Which organism developed eyes first? © Getty Images

Which organism developed eyes first?

Due to the sense's rapid evolution, there may have been more than one biological ancestor for sight.

Asked by: Chris Forshaw, Swindon

Advertisement

The evolution of the eye (which is actually an extension of the brain) was a gradual process, beginning with evolution of individual photosensitive cells. True eyes probably started with the development of photosensitive pits, such as those found in planaria (flatworms). There is evidence that snails in the Cambrian period, some 570 million years ago, possessed such pit eyes, but there may have been more than one biological ancestor for the subsequent rapid evolution.


Advertisement

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.