which here follows can only be a hypothetical one, as we have no witness of the whole process; but it is not to serve as a proof, only as an illustration. We make it as simple as possible, disregarding, for example, the influence which fishing could have had on primitive man.
So soon as primitive man possessed the spear he found himself in a position to hunt still bigger animals. His food was, up to then, derived principally from fruits and insects, as well as, probably, little birds and young birds; now he could kill even bigger animals; meat became, henceforth, more important for his food. The majority of the bigger animals, however, live on the earth, not in the trees; hunting thus drew him from his airy regions down to the earth. And further, the animals most chaseable, the ruminants, were but seldom to be found in the primitive forest. The more man became a hunter the more could he emerge from the forest in which primitive man was bred.
This account, as I have said, is purely hypothetical. The process of evolution may have been the reverse. Equally as the discovery of the tool and the weapon may have driven man out of the primitive forest to come forth into open grass land where the trees were farther apart, just as much might forces which drove primitive man from his original abode have been the spur to the discovery of weapons and tools. Let us assume, for instance, that the number of men increased beyond their means of subsistence; or that a glacial period, say the glacier of the central Asiatic mountain range sunk low down, and forced the inhabitants from their forests into the grass plains which bordered it; or that an increasing dryness of the climate even more and more cleared the forest, and caused more and more grass land to come up in it. In all these cases primitive man would have been obliged to give up his tree life, and to move about on the earth; he was obliged from now on to seek for animal food, and could no longer in the same degree feed himself from tree fruits. The new method of life induced him to the frequent
