DARWIN-WALLACE CENTENARY—DE BEER 349 
man’s estimation, the beautiful. Is it possible to doubt that just as we 
approve and delightedly revel in the beauty created by ‘natural selec- 
tion,’ so we give our admiration and reverence, without question, to 
‘goodness,’ which also is the creation of Nature’s great unfolding?” 
In many of the higher animals, parental care and self-sacrifice, in the 
interest of other members of the family such as incubating or gravid 
females and young, have been favored by natural selection and con- 
ferred benefit on the species. From earliest human times, the survival 
value of altruistic behavior has been enhanced because of the pro- 
longation of childhood and the consolidation of the family that have 
characterized the evolution of man. The size of the unit within which 
altruistic behavior conferred survival value has grown progressively 
larger, but fitfully, as history and anthropology have shown, from the 
family to the clan, the tribe, and the nation. In this manner, ethical 
standards of conduct and morality have arisen which can be seen to 
develop in individuals and have been seen to evolve in societies. Be- 
tween these units, competition on the subhuman level of natural selec- 
tion has persisted. With the development of man’s higher mental 
faculties, conscious choice and purposiveness became factors in evolu- 
tion, and for this reason the subsequent evolution of man has been of 
a nature different from that of other organisms because it was no 
longer governed solely by natural selection. 
NATURAL SELECTION IN ACTION 
Natural selection can be seen to be at work here and now in direct- 
ing evolution. Modern techniques of study of genetics in populations 
in the field developed by T. Dobzhansky and E. B. Ford have shown 
that the relative longevities of variants in different environments can 
be directly measured, and that the effects of such differential mortality 
have been to produce evolutionary change. An example of this type 
of research is that of H. B. D. Kettlewell on “industrial melanism” 
in moths. Up to 1850 the British peppered moth existed in its typical 
gray form known as Biston betularia, which is remarkably well 
adapted to resemble the lichens on the bark of trees. From that date 
a dark melanic variety appeared, known as carbonaria, which is ex- 
tremely conspicuous against the natural bark of trees. The melanic 
variation is controlled by a single dominant Mendelian gene and is 
slightly more vigorous than the normal gray type. Nevertheless, be- 
cause of its conspicuous color the carbonaria variety was constantly 
eliminated, and this variety persisted in the populations of the 
peppered moth only because the same mutation kept on occurring 
again and again. The industrial revolution brought about a marked 
change in the environment, since the pollution of the air by increasing 
quantities of carbon dust killed the lichens on the trees and rendered 
