Larger brains and eyes go with living in the high latitudes: study
"They need bigger brains to be able to see well where they live"
Coping with the Arctic winter’s long nights and short days may bring some hidden benefits to people living in the high latitudes.
That’s because the further away that human populations live from the equator, the bigger their brains and eyes become, suggests a new study in the journal Biology Letters.
By studying skulls from 12 different populations at varying latitudes, Oxford University scientists determined that people living in places with long winters evolved bigger eyes and brains to better process what they see.
The bigger vision areas in the brain help cope with the low light levels experienced at high latitudes, a July 27 university news release said.
But “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,” said Eiluned Pearce from Oxford’s Institute of Cognitive and Evolutionary Anthropology, lead author of the new study. “As you move away from the equator, there’s less and less light available, so humans have had to evolve bigger and bigger eyes. Their brains also need to be bigger to deal with the extra visual input.”
The larger eye socket volume is also likely linked to cold weather and the need to have more insulating fat around the eyeball.
The researchers measured the eye socket and brain volumes of 55 skulls, dating from the 1800s, from museum collections.
The skulls used in the study were from the indigenous populations of England, Australia, Canary Islands, China, France, India, Kenya, Micronesia, Scandinavia, Somalia, Uganda and the United States.
For their study, researchers plotted the volume of the eye sockets and brain cavities against the latitude of the central point of each individual’s country of origin.
They found that the size of both the brain and the eyes could be directly linked to the latitude of the place from which the individual came.
On average, the eyeballs of people who lived within the Arctic Circle were 20 per cent bigger than those who lived near the equator.
“High latitude humans may require larger eyes to attain the same level of acuity as those living at lower latitudes,” the study says.
From measuring the brain cavity, the research suggests that the biggest brains belonged to populations in Scandinavia with the smallest being Micronesians.
Previous research has looked at the links between eye size and light levels, finding that birds with relatively bigger eyes are the first to sing at dawn in low light.
The eyeball size across all primates, such as apes and lemurs, has been found to be associated with when they choose to eat and forage – with species with the largest eyes being those that are active at night.