Northerners evolved more developed visual processing to help them cope with long winters and grey skies, a study suggests.
Scientists measured the eye sockets and brain capacity of 55 human skulls representing 12 different populations from across the world.
They found that the further north of the equator people lived, the bigger their eyes and visual brain regions were.
Both are adaptations to low light that have only appeared since humans moved into northern Europe and Asia, a very short length of time in evolutionary terms.
Lead researcher Eiluned Pearce, from Oxford University’s School of Anthropology, said: “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. 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.”
Humans seem to have adapted relatively quickly to changes in latitude through an evolutionary response mechanism.
Co-author Prof Robin Dunbar, director of the Institute of Cognitive and Evolutionary Anthropology at Oxford University, said: “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 cloudy skies, dull weather and long winters we experience at these latitudes.”