64 evolution: the ages and tomorrow 



species. As the evolutionist sees it, man is not "radiating 

 adaptively." He has not built any bodily specializations. He 

 is, as was pointed out earlier in this chapter, depending on 

 his hands; and functionally, hands are exactly alike in all 

 the so-called races. Even in the recorded changes and minor 

 perfectings, like increasing round-headedness and vertical 

 posture, there are no true racial distinctions. What are con- 

 strued as races are statistical inferences from the individ- 

 ually inherited pattern of a common germ plasm. 



Genetically, man is one species; and the fact that he is one 

 of the most variable of all species does not alter that state- 

 ment. The chromosome record and interbreeding record 

 clearly shows complete germinal compatibility. There are 

 no mutually infertile groups in man. 



Genetically, man has had a peculiar history. The usual con- 

 ditions of isolation and variation produce new species, new 

 genera, new families. There is no question that man started 

 in the direction of species change immediately after his 

 origin some 1,000,000 years ago, but his rising intelligence 

 and restlessness drove him far afield. Many animals show 

 tendencies toward mass migration, but in man it becomes 

 an irresistible urge in the mass and in small groups. In his 

 later history, prompted by the desire to trade or discover or 

 find food or escape his enemies, he spread out all over the 

 world, so that now he is the most widely distributed species 

 on earth. 



The genetic differences encountered in the races of man 

 are all of rather minor proportions— mutations of a common 

 genetic complex. The cross between the Negro and the 

 white is an example. In color the cross produces a dilution 

 called mulatto and two pairs of genes only are involved. A 

 mating of two mulattos will produce shades from black to 

 white inclusive. An examination of the pigment producing 

 these shades reveals that a melanin substance is common to 

 whites as well as blacks— the identical pigment laid down in 

 varying degrees of concentration. In this instance there has 



