"Perhaps those with blue eyes may have been able to withstand the dark, depressing days of the Neolithic European winters better than those with brown eye colour?" Notably, he says, the eye has special neurones in the retina that can detect blue light and use this to help regulate circadian rhythms. He says blue eyes have been linked to people coping better with seasonal affective disorder, a major depressive illness that occurs when there are long periods of low light. This could have been an advantage to hunter gatherer women who needed to identify and collect plant foods - indeed blue eyes may even have evolved in women first.īut Sturm has another idea. There's also the idea that blue eyes were advantageous because they perceive stationary objects better than moving things. So scientists have come up with a range of other hypotheses to explain the evolution of blue eyes, including the idea that they were more sexually attractive than brown eyes - "The Paul Newman effect," quips Sturm. ^ to top The 'Paul Newman effect' and other ideas Such archaeological evidence contradicts the idea that the need for sunlight to make vitamin D drove the evolution of blue eyes, along with light-coloured skin.
#Percentage of blue eyes in america skin
"This individual had light blue eyes but dark skin and that was the great surprise because we always though these things were co-evolving and we expected light skin to evolve first," says Sturm. His genes told them that while this man had dark skin and dark hair, he also had blue eyes. In 2014, Sturm and colleagues reported on ancient DNA from a 7000-year-old tooth belonging to a hunter gatherer dubbed La Brana 1, unearthed from the north-west of Spain. More importantly, there is evidence that blue eyes evolved before light skin - at least 7000 years ago.
There is no evidence that light-coloured irises let in more light or help you see better in low light than dark coloured irises. This gradient gave rise to the 'vitamin D hypothesis', which is the idea that light coloured skin, hair and eyes co-evolved as humans moved into latitudes where shorter days and summers meant they got less sunlight.īut, there's a problem with this idea, says molecular geneticist Associate Professor Rick Sturm of the University of Queensland.
In Africa dark eyes, skin and hair are the norm, but blue eyes are more common in southern Europe and even more common in northern Europe, where 70 per cent of people have blue eyes. Blue eyes have been around for at least 7,000 years but we still don't know exactly why they evolved.īrad Pitt has them, Paul Newman had them - but when it comes to the human population as a whole, blue eyes are not that common.Įxperts are not sure when blue eyes first evolved, but there are some interesting theories out there as to why they evolved.
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