"Someone living on the Arctic Circle would have an eyeball that is 20 percent larger than someone living on the equator," Discovery News quoted co-author Robin Dunbar as saying.
"People living at high latitudes have greater visual acuity than those who live at the equator.
"The whole point is that they need to have better vision to compensate for the lower light levels at high latitudes, as indicated by the evidence we provide that visual acuity under ambient/natural light conditions remains constant with latitude," Dunbar, who is head of the Institute of Cognitive and Evolutionary Anthropology at the University of Oxford, said.
For the study, Dunbar and colleague Eiluned Pearce measured the skulls of 55 individuals from 12 different populations, focusing on the dimensions for orbital volume and cranial capacity. The people lived about 200 years ago.
But the scientists point out that brain size isn't necessarily correlated with intelligence.
"The point we're trying to make is that the larger brains of high latitude humans doesn't mean they're smarter, it just means they have increased the size of brain areas dedicated to vision, and this has increased brain size overall," Pearce explained.
The findings could help to explain why Neanderthals and their ancestors may have had larger brains than us.
The study published in the latest issue of the journal Royal Society Biology Letters.