When the World Was First Peopled
Much trustworthy evidence has been collected to show that the whole world had really been peopled during the period which roughly coincides with what is known in geology as the Ice Age; that is, when a large part of the northern and southern hemispheres was subject to invasions of thick-ribbed ice advancing successively from both poles. The migrations were most probably begun before the appearance of the first great ice-wave, then arrested and resumed alternately between the glacial intervals, and completed after the last glacial epoch, say, some two or three hundred thousand years ago.
At that time the various wandering groups had already made considerable progress both in physical and mental respects, as is seen in the Neanderthal skull, which is the oldest yet found in Europe, standing about midway between the Javanese ape-man and the present low races. All were still very much alike, presenting a sort of generalized human type which may be called Pleistocene man, a common undeveloped form, which did not begin to specialize—that is, to evolve the existing varieties until the several primitive groups had reached their respective homes as disclosed at the dawn of history.