Humans, chimpanzees and bonobos share eye patterns

Bonobo, eyes
iStock-Jeff McCurry

 Scientist have detected the same eye patterns in humans, chimpanzees and bonobos despite contradictions from previous studies.

Scientists have shown that the contrast between the white of human eyes, the sclerae, and the iris allows others to tell the direction of our gaze. Such ability allows humans to commence social learning and other social skills.

However, the sclerae of an ape’s eye is often much darker than the humans’, leading scientists to believe their gaze is hidden, meaning that apes would not be able to see where the other apes are looking.

Scientists from the National University of Singapore (NUS) as well as collaborators from the University of St Andrews and Leiden University, have conducted research that has led to a new discovery. Doctoral student Mr Juan O. Perea-García and Associate Professor Antónia Monteiro from the Department of Biological Sciences at the NUS Faculty of Science, have discovered that ape eyes possess the same pattern of colour differences as human beings.

The study discovered that bonobos, like humans, have paler sclerae and darker irises. However, chimpanzees have been found to have a different pattern. Chimpanzees have a very dark sclerae and paler irises. Although they are so different, both species have the same type of contrast seen in the human eye.

“Humans are unique in many ways, as no other animal can communicate with similar intricate language or build tools of such complexity. Gaze following is an important component of many behaviours that are thought to be characteristically human, so our findings suggest that apes might also engage in these behaviours,” said Mr Perea-García.

“We know that some gorillas and orangutans have eye colouration like our own, and some members of these species have eye colouration similar to the chimpanzees, but why is there this variation within a species? We are working with several zoos to find out more,” shared Mr Perea-García.


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