Monkeys' faces evolved to avoid crossbreeding 
 
 Researchers used human face recognition techniques to identify and compare guenons' features 
 
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 Guenon monkeys' colourful and varied faces have evolved as a way to avoid crossbreeding, scientists have found. A close study of more than 20 guenon monkey species reveals these sociable animals may rely on their distinctive patterns to prevent interbreeding. Guenons - Cercopithecini - are a group of more than 25 species of monkeys which originated in the forests of Central and West Africa. Many different species of guenons live side-by-side meaning mating with other species, which could lead to infertile offspring, is a possibility. The findings are reported in the journal Nature Communications and researchers say they are the best evidence to date of visual signs acting as a barrier to breeding across species. Researchers studying primates in South America have discovered a similar pattern, with more-complex facial features among primates who need to quickly recognize members of their own species.
– 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.