Thirty years ago lay observers began to note differences in central France between the people of the mountains and of the plains. As early as 1868 Durand de Gros noted that in Aveyron, one of the southern departments lying along the border of a mountainous area, the populations of the region thereabout were strongly differentiated. On the calcareous plains the people were taller, of light complexion, with blue or blue-grayish eyes and having fine teeth. In the upland areas, of a granitic formation, the people were stunted, dark in complexion, with very poor teeth. These groups used distinct dialects. The peasants differed in temperament. One was as lively as the other was morose. One was progressive, the other was backward in culture, suspicious of innovations. This same observer noted that the cattle of the two regions were unlike. On the infertile soils they were smaller and leaner, differing in bodily proportions as well. He naturally, therefore, offered the same explanation for the differences of both men and cattle—namely, that they were due to the influences of environment. He asserted that the geology of the districts had affected the quality of the food and its quantity at the same time, thereby affecting both animal and human life. When this theory was advanced, even the fact that such differences existed was scouted as impossible, to say nothing of the explanation of them. As late as 1889 I found a German geologist, in ignorance of the modern advance of anthropology, strongly impressed by these same contrasts of population, and likewise ascribing them to the direct influence of environment as did the earlier discoverer. These differences, then, surely exist even to the unpracticed eye. We must account for them; but we do it in another way. The various types of population are an outcome of their physical environment. This has, however, worked not directly but in a roundabout way. It has set in motion a species of social or racial selection, now operative over most of Europe. This process it is our province to describe in this paper.
Before we proceed to study the French people, we must cast an eye over the geographical features of the country. These are depicted in the accompanying map, in which the deeper tints show the location of the regions of elevation above the sea level. At the same time the cross-hatched lines mark the areas within which the physical environment is unpropitious, at least as far as agriculture—the mainstay of economic life until recent times—is concerned.
A glance is sufficient to convince us that France is not everywhere a garden. Two north and south axes of fertility divide it into three or four areas of isolation. These differ in degree in a way which illustrates the action of social forces with great clearness. Within these two axes of fertility lie two thirds of all the
