EVOLUTION AND MAN 
Several Human Races Likely to Merge and Form One Great Hybrid Race in the 
Future—Variation Thus Created Will Present Many Possibilities to 
Eugenics—What Eugenics Can Do at the Present Time 
Maynarp M. METCALF 
The Orchard Laboratory, Oberlin, Ohio 
HANGE of emphasis is as char- 
¢$ acteristic of scientific thought in 
its progress as is change of style 
in clothes. Today genetics has 
the stage. A generation ago biologists 
were discussing evolution. A half gen- 
eration later the strenuous discussion 
as to the inheritance of acquired charac- 
ters was just closing with a recognition 
of the lack of evidence in favor of such 
inheritance. Natural selection became 
dominant ; sexual selection being increas- 
ingly questioned except among human- 
kind. Orthogenesis was generally ac- 
cepted as of some moment. 
This idea, however, of definite trends 
in evolution (orthogenesis) secured less 
attention than it deserved until the 
discussion of the inheritance of acquired 
characters became less absorbing. It 
was then that the abundant paleonto- 
logical evidence of evolution by minute 
changes, too minute to be of ‘‘selection 
value,’ came to be recognized not as 
establishing the inheritance of the effects 
of use and disuse, but rather as indi- 
cating the presence of trends of variation 
in particular directions. It even became 
evident that these trends in definite 
directions might produce hurtful results, 
even leading to the extinction of species. 
The huge saurians developed to such 
size that their very bulk aided in their 
extinction. The trilobites, so prominent 
in many fossil faunas, became extinct 
after a development which culminated 
in most bizarre forms, so eccentric as 
probably to indicate an unbalanced 
condition physiologically as well as 
structurally. To the paleontologist it 
is clear that in a number of groups of 
animals the highly evolved forms have 
1 This does not imply that many less-developed forms have not perished also. 
ment is not the only cause of extinction. 
356 
become extinct, the several groups being 
represented today by forms much 
simpler than many that have perished 
and perished very likely because of 
overdevelopment.! The minute changes 
in the structure of the feet and in the 
ridges of the grinding teeth in the horse, 
familiar to anyone who has read any 
book upon evolution, cannot by any 
stretch of the imagination be regarded 
each as of such value to their possessor 
as to have determined his survival in 
the struggle for existence. A better 
example of orthogenic change, showing 
inherent trends, could hardly be given. 
And these changes are not step by step 
related to utility. Indifferent for long 
geologic periods during their gradual 
development, they have now, however, 
culminated in a condition of specializa- 
tion so extreme as to threaten the 
extinction of the horse. Only domesti- 
cation saves him. The horse is a most 
grotesque, outlandish animal, a one-toed 
beast with a head as long as a barrel, a 
stiff inflexible animal that can’t even 
lie down, much less roll over, without 
an awkwardness beyond belief, if we 
had not seenit. Only familiarity breeds 
respect for the horse. He has a stiff, 
unplastic quality, is overspecialized 
until he can fit into only a very narrow 
field in nature, living in herds upon open 
plains. Man’s spread over the earth 
has produced a change in environment 
to which the horse could never adapt 
himself unaided. Indeed, barring the 
effects of domestication by man, the 
whole great group of the Ungulates is 
on the same road to extinction which the 
Dinosaurs have traveled before them. 
The destructive effect of evolution is a 
Over-develop- 
