Variation among primate eye color may be the result of ambient light in their habitats, new research finds.
This helps tip the balance towards an ecological, rather than sexual selection explanation, for the evolution of blue eye color in humans.” Understanding that ambient light, instead, may have an impact in the appearance of primate eyes brings a fresh perspective to this field,” says Perea-García. The researchers found that species living farther from the equator tend to have lighter conjunctiva (the tissue surrounding the iris), not unlike skin pigmentation in humans. This was also the preferred explanation for diversity in skin pigmentation, until evidence tipped the balance towards protection from UV rays. Blue light helps us tune our circadian clock to adjust energy levels by stimulating special receptors in our retina. This idea, however, has received little support from experimental studies in species other than humans.