Ever wondered why some people have intense blue eyes, especially people with origins in Europe. There has been plenty of speculation, well a recent study from Liverpool John Moores University may provide an answer.
The work, titled “Effect of iris pigmentation of blue and brown eyed individuals with European ancestry on ability to see in low light conditions after a short-term dark adaption period” by Faith Erin Cain and Kyoko Yamaguchi, investigates the impact of iris depigmentation on visual acuity in low light conditions. It suggests that individuals with blue eyes, due to their iris depigmentation, may have an adaptive advantage in seeing better in low light after a brief adaptation period. This finding indicates that the evolution of blue eyes in Europe could be linked to an adaptive advantage in certain lighting conditions.
“In this study 40 participants took part in a simple eye test in increasing luminance to examine if there was a difference in capacity to see in low light conditions between blue and brown-eyed individuals after a brief adaptation period. Blue eyed individuals were identified to have significantly better ability to see in lower lighting after a short adaption period than brown eyed individuals making it likely depigmented irises provide an adaptive advantage (p=0.046). Superior ability to see in low light conditions could be the result of increased straylight in depigmented irises, which in light luminance is disadvantageous but in low light conditions may provide an advantage.”
So this explains the blue colour, but just why people in Europe during ancient times would develop such an ability is open to suggestion, one theory being that gathering food in the periods of dawn and dusk when daylight is less intense would be preferential to avoid the heat of the day or to avoid predators.
Brown eyes, have been and still are the most dominant phenotype for humans around the world, while indications are that blue eyes, in contrast, became the dominant colour for Europeans (almost exclusively in Western Europe). This study then, although not comprehensive, does shed a little light (pun intended) on the purpose of blue eyes.
You can read the entire study online, by clicking HERE.
