JAMB - Biology (2000 - No. 5)
The most recently evolved structure in animals is the
hair
cilium
scale
feather
Explication
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The earliest known evidence of hair is whiskers on therapsids, which were mammal-like reptiles that lived around 290 million years ago. Therapsids are considered the ancestors of modern mammals.
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Hair is a defining biological characteristic of all mammals. However, some species have evolved to have so little hair that they appear nearly naked.