London: People living in the north have bigger brains than those staying in the south, says a study.
Unfortunately, that doesn`t necessarily mean northerners are more intelligent than people from the south --just that they have evolved to cope with the longer winters and greyer skies in northern climes, say British researchers.
In fact, a team at Oxford University, who measured the brain volume of 55 skulls from around the world, came out with this intriguing theory that people from countries further from the equator have more grey matter and larger eyes than those from sunnier parts, `The Daily Telegraph` reported.
This is because living in low light conditions means the eyes and brain need to work harder in order to process images to a good level of detail, or "high resolution", say the researchers.
Lead author Eiluned Pearce said the study suggests that the bigger brains and eyes are needed to see properly in dimmer light.
"As you move away from equator, there`s 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," she was quoted as saying.
The researchers said the findings could theoretically even apply to different communities in a particular country.
In fact, their analysis of 55 skulls from 12 nations, dating from the 1800s, showed people in northern areas have evolved to grow larger eyes and visual areas of the brain.
Having wider pupils allows the eyes to take in more light, while a bigger retina is able to distinguish more detail, producing a higher-resolution image, according to the researchers.
They examined the volume of eye sockets and brain cavities in the skulls and found a direct link to the latitude of their country of origin.
While English people had an average brain size of 1,416ml, the figure in Micronesia, which lies very near the equator, was just 1,200ml. In contrast Scandinavians, the most northerly population tested, had a brain capacity of 1,484ml -more than 20 per cent higher than Micronesia.
A similar difference was seen in eye volume, with English skulls indicating an average of 26.22ml, compared with 26.83 in Scandinavia and 21.83 in Micronesia.
Co-author Prof Robin Dunbar added: "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 study has been published in the `Biology Letters` journal.