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elegantbuffalo:

The bones of your middle ear were once part of a mammalian ancestor’s jaw.

The lower jaws of modern mammals have just one bone: the tooth-bearing dentary. Reptiles, by contrast, also sport smaller bones where the jaw meets the skull. As mammals evolved, the smaller, post-dentary bones shrank to form the tiny bones of the middle ear.

(Clade from Berkeley’s Understanding Evolution page)

wizard