80:3.9

These changes, while resulting in cultural advances, produced certain biologic retrogressions. During the previous hunting era the superior tribes had intermarried with the higher types of war captives and had unvaryingly destroyed those whom they deemed inferior. But as they commenced to establish settlements and engage in agriculture and commerce, they began to save many of the mediocre captives as slaves. And it was the progeny of these slaves that subsequently so greatly deteriorated the whole Cro-Magnon type. This retrogression of culture continued until it received a fresh impetus from the east when the final and en masse invasion of the Mesopotamians swept over Europe, quickly absorbing the Cro-Magnon type and culture and initiating the civilization of the white races.