Explain the theories of social darwinism?

In essence, social darwinists wanted to apply certain rules and ideas that were true for biology as we know it today; natural selection, and 'survival of the fittest', to the whole level of society.

The issue with this idea is that, while, both of those ideas talk about certain phenomena of biological organisms in society, it is questionable whether one can make a direct translation to the societal and political level. What is more importantly, in their view of society, the capable and adaptable would see their power and wealth increase, while the incapable and weak would be eventually rooted out of society.