In general, adaptations do not involve the creation of new structures, but result from the modification of existing structures. Consequently, when adaptations are examined closely, they often resemble contraptions rather than examples of beautiful design. For example, the 3 middle ear bones in the mammalian ear are modifications of bones present in mammalian ancestors. The stapes is derived from a jaw support bone in fish ancestors. The malleus and incus are derived from the jaw joint bones in reptilian ancestors.

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