178. The Time of the Peopling of America
About the end of the Palæolithic or beginning of the Neolithic some of these proto-Mongoloids drifted from Asia into North America. These were probably the real discoverers of the New World, which they found inhabited only by brutes. The time of their invasion can be but roughly fixed, yet within its limits it seems fairly reliable. Had the migration occurred much later, when the Neolithic was already well under way, the domesticated animals and plants of the Old World would have been introduced—cattle, pigs, sheep, wheat, barley, rice, millet, all of which the Americans lacked. The same holds for inventions like the wheel.
Analogous arguments weigh against a belief in a possible earlier peopling of America, say in the middle Palæolithic. In that event there ought to be cave or rock shelter or river terrace deposits corresponding to those of Europe in containing only implements of Palæolithic type. But none such have been found in America, or where alleged, their circumstances have remained matters of controversy.
Further, if Palæolithic man had inhabited the western hemisphere, it is likely that his fossil remains would have come to light. There has been much excavation, and numerous investigators are alive to the importance which evidence of this sort would bear. Yet to date not a single human fossil of positively Pleistocene age or type has been discovered. Numerous sensational finds have been announced. But in every case their geological matrix or stratum has been proved either recent or open to doubt. And not a single fragment of a skeleton of Neandertal type, or one equally different from modern man, is on record from America. Every once alleged Pleistocene skull or part appears to belong to some branch of the American Indian race as it exists to-day. It is therefore unlikely that man reached America before the last stage of the Palæolithic.
If the date of the entry is set at ten thousand years ago, the elapsed period accounts very well for the present diversification of the American race. There are broad and narrow headed tribes, tall and short ones, some with hooked noses, others with slightly wavy hair. But the fundamental type is everywhere the same. The differences seem just such as environment and mode of life, the accidents of descent from small groups, and perhaps a slight effect of selection, would be certain to accomplish in time. In general, the natives of America are remarkably homogeneous, considering the vast territory they occupy, its variations of temperature, humidity, altitude, and food supply, and the marked differences in the living customs of many tribes. The one group that at all stand apart are the Eskimo; and these are distinct in language and culture also. Moreover, they occupy the parts nearest to Asia, including both sides of Behring Strait. Thus they seem to represent a separate origin. But all the other groups from Alaska to Patagonia are so closely related somatically, that no comprehensive and generally accepted sub-classification of them has yet been possible. In fact, the American race seems almost too undifferentiated to require ten thousand years for its superficial diversifications; until it is remembered that human races left to themselves seem in most cases to alter rather slowly. Mixture is one of the greatest factors of racial change, and in the isolation of America this element was eliminated to a much larger extent than in most of the Old World.