Where and when the subjugation of the plant world began it is impossible to say. It very probably had its origin in the fertile open lands of the tropics. But that it originated in the central region of Africa, or that the agriculturists of that region were of native origin, are both subjects open to question. The forest folk may have spread into the open country, there developed a crude agriculture, favored the growth of food plants at the expense of useless shrubs and trees, and gradually advanced in this new form of industry. This would be in accordance with the opinion of Virchow, who looks upon the negro as the descendant of the Pygmy. No great change was necessary to convert the one into the other. The Pygmy is negro-like in cast of countenance and bodily formation. He differs in size, in complexion, and in shape of head. But new conditions may have given rise to these differences. The fierce suns of the African lowlands may well have caused an increased deposit of pigment, changing the yellowish hue of the Pygmy to the deep black of the negro. An increase in size is a natural result when exertion diminishes and food increases. And a tendency for the head to change from the short to the long shape is shown in the Bushmen. On the other hand, certain anthropologists, of whom we may name Quatrefages, take an opposite view, and believe that the negroes migrated from Asia or the Eastern islands to Africa, being, like the negro-like Papuans, descendants of the sable or dark brown Negritos of the East. In this case agriculture may have originated in Asia and have been brought by migrants to Africa. All we know historically concerning it is that the earliest traceable seats of agriculture appear to have been the fertile valleys of India, Babylonia, and Egypt. But the known culture of the earth in these regions goes back only a few thousands of years, while for the first crude stages of agriculture we must probably measure years by tens of thousands. The degree of subjection of nature to man's needs, as displayed in tropical agriculture, was comparatively small, and its effect on the development of the human intellect, while important, was limited. It had the highly useful result of a great increase in population, the growth of village and town life, an advance in social relations, and the beginning of political relations. New implements were needed, better houses were erected, the settled condition of the people gave rise to direct efforts at education, and added the important element of commerce, in its earliest form, to the industries of mankind. The result must have been a fresh start in the development of the intellect, though one that probably soon reached its culminating point in the central tropics.