HERMANN J. MULLER 
own niches, in consequence of all of them alike having been 
products of a natural selection that got them here contempora- 
neously. This doctrine resembles in principle the cultural 
egalitarianism that some anthropologists apply to all coexisting 
human societies. In both cases two major points have been 
disregarded. ‘These are that evolution proceeds, under different 
circumstances and for different groups, at very different speeds, 
and—more important—that it varies greatly in the degree to 
which it is progressive. As Julian Huxley has often empha- 
sized2,3, the concepts of “‘progress’’, and of “higher” and 
‘““lower’’, as applied to biological evolution, correspond with 
objective realities. 
The higher forms, those resulting from the more progressive 
evolution, have elaborations that allow them to overcome more 
and greater natural difficulties, and even to turn more refrac- 
tory circumstances to their actual advantage. True, their weight 
of extra accoutrements tends to keep them from carrying out 
the easiest tasks so readily, and niches are thereby left in which 
the more primitive or lower forms can continue to thrive also. 
Nevertheless, the higher forms, by virtue of their more advanced 
capabilities, are on the whole more likely than the others to 
succeed in adapting to even more difficult situations in the 
future. That is, they tend, at least in their heyday, to have 
superior evolutionary potentialities, and thus to constitute stem 
forms for further advances. This is another illustration of the 
principle: “to him that hath shall be given”’. Yet even among 
higher organisms it is a rare species that succeeds in putting 
forth new shoots that persist long and develop much further; 
it is far more likely to enter an evolutionary cul-de-sac, as the 
fossil record attests. 
THE DIRECTION TAKEN HITHERTO BY NATURAL SELECTION IN MAN 
In the line of ancestry that led to man, and in his further 
biological ascent, the already existing genetic constitution con- 
ferred unusual faculties of manipulation, co-operation, com- 
munication and general intelligence, along with a posture that 
facilitated their use, and these faculties, working in conjunction, 
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