who came up with the idea of survival of the fittest
Survival of the fittest Herbert Spencer first used the phrase, after reading Charles Darwin's On the Origin of Species, in his Principles of Biology (1864), in which he drew parallels between his own economic theories and Darwin's biological ones: "This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called 'natural selection', or the preservation of favoured races in the struggle for life."[1]
Davis–Moore hypothesis The hypothesis is an attempted explanation of social stratification, based on the idea of "functional necessity". Davis and Moore argue that the most difficult jobs in any society are the most necessary and require the highest rewards and compensation to sufficiently motivate individuals to fill them. Once the roles are filled, the division of labour functions properly, based on the notion of organic solidarity advanced by Emile Durkheim.[1]