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 (19211990)
“The more specific idea of evolution now reached isa change from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity, accompanying the dissipation of motion and integration of matter.”
—Herbert Spencer (18201903)
“Historians will have to face the fact that natural selection determined the evolution of cultures in the same manner as it did that of species.”
—Konrad Lorenz (19031989)