52:2.9

The races are purified and brought up to a high state of physical perfection and intellectual strength before the end of this era. The early development of a normal world is greatly helped by the plan of promoting the increase of the higher types of mortals with proportionate curtailment of the lower. And it is the failure of your early peoples to thus discriminate between these types that accounts for the presence of so many defective and degenerate individuals among the present-day Urantia races.