How many times have you heard people say that they have, or love, blue eyes? The problem is, that the perception of eyes being blue is an optical illusion.
Most babies when they are born will have what appear to be blue eyes. This is because babies have no eye pigment. However, if the child has inherited brown eyes from a parent, the iris of the eye will darken as the pigment (melanin) develops with age.
Melanin absorbs light. However, eyes that appear blue, have very little melanin in the turbid front layer and so, the light travels through the translucent iris and scatters. This is called Tyndall scattering. Blue wavelengths of the light spectrum are shorter than other wavelengths, so, they scatter more efficiently.
Blue eyes are the result of a genetic mutation. Research by the University of Copenhagen shows that a genetic mutation affecting the OCA2 gene took place in a single individual 6000-10, 000 years ago and this turned off the melanin pigment production. Professor Eibergfrom from the university said that all eye colours can be accounted for by the amount of melanin in the iris.
The inheritance pattern of blue eyes is in general, considered a polygenic trait, meaning that it is controlled by the interactions of several genes, not just one.
DNA studies conducted on ancient human remains have confirmed that light skin, hair and eyes were evident at least tens of thousands of years ago on Neanderthals, who lived in Eurasia.
Books To Read
Europe: A Natural History, by Tim Flannery, Europe - modern humans arrived in Europe 40000 years ago.
