The Dragons of Eden by Carl Sagan

Author:Carl Sagan [Sagan, Carl]
Language: eng
Format: epub
ISBN: 978-0-307-80100-5
Publisher: Random House Publishing Group
Published: 2011-06-21T16:00:00+00:00

A nest of Protoceratops eggs from the Cretaceous of the Mongolian People’s Republic.

Courtesy of The American Museum of Natural History

The immobilization hypothesis seems particularly apt in light of the evolution of mammals, who arose in an epoch dominated by hissing, thundering and altogether nightmarish reptiles. But nearly all reptiles are cold-blooded* and, except in the tropics, are forced into nocturnal immobility. Mammals are warm-blooded and able to function at night. The nontropical nocturnal ecological niches may have been almost untenanted in the Triassic Period, some two hundred million years ago. Indeed, Harry Jerison has suggested that the evolution of mammals was accompanied by the development of then extremely sophisticated (and now commonplace) versions of hearing and smell, senses for perceiving distances and objects at night; and that the limbic system evolved from the necessity of processing the rich array of data from these newly elaborated senses. (A great deal of the visual-information processing in reptiles is done not in the brain but in the retina; the optical processing apparatus in the neocortex was largely a later evolutionary development.)

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