primates with the biggest eyes are known to be able to eat and forage at night.