Blue eyes mutation
Making brown eyes blue
Brown is the predominant eye colour of people around the world. But many people of European descent have blue eyes, as one of the authors (DC) does. Blue-eyed people have less of a brown pigment known as melanin in their irises. Interestingly, the blue colour is not caused by blue pigment but by light scattering from the diffuse layer of the brown melanin, similar to how sunlight scattering off air molecules makes the sky blue.
Believing that blue eyes were likely the result of a genetic mutation, and thinking that the OCA2 gene determines the amount of melanin in our eyes, for some years researchers searched that gene for the mutation. But they couldn’t find it there.1
Then some researchers noted that two disorders that can result in albinism or reduced eye pigmentation, namely the Prader–Willi and Angelman syndromes, were caused by partial deletion not just of the OCA2 gene, but also another gene known as HERC2. Researchers subsequently discovered that the ‘blue eyes’ mutation is actually in the HERC2 gene, a gene that regulates the activity of OCA2.2 The mutated HERC2 gene strongly inhibits the OCA2 gene’s role in eye pigment production, drastically reducing the amount of melanin produced in the iris, resulting in blue eyes.
“Originally, we all had brown eyes,” explained lead researcher Professor Hans Eiberg of the University of Copenhagen, likening the HERC2 mutated gene’s effect on the OCA2 gene to that of “a ‘switch’, which literally ‘turned off’ the ability to produce brown eyes.”3 Given how little variation there is in blue eyes, the researchers conclude that all blue-eyed people have this same mutation, and share the same blue-eyed ancestor. According to Eiberg and his co-workers, that first blue-eyed individual likely lived in the Black Sea area about 6,000 to 10,000 years ago, during the “great agriculture migration” from Africa into northern Europe.2
However, that presumed date and ancestral source is based on evolutionary assumptions, whereas the Bible’s post-Flood, post-Babel chronology would put the timing of the blue-eyed mutation as occurring sometime in the past 4,000 or so years. Why would we say this? Well, if the mutation is only found in one subpopulation (Europeans), it would have to arise after Europeans separated from the rest of the world population.
Prior to Babel, we would expect the descendants of Shem, Ham, and Japheth to intermix (because there were no other people to marry!), so any genetic variant found among the pre-Babel peoples would be expected to be mixed up among the post-Babel peoples. There is a chance that the ‘blue eyes’ gene existed earlier but remained hidden because the ‘brown eyes’ gene is dominant over the ‘blue eyes’ gene. In the same way, ‘light skin’ genes are found all over Africa but are hidden by the dominant ‘dark skin’ genes.4 However, after millions of people across the world have had their DNA tested, it is clear that the genetic variants associated with blue eyes are highly correlated with people of European descent.
Note also that evolutionary theory looks to mutations as being evolution’s ‘engine’,5 i.e. the source of new genetic information by which evolution could have powered pond protozoa to become people over millions of years. However, there’s no evidence of any such information-gaining mutations here. Assuming brown eyes were the original colour, and there is good reason to think this, instead we see a loss of genetic information: the deletion of parts of genes, the switching off of the ability to produce brown eyes, the damaging of a gene’s ability to correctly regulate other genes, the inhibition of a gene’s production function.
All these are symptomatic of a world “in bondage to decay”, just as the Bible says (Romans 8:19–22). To borrow the colloquial words of a once-popular song, but with this cursed and fallen world sadly in mind: “Don’t it make my brown eyes blue”.
Are blue eyes harmful?
Although mutations can so damage genes that they affect survival, thankfully others are largely ‘neutral’ in terms of survivability, as the blue eyes mutation appears to be. Less melanin means more light will get through the iris. Individuals with blue eyes often report increased sensitivity to light, thus they might have some disadvantage in areas with strong sunlight (although nowadays they have the option of sunglasses, thankfully), which could be one reason blue eyes are more common in poorly sunlit areas. It is uncertain whether another factor in that could be the better vision in low light that has been claimed to be associated with blue eyes. Or, it might have nothing to do with selection for light sensitivity; in which case, the greater percentage of blue-eyed people in Northern Europe might just be due to chance. So those of us with blue eyes can soldier on yet.
References and notes
- Williams, Z., and Orwig, J., All blue-eyed people have a single ancestor in common, businessinsider.com.au, 22 September 2017. Return to text.
- Eiberg, H., and 6 others, Blue eye color in humans may be caused by a perfectly associated founder mutation in a regulatory element located within the HERC2 gene inhibiting OCA2 expression, Human Genetics 123(2):177–187, 2008 | doi:10.1007/s00439-007-0460-x. Return to text.
- University of Copenhagen, Blue-eyed humans have a single, common ancestor, sciencedaily.com, 31 January 2008. Return to text.
- Carter, R.W., Skin colour surprises, creation.com/skin-colour-surprises, 23 November 2017. Return to text.
- Williams, A., Evolution’s engine becomes evolution’s end!, Journal of Creation 22(2):60–66, 2008. Return to text.