_Scheme of Geologic Time during the Age of Man in the Eastern Hemisphere._
{ Europe connected with Africa. { Man homogeneous. { Temperature mild. { Industry palæolithic with { 1. Pre-glacial. { African elephant in England. { simple implements. { { Tropical animals abundant. { Migrations extensive. { { { Language rudimentary. { Quaternary, { { Europe severed from { Man dividing into races. Diluvial { { Africa. { Industry palæolithic with or { 2. Glacial. { Temperature low. { compound implements. Pleistocene { { Reindeer in France. { Cave dwellings. Migrations Epoch. { { Arctic animals abundant. { limited; races in fixed areas. { { { Continents assume present forms. { Races completely established. { 3. Post-glacial. { Temperature rising. { Industry neolithic. { Temperate zones established. { Beginning of sedentary life. { Languages developed in classes.
{ Geographic conditions undisturbed. { Races develop into contact. { 1. Pre-historic. { Wild animals not diminished. { Industry of stone and copper. { Present { 2. Proto- { Conditions altered by agriculture. { Great migrations begin. or { historic. { Wild animals slain or tamed. { Industry of bronze and iron. Alluvial { Epoch. { { Geographic conditions greatly { Extensive mingling of races. { 3. Historic. { modified by man. { Development of nations. { { All lower animals subjugated.
According to the analogy of other organic beings, man would have been more impressible to his surroundings in the early history of his existence as a species, the young, either as an individual or a genus, being more plastic than the old. Furthermore, in his then condition of culture, or absence of culture, he had less to oppose to the assaults of his environment.
_Classification of Races._--It is not possible in the present status of the science of man to point out precisely how the various conditions of the great continental areas reacted on the homogeneous primitive type to develop the races as we know them. The same difficulty encounters us with other animals and with plants. We know, however, that at the dawn of history each of these areas was peopled by nations resembling each other much more than they resembled nations of any of the other areas.