Scientists Say: Vestigial

This is a word used to describe something that once had a function but doesn’t anymore

Dogs can perk up their ears, but humans can’t. Why? The muscles we have to move our ears have become vestigial. They are still there, but they don’t work well.

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Vestigial (adjective, “Vehs-TIH-gee-uhl”)

This is a small, leftover form of something such as a body part or behavior that doesn’t have any function. If it’s a body part or organ, it might be much smaller than a functioning version in another species. Or it might only be partially developed.

For example, many mammals can swivel their ears, pointing them toward certain sounds. Humans can’t do that. Instead, we turn out heads. But we still have some tiny vestigial muscles around our ears. Those muscles are the leftovers of muscles our ancestors used to turn their ears. The only function those muscles serve now is as a party trick — when someone shows off by wiggling their ears. 

In a sentence

Tiny pumpkin toadlets have a vestigial call that they can’t hear.  

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Bethany is the staff writer at Science News for Students. She has a Ph.D. in physiology and pharmacology from Wake Forest University School of Medicine.

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