Evolution Diary

For humans, the eyes are more than just windows to the outside world. They are also portals inward, providing others with glimpses into our inner thoughts and feelings.

Of all primates, human eyes are the most conspicuous; our eyes see, but they are also meant to be seen. Our colored irises float against backdrops of white and encircle black pupils. This color contrast is not found in the eyes of most apes.

According to one idea, called the cooperative eye hypothesis, the distinctive features that help highlight our eyes evolved partly to help us follow each others’ gazes when communicating or when cooperating with one another on tasks requiring close contact.

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