Asked by: Emre Yorgancıgil, Istanbul, Turkey
We have evolved eyelids to protect our eyes from drying out or getting scratched. When you are sleeping, it is dark anyway, so there’s not much point in your eyes being open. But your ears have evolved as an important early warning mechanism, allowing you to wake up if, say, there’s a tiger growling in the undergrowth.
Some animals, including seals, otters and hippos, can close their ears, but this is to keep water out while swimming.
Read more:
Subscribe to BBC Science Focus Magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun facts.
Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.
Subscribe to BBC Science Focus Magazine and try 3 issues for just $9.95
Discover our latest special editions covering a range of fascinating topics from the latest scientific discoveries to the big ideas explained.
Listen to some of the brightest names in science and technology talk about the ideas and breakthroughs shaping our world.
By entering your details, you are agreeing to our terms and conditions and privacy policy. You can unsubscribe at any time.