Hans Eiberg and the Genetics of Blue Eyes
Danish geneticist Hans Eiberg (b. 1945) has made important contributions to the mapping of the human genome, and has also contributed to the discovery of genetic markers for rare genetic diseases such as Batten disease, cystic fibrosis, and various diseases of the eye. He is best known, however, for his discovery of the genetic mutation that causes blue eyes. He has been conducting this research since 1996, when he first targeted the OCA2 gene as being responsible for eye color. Since then, he and his team from the University of Copenhagen Department of Cellular and Molecular Medicine have been examining mitochondrial DNA and comparing the color of blue-eyed people from populations in countries ranging from Denmark to Jordan and Turkey.
Where do Blue Eyes Come From?
According to research conducted by Eiberg, people with blue eyes evolved from a common ancestor. He and his colleagues were able to track down the genetic mutation (which took place roughly 6,000 to 10,000 years ago) that causes the eye color of all blue-eyed people who have been alive since. Prior to this genetic mutation, all human beings had brown eyes.
The genetic mutation itself affects the OCA2 gene, which results in the creation of a "switch" that affects its ability to produce brown-pigmented eyes. It is possible to think of this switch as a "dilution" of sorts, namely a "dilution" of brown pigment to blue. This "switch" does not turn off this ability completely, however. If the OCA2 gene is destroyed or "turned off," it eliminates all melanin in the individual’s skin, hair, and eyes, resulting in albinism. This blue-eyed mutation is not a "negative" mutation in the sense that it does not impact health, longevity, or ability to survive.
What About Eyes of Other Colors?
This, of course, leads to the question: what about people with green, hazel, or grey eyes? Blue-eyed individuals are the only ones who can be traced to a common ancestor. This means that people with eye colors that range from brown to hazel to green simply have variations in the amount of pigment present in the iris. In other words, these individuals, have a range of variations in the area of their DNA that controls melanin production.
This post is part of the series: Pioneers in Genetics
- Famous Scientists in Genetics: Hans Eiberg
- Pioneers in Genetics: D. Bernard Amos and the Genetics of Individuality
- Famous Scientists in Genetics: William Bateson