A child may be very like its mother in appearance, yet the quality is the father's. For instance, if the father is very generous, and the mother is finer, the child will perhaps be both generous and finer. In this way the evolution of the world goes on by the intermingling of nations and races. Those families who keep themselves segregated in the end become weak and very stupid. For this reason the Prophet in Islam allowed all races and castes to intermarry, because the time had come for the human race to evolve in this way. When a child is different from both its mother and its father, this is partly because of its heritage from other ancestors on either side, but also because of its astral impressions. Besides every thought, speech, and action of the child builds its self from the moment of its birth upon earth. It is for this reason that there can be such a difference between father and son, while there is no difference between fleas or mosquitoes of East and West.