Few phenomena are more remarkable or complex than
the sensation of color. It pervades every moment of our lives, from the
red-orange of sunrise to the depths of our dreams. Even our emotions reflect
the sensation of color. We "feel
grow "green with envy" and "red with anger." A recent
discovery sheds important light on one aspect of human color vision – that
of seeing red.
The scientists focused on a gene that allows humans
to see red, a gene found only on the X chromosome. Variations in this gene can
allow expanded color vision. Since men have only one X chromosome compared to
the two women possess, they get one less crack at this expanded vision.
Brian Verrelli of Arizona State University and Sarah Tishkoff of the University of Maryland analyzed genetic data from 236 people from around the world. Specifically, they studied a gene on the X chromosome known as OPN1LW, which codes for a protein that detects visible light in the red spectrum. Exchange of material between this gene and a neighboring gene associated with green light leads to a high amount of genetic variation but can result in color blindness if the process goes awry. Among the study participants the researchers found 85 variants of the gene. "That's approximately three times higher than what you see at any other random gene in the human genome," Tishkoff says. "Usually it's a bad thing to have too much change in a gene, and natural selection gets rid of it. But in this case we're seeing the reverse."
Such variations have been preserved throughout evolution and are thought to be beneficial. The two scientists speculate that it might have begun in the prehistoric era, where acute color vision was of use in separating poisonous crimson berries from their edible burgundy cousins. Since women did much of the gathering (while men did the hunting), women developed better red sensitivity.
About the authors
First published in May 2005, while John and I were at the AGTA GTC. Working with John was one of the greatest pleasures of my life, sadly far too brief. Looking back, I can only wonder what might have been… Thanks to Donald Allen for suggesting the above article.
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Posted 14 October, 2011; last updated 7 March, 2013