370 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1958 
strong as a lion, and as hardy asa dog? If we had unrestricted power 
to plan the evolution of the human genotype we would probably equip 
it with all these qualities and some others besides. But natural selec- 
tion does not work according to any plan. Selection is opportunistic; 
whatever can survive does. Man’s evolution was not designed or 
arranged beforehand. It took the course which it did because man’s 
genotype, imperfect as it was, was good enough to survive, and in fact 
good enough to make our species a tremendous biological success. 
Specialization is a common feature of the evolutionary pattern in 
many kinds of organisms at the expense of all-around perfection. The 
former is evidently more easily achieved than the latter. This is true 
not only of unplanned evolution which occurs in the state of nature 
but also of evolution under domestication, which to some extent is 
planned. Among cattle, there exist dairy breeds and beef breeds; 
there exist also some unspecialized breeds, but no breed combines the 
maximal performances of the best dairy and the best beef breeds. Why 
this is so is hard to tell; it may be that a combination of the above 
sort is a physiological impossibility, since the qualities which one 
may wish to combine may be antagonistic. On the other hand, it may 
be that a perfect breed of cattle is simply yet to be obtained. 
Perhaps the most impressive example, other than man, of an 
organism whose biological success appears to be due to an outstanding 
development of just one ability, and a mediocre development of others, 
is the man-of-war bird (Fregata). Those who have had the oppor- 
tunity to observe these superb fliers procure their food from the tropical 
seas can hardly imagine a more perfect flying machine. Yet, the 
legs of these birds are so weak that they cannot rise into the air from 
a flat surface, nor can they alight on water since their plumage be- 
comes waterlogged. Man is certainly the best thinking machine which 
protoplasm has produced. This confers upon him a biological adapted- 
ness so great that he continues to prosper as a species despite his rela- 
tively weak body, his several biological disharmonies, and his many 
follies. He need not fear biological extinction so long as his genotype 
as a whole enables him to live in some environments, either “natural” 
or devised by his own ingenuity. 
EVOLUTIONARY PROCESSES ACCENTUATED BY CIVILIZATION 
Many traits that were essential for bare survival in a paleolithic 
culture are unnecessary in New York City, but we have emphasized 
that natural selection is not restricted to the struggle for survival. 
For all organisms, reproduction is the essential step in selection, and 
reproduction in man involves not only bearing children, but rearing 
them to maturity. In modern civilization, furthermore, parental in- 
fluence may often be decisive in determining the success of children 
