Eye Color
“The eye is the jewel of the body.”
–Henry David Thoreau (American Essayist and Philosopher, 1817-1862)
In November we had a look at new data suggesting that eye color may have developed as a kind of “instant paternity test.”
Now scientists in Brisbane, Australia are reporting that they have uncovered the genetics of eye color, and that they are surprisingly simple. Which is just what we would expect if something were biologically important.
The research is published in the current issue of the American Journal of Human Genetics.
After studying 3,839 individuals, it turns out that of the six billion or so “letters” that make up the human genetic code, a handful of “single nucleotide polymorphisms” (SNPs – pronounced “snips”) are largely responsible for the color of your eyes. These SNPs consist of a change in just one “letter” in the genetic sequence. All the SNPs are located near a gene called OCA2. This gene produces a protein that helps give hair, skin and eyes their color. And mutations in OCA2 cause the most common type of albinism. So these gene mutations modify the amount of pigment in the iris: people with brown eyes have more pigment than people with blue. The odd one out is people with green eyes. In them the changes in the genes seems to have produced a functional change in the pigmentation protein itself.
This is interesting for another reason. There are a small number of medicines and clinical conditions that are associated with changes in the color of the iris. But I have also seen some people whose eye color has changed very rapidly in response to changes in mood, attention or concentration. I have also sometimes seen it happen when people have achieved some altered state of consciousness through prayer or meditation. Yet there is hardly any scientific research into this odd but uncommon phenomenon.
I did find two studies from Korea that attempted to associate a gene for angiotensin converting enzyme and the apolipoprotein e gene with iris type. The trouble with these studies was that they were very small and started with the assumption that iridology could be used to diagnose a physical problem, even though the research (1. 2. 3. 4.) has shown that it cannot.
I had assumed that these rapid changes in eye color had something to do with changes in blood flow in the eye, and that does remain the most likely explanation. But the question now is whether the SNPs associated with eye color are themselves modulated by mood, cognition or spiritual insight.
If you have ever observed changes in iris color in yourself or other people, I would be very interested to hear from you.
“All our souls are written in our eyes.”
–Edmund Rostand (French Poet, 1868-1918)
Dr. Richard G. Petty, MD is a world-renowned authority on the brain, and his revolutionary work on human energy systems has been acclaimed around the globe.
He is also an accredited specialist in internal and metabolic medicine, endocrinology, psychiatry, acupuncture and homeopathy. He has been an innovator and leader of the human potential movement for over thirty years and is also an active researcher, teacher, writer, professional speaker and broadcaster. He is the author of five books, including the groundbreaking and best selling CD series Healing, Meaning and Purpose. He has taught in over 45 countries and 48 states in the last ten years, but spends as much time as possible on his horse farm in Georgia.
I have several friends who have “hazel” eyes, and I have noticed that their eye color changes a lot. Sometimes they look light brown, sometimes they look green and sometimes they look gray. I had thought these changes had to do with the lighting, but maybe there is something else involved.
I know one family in which the mother, father and their 7 children all have hazel eyes, which change color a lot. However, I also know one girl who has hazel eyes, and neither of her parents have hazel eyes. Her mother has brown eyes, but her father’s eyes are gray. But the girl did tell me her father’s eyes sometimes look green or blue, too.
I have been told on more than one occasion that if I am either very happy or excited about something or get upset or angry that my eye colour changes from hazel to yellow. At least for people who know me it gives them a warning if I’m cross about something.
Thank you Jackie and Louisa for those VERY interesting comments.
It is fascinating that both of you have noticed these changes in hazel colored eyes. That seems to be the most common obersation, though I’ve also observed it myself in some people with blue eyes and and a few Asians with deep brown eyes.
The switch from hazel to yellow as a barometer of mood is exceptionally interesting. It is amazing that there is so little research on something so important.
Kind regards,
RP