76 Proceedings of Indiana Academy of Science. 
One more important criticism of the narrow Darwinian interpreta- 
tion should be pointed out. Evolutionists in the last quarter of a cen- 
tury have come to see that the struggle so much stressed in the years 
immediately following Darwin’s life is by no means an unmitigated one, 
but that, on the other hand, those communities of animals that are most 
highly developed are the ones in which there is a division of labor and 
in which co-operation takes the place of bitter competition. Co-operation 
results in community prosperity and growth. This is the principle of 
mutual aid, and even a cursory examination of the facts of nature will 
show that it is not an unimportant one. It depends upon several obser- 
vations which may be easily verified. There is not a vast number of 
species of animals that lead isolated lives, but there are numberless 
species that live in societies which seem to have their raison d’etre in 
better means for defense, for securing food, or for rearing offspring. 
A fairly keen competition and warfare may often be noted between 
animals which are members of different classes or species, or even be- 
tween different tribes of the same species, but among individuals of the 
same community or tribe peace is the rule. And if an entire population 
is forced to struggle against the unfavorable conditions of drought, flood, 
famine, disease, wind or weather, the survivors, weakened by such a 
contest, can at best produce offspring with insufficient vigor to bring 
about the progressive development of the species. It is common knowl- 
edge that when a pestilence of any kind has swept an animal commu- 
nity, the remnant of the population is years in restoring its former 
numbers. Finally the degree of development of any group of animals 
is measured by the degree in which social life, co-operation for mutuai 
good, and division of labor obtain, with the corresponding avoidance of 
severe competition. The social species prosper, while many of the un- 
social ones tend toward decay. The principle of mutual aid presents 
another aspect of the story of development in the animal world which 
must not be overlooked, and shows that struggle is not in every case 
the chief characteristic of progress. This principle. doubtless does not 
deserve the rank of the chief factor in evolution given it by Kropotkin, 
one of its proponents; but neither does the struggle for existence deserve 
the prominence which the German Neo-Darwinians have given it. The 
isolated species of animals struggling against his kin, his neighbors and 
his physical environment cannot longer be locked to for the entire cause 
of progressive evolution; rather we must look to both the social and 
unsocial, and remember that probably no single factor is broad enough 
to account for all the complexities of animal development. 
These objections to and arguments against the Darwinian factor of 
natural selection, and especially the narrow Neo-Darwinian interpreta- 
tion of it, constitute abundant reasons why it cannot be accorded the 
chief, the all-important place in the progressive development of animals. 
