Guenon monkeys are renowned for their colorful, distinctive faces, which vary from species to species. The reason? It's all part of a strategy to help the monkeys identify their own species and avoid crossbreeding with others, new research finds. Guenon monkeys, sometimes known as cheek pouch monkeys, are a group of perhaps 30 species that tend to live side by side. To prevent mating across species and possible unhealthy offspring, researchers think each species developed varying features—like mohawks, pursed lips, or white noses—as markers, LiveScience reports.
US and UK researchers spent a year and a half snapping photos of 22 guenon species, then compared their features using a human-face-recognition program—the first time such a thing has been used on non-humans. What they found: The monkeys' faces evolved to look different from guenons in other species, especially those with whom they were in close contact, reports the BBC. "In other words, how you end up looking is a function of how those around you look," a researcher says. (Read more monkeys stories.)