from them much less, having been made more resistant by centuries of natural selection.
This long discussion may now be summarized. We dealt with lethal selection, that form of natural selection which operates by prematurely killing off the less fit and leaving the more fit to survive and reproduce their kind. It is of course understood that the word "fit" in this connection does not necessarily mean morally or mentally superior, but merely fit for the particular environment. In a community of rascals, the greatest rascal might be the fittest to survive. In the slums of a modern city the Jewish type, stringently selected through centuries of ghetto life, is particularly fit to survive, although it may not be the physical ideal of an anthropologist.
Two forms of lethal selection were distinguished, one depending on starvation and the other on causes not connected with the food supply. Direct starvation is not a factor of importance in the survival of most races during most of the time at the present day so far as the civilized portion of the world is concerned. But disease and the other lethal factors not connected with the food-supply, through which natural selection acts, are still of great importance. From a half to two-thirds of all deaths are of a selective character, even under favorable conditions.