everything. We hardly ever know the definite character of the struggle which occasioned the disappearance. The phrase is like the liturgical refrain of a litany, chanted over the fossils of vanished species. If the mere fact of dying out be sufficient proof of maladjustment to the environment, the explanation is reduced to a tautology. The importance of the doctrine of the struggle for existence depends on the assumption that living beings reproduce themselves in sufficient numbers of healthy offspring, and that adaptation to the environment is therefore the only decisive factor. This double assumption of prolificness and of healthiness is obviously not always true in particular instances. There are limitations to the doctrine of Malthus.
But there is another factor in evolution which is not in the least explained by the doctrine of the survival of the fittest. Why has the trend of evolution been upwards? The fact that organic species have been produced from inorganic distributions of matter, and the fact that in the lapse of time organic species of higher and higher types have evolved are not in the least explained by any doctrine of adaptation to the environment, or of struggle.
In fact the upward trend has been accompanied by a growth of the converse relation. Animals have progressively undertaken the task of adapting the environment to themselves. They have built nests, and social dwelling-places of great complexity; beavers have cut down trees and dammed rivers;
