Last week’s New Scientist features an article by geologist Donald Prothero showing how evolution shows much more of a gradual progression than is popularly known. Especially striking is the way the “hammer and anvil” part of our ear has formed.
Mammals are descended from synapsids, which developed parallel to reptiles from the same ancestor. Part of a reptile’s jaw functions as its ear – it transmits sound to the middle ear. The fossil record shows the migration of this part of the lower jaw, as it retreats and shrinks, to become part of our hearing apparatus.