WHEN ANTHROPOID BECAME HUMAN
WE HAVE passed in review, in the preceding chapter, the main series of events which led to the eventual evolution of the human, or pro-human stem. The series is cumulative as a whole and represents the more important genetic kinships that link mankind to the larger living world. However, the story of man's evolution is still incomplete for, as we shall see, the early pro-human types were essentially ape-like rather than human. The emergence of the pro-human stem, some sixteen to twenty-five million years ago, marked merely the beginning of the strictly human trend. This important trend, initiated by the final separation of the pro-ape and pro-human stocks, could lead to the human type only by running its natural course. By far the larger part of the time that has since elapsed was consumed in further evolutionary changes before a being that might properly be called human came into existence. The pro-human stock had effectively entered into a new life zone by remaining on the plains and plateaus as the forests receded. Their refusal to leave the ancestral home amounted in the end to an adaptive radiation from an aboreal to a terrestrial habitat. This course of events brought into active play the forces of natural selection in the evolution of more or less fundamental structural adaptations to meet the new environmental conditions. The trend set up by such a major shift in habitat is likely
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Publication information: Book title: The Evolution of Human Behavior. Contributors: Carl J. Warden - Author. Publisher: The Macmillan Company. Place of publication: New York. Publication year: 1932. Page number: 67.
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