But humans are clueless when it comes to pheromone signals, according to University of Michigan evolutionary biologist Jianzhi "George" Zhang. He believes color vision put our pheromones out of business.
Our closest relatives on the primate family tree rely on "sexual swelling" and gaudy, colorful patches of skin to signal their reproductive fitness and fertility, Zhang said. In fact, though humans and these apes still carry genes that should create pheromone receptors in our noses, these genes have mutated to the point that they are merely pseudogenes---they don't function any more.
Zhang has used the genes of people and primates to get at the answer to this intriguing puzzle. Zhang (pronounced Zong), is an assistant professor in Ecology and Evolutionary Biology in the College of Literature, Science and Arts. Zhang's paper on the topic appears this week in the online Proceedings of the National Academy of Sciences.
Zhang believes that a significant gene duplication made the difference and that it happened sometime between 23 million years ago and the split of the New World and Old World primates about 35 million years ago.
An ancestor of the Old World primates (humans, chimps, gorillas, orangutans, gibbons, baboons and guerezas) developed a second copy of the red/green color-vision gene, which resides on the X chromosome. Female New World monkeys have full color vision because females have two X chromosomes that harbor both red and green color vision genes. But males only have one X chromosome, so New World males have only one copy of either the red or green gene, and that leaves them color-blind. A
Contact: Karl Leif Bates
University of Michigan