m-file Men and Women Literally See the World Differently SO YOU’RE HAVING that discussion about what color to paint the
living room. She says, “How about something in an Iced Mauve?” He says,”You mean there are colors besides beige?” It could be you’ve encountered an ancient gender color divide that can be chalked up to evolution. A new University of Maryland study shows that the same kind of gene variety that causes color blindness—usually in men—also may give humans—especially women—a better perception of color. Sarah Tishkoff, assistant professor of biology, and former Maryland postdoctoral fellow Brian Verrelli, now an assistant professor at Arizona State University, studied DNA from more than 200 subjects from different geographical populations around the world, and, to their surprise, found that one of the genes connected to color vision has maintained an unusual amount of genetic variation, possibly for millions of years of human evolutionary history. “Usually, it’s a bad thing to have too much change in a gene, and natural selection gets rid of it,” says Tishkoff, “but in this case, we’re seeing the reverse. Natural selection is acting to maintain that variation.” The Maryland researchers found that variation in this color perception gene may have given women in particular the ability to see more subtle shades of colors.Women have two X-chromo-
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somes, men only one. Because this color vision gene resides on the X-chromosome, rare detrimental changes at this gene cause colorblindness in males—eight percent of the world’s men are color blind—whereas females are likely to have at least one good copy of the gene. Tishkoff and Verrelli speculate that in a time when humans were hunter-gatherers, enhanced color perception would have allowed women, who were traditionally gatherers, to better discriminate among colored fruits, insects and background foliage. “Men and women literally may be seeing the world differently,”Tishkoff says. The findings also suggest, says Tishkoff, that geneticists may want to look at the impact subtle changes have in natural selection, especially in disease prevention. “It’s long been thought that if it’s not a dramatic change, it doesn’t matter. But we see in this study that subtle changes can make a difference.” Tishkoff uses DNA to search for the origins of modern man, and is especially interested in the role infectious disease has played in humans. In 2003, she was named one of the country’s top 10 “Brilliant Young Scientists” by Popular Science magazine. —ET
ILLUSTRATION BY MIRA AZARM