Evolution
See also: Evolution of cetaceansAll cetaceans, including whales, dolphins and porpoises, are descendants of land-dwelling mammals of the Artiodactyl order (even-toed ungulates). Both are related to the Indohyus, an extinct semi-aquatic deer-like ungulate, from which they split around 54 million years ago. These primitive cetaceans probably first took to the sea about 50 million years ago and became fully aquatic about 5–10 million years later. Their features eventually became adapted for living the marine environment. Major anatomical changes include streamlining of the body, the migration of the nasal openings towards the top of the cranium, the shrinking and eventual disappearance of the hind limbs, the modification of the forelimbs into flippers, and the growth of flukes on the tail.
Read more about this topic: Whale
Famous quotes containing the word evolution:
“The evolution of humans can not only be seen as the grand total of their wars, it is also defined by the evolution of the human mind and the development of the human consciousness.”
—Friedrich Dürrenmatt (1921–1990)
“By contrast with history, evolution is an unconscious process. Another, and perhaps a better way of putting it would be to say that evolution is a natural process, history a human one.... Insofar as we treat man as a part of nature—for instance in a biological survey of evolution—we are precisely not treating him as a historical being. As a historically developing being, he is set over against nature, both as a knower and as a doer.”
—Owen Barfield (b. 1898)
“What we think of as our sensitivity is only the higher evolution of terror in a poor dumb beast. We suffer for nothing. Our own death wish is our only real tragedy.”
—Mario Puzo (b. 1920)