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March 02, 2006
The Naked Ape and the Other Partially Naked Primates
At the beginning of chapter 27 of Following the Equator, Mark Twain attributed this to "Pudd'nhead Wilson's New Calendar:"
Man is the Only Animal that Blushes. Or needs to.
And those words are a powerful metaphor for much of the sins of Homo sapiens but it isn't literally true. Many primates show fear, sexual readiness and other "emotions" through the reddening or whitening of their skin due to the amount of oxygenated hemoglobin is in the blood near the surface.
Mark Changizi, a theoretical neurobiologist at Cal Tech is reporting on the work of a team of scientists that suggests that color vision in primates may have evolved for the purpose of detecting these subtle changes in skin color in both the face and the rump of other primates of their own species.
The prevailing theory is that color vision in primates developed to aid in gathering nutritious food.
"But if you look at the variety of diets of all the primates having trichromat (three-color) vision, the evidence is not overwhelming."Instead, Changizi and colleagues report in the current issue of the journal Biology Letters, the system seems adapted especially to find the colors prevalent in primate skins -- notably changes due to how much oxygenated hemoglobin is in the blood.
[snip]
And the three-cone system can help a primate tell not only if a potential partner is having a rush of emotion in anticipation of mating, but also if an enemy's blood has drained out of his face due to fear.
"Also, ecologically, when you're more oxygenated, you're in better shape," Changizi said. That may be why humans value rosy cheeks, he said.
The clincher -- Changizi said old-world primates that have the three-cone vision are also all bare-faced and bare-butted."There's no sense in being able to see the slight color variations in skin if you can't see the skin," Changizi said.
"This could connect up with why we're the 'naked ape,'" he added. [Reuters]
I would like to see the data but the idea is intriguing. Like vision itself, color vision is an example of convergent evolution. If Changizi and his team are correct, the evolutionary advantage of color vision in primates may have been literally quite different from the evolutionary advantage of color vision for the birds and the bees. Or perhaps better, the evolutionary advantage of color vision in primates may have come from the more figurative meaning of "the birds and the bees."
Posted by DuaneSmith at March 2, 2006 07:23 PM | Read more on Evolution |
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