INTRODUCTION TO SOCIOLOGY 89
Certain climates, especially the humid and warm, favorable to a vegetable nourishment in relation to the nutritive life and chiefly muscular activity of primitive peoples, seem to have been the most advantageous environment for the formation of rudi- mentary societies. Whatever may be the action of the geo- graphical structure, or the influence exercised by climate, or the variations of the human species, the latter belong to a type automatically and psychically uniform. It is, necessarily, from the mental and social point of view that its variations will be accentuated, its factors being the highest specialized and differ- entiated, and at the same time the least stable. But, on the other hand, by virtue of their complexity, they are also the most modifiable, being of such a sort that the result of the progress of civilization ought, naturally, to be the establishment of a higher level of progress with variations more multiplied, but also more feeble in intensity.
What was the location of the cradle of humanity; did its site depend solely upon climate? Has there been a single place of origin, or have there been various times and places? This question is hanging between the monogenetic and polygenetic hypothesis.
That which is important for positive science is to investigate what has been, in all cases, the necessary conditions for the appearance of man on the earth. This investigation can help in solving the controversy.
We now know that there exists a correlation among the following four factors: (i) The human dental system; it is analogous to that of the anthropoids. Primitive man was chiefly frugivorous. (2) The alimentary system, vegetarian. (3) The environment; the humid semi-tropical regions were the most favorable to an abundant vegetation. (4) The pre- dominance of the muscular life over the primitive nervous and intellectual life; muscular life does not require food essentially nitrogenous. All these correlative, primitive, social conditions and types are still met with in the semi-tropical and tropical zones, especially in maritime regions.
In going toward the temperate zones, man becomes more
