Evolution
Hair has its origins in the common ancestor of mammals, the Synapsids, or possibly a subclade, the Sphenacodontoidea, about 310 million years ago. It is currently unknown at what stage the synapsids acquired mammalian characteristics such as body hair and mammary glands, as the fossils only rarely provide direct evidence for soft tissues. An exceptionally well-preserved skull of Estemmenosuchus, a therapsid from the Upper Permian shows smooth, hairless skin with what appears to be glandular depressions. The oldest known fossil showing unambiguous imprints of hair is the Callovian (late middle Jurassic) Castorocauda, an early mammal. The more advanced therapsids could have had a combination of naked skin, whiskers and scutes. A full pelage likely did not evolve until the therapsid-mammal transition. The more advanced, smaller therapsids could have had a combination of hair and scutes, a combination still found in some modern mammals, such as rodents and the opossum.
Read more about this topic: Evolution Of Hair
Famous quotes containing the word evolution:
“The evolution of a highly destined society must be moral; it must run in the grooves of the celestial wheels.”
—Ralph Waldo Emerson (1803–1882)
“The evolution of sense is, in a sense, the evolution of nonsense.”
—Vladimir Nabokov (1899–1977)
“As a natural process, of the same character as the development of a tree from its seed, or of a fowl from its egg, evolution excludes creation and all other kinds of supernatural intervention.”
—Thomas Henry Huxley (1825–95)