New York University and University of Exeter's recent study shows that Old World monkeys have undergone significant evolution in appearance to avoid interbreeding with closely related and geographically proximate species.

William Allen and James Higham of NYU and Martin Stevens of the University of Exeter examined 22 unique faces of guenons in their study published on June 26 in the academic journal Nature Communications.

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According to the study, the Cercopithecini primate changed remarkably in their facial features to be able to avoid interbreeding among sympatric species that often travel, feed and sleep side-by-side.

Interbreeding, which may result in afflicted infertile offspring, stays an unwelcome possibility to these guenons-a group of more than two dozen monkeys native to the forests of Central and West Africa.

During the 80s, an Oxford zoologist named Jonathan Kingdon had attempted to explain the reason for the diverse facial appearance of guenons, showing markings such as differently colored eyebrow patches, ear tufts, nose spots and mouth patches. His hypothesis stated that sympatric guenon have undergone these changes to avoid the risks of hybridizing.

To test Kingdon's hypothesis that is merely based on observations with the naked eye, the researchers of this recent study used quantitative analysis through sophisticated methods including facial recognition algorithms that could identify and quantify detailed facial features.

For over 18 months, they collected photographs of nearly two dozen species of guenons in the zoos of the United States and the United Kingdom. They then employed what is known as the eigenface technique, which is used in the field of computer vision for machine recognition of faces, to distinguish primate features then determine whether the appearance of each guenon species was related to others or not.

Researchers then concluded their study from results suggesting that face patterns of guenon species have evolved to become more visually distinct from those sympatric species that they are at risk of hybridizing with.

TagsNew York University, Exeter University, Old World Monkeys, Cercopithecini, interbreeding