A new study using facial recognition software on monkeys shows primates developed distinctive markings to help them avoid interbreeding.
Different species of guenon monkeys have varied facial features, such as different colored eyebrow patches, ear tufts, nose spots, and mouth patches.
Using 1,400 photographs of the faces of nearly two dozen guenon monkey species and a facial recognition algorithm called the eigenface technique, scientists from New York University and the University of Exeter found the different markings allow the animals to recognize members of their own species. This helps avoid interbreeding, which could lead to infertile offspring, an evolutionary dead-end.
Indigenous to Central and West African forests, many different species of guenons live, feed, and sleep together, and could easily interbreed. In the 1980s, an Oxford zoologist theorized that the facial changes had evolved to prevent that. The new analysis supports that hypothesis - showing that face patterns of guenon species whose territories overlap are more visually distinctive than those who are more geographically distant.
Writing in the journal Nature Communications, senior author James Higham said their findings show that the changes in the monkeys' appearance had an evolutionary purpose, "to strengthen reproductive isolation between populations," ensuring the vitality of each species.
For sample images and other details, check this New York University press release.