Answer:
The root: After Darwin published his theories on biological evolution and natural selection, the sociologist Herbert Spencer and other ideologists drew further parallels between economic theories and Darwin’s scientific principles.
The usages by Europeans:
By extending their arguments to address the entire world, some Social Darwinism's followers justified imperialism on the basis that the imperial powers were naturally superior and their control over other nations was in the best interest of human evolution. This is the theory that they used to justify the European annexation of Africa and Asia.
Explanation:
Social Darwinism is a loose set of ideologies that was based on Charles Darwin’s theory of evolution by natural selection. Social Darwinism's followers believe in “survival of the fittest”—the idea that certain people become powerful in society because they are innately better. The ideology has been used to justify imperialism, racism, eugenics and social inequality at various times over the past century and a half.