156 THE AMERICAN JOURNAL OF SOCIOLOGY
and settled conditions, a gradual moderation of the powerful sexual impulses could reasonably be expected, and we might then hope for the growth of intellectual capacity even after the age of maturity.
In the past the negro race has shown no tendency toward higher development, except under the tutelage of other races; and, among the alien civilizations that have exerted a profound influence upon the African race, that of the Moslem Hamites and Arabs is the most important. Penetrating into Africa from the north by way of the Sahara, the cavalry hordes of the Hamites of north Africa succeeded in forming reasonably permanent states throughout the northern Sudan, and in influencing the native negro societies both physiologically and intellectually. The great principalities founded by the Fulbe in the Niger country, and by the Tuaregs in the region about Timbuctoo, are the most striking examples of this activity. The states thus founded belong to the feudal type; the agricultural negroes form the subject peasant class; while the Moslem invaders constitute a nobility of armed cavaliers. It admits of no doubt that the civilization of Africa has been improved by this conquest. The conquering tribes brought with them a written literature, and many industrial and domestic arts, which they imparted to the conquered races. Of course, this form of conquest was possible only in the regions where cavalry could penetrate; the dense primeval forests of Africa, where the tzetze fly renders the raising and keeping of horses impossible, set limits to the out-and-out conquest by Berber and Arab tribes.
This great forest region, however, the Arabs entered from the north and east as traders, and in so" doing they gave an entirely new and sinister meaning to African slavery. As beasts of bur- den cannot survive in these parts of Africa, the traders needed human carriers to convey their freight. Starting from some commercial town on the upper Nile, they would purchase a suffi- cient number of slaves to carry their wares into the interior. But the goods transported back, the rubber and ivory, necessitated a much larger number of carriers, so that a great demand for slaves arose wherever the traders penetrated. The chieftains of
