How did social darwinism give a false justification for imperialism?

[Jeffrey s]

Espreses's first two sentences are essentially correct. Social Darwinism was an attempt by people like Herbert Spencer and Francis Galton, but not Darwin himself, to apply Darwinian ideas about natural selection to human society. In other words, the Social Darwinists believed that certain people, and certain societies or civilizations, rose to the top of the human pecking order because they were better evolved.

Because of this, these people or societies were even justified in imposing their beliefs on other, "less enlightened," people. We see this in the "white man's burden" ideas of the British Empire, and even the tendency of the US to try to spread its beliefs about the merits of free-market democracy in places like, say, Iraq. Of course we see the concepts of the Social Darwinists carried to their logical extreme, as espreses points out, in the racial and cultural ideas of the Nazis.

Unfortunately, espreses follows his first two reasonable, factual sentences with ones that are obviously a reflection of his ideology. Darwin's ideas about the evolution of species through natural selection, while somewhat modified since the 19th Century, form the basis of modern biological thought. Far from being consigned to the ashbin of history, as espreses asserts, Darwinism has only received greater support with the development of sciences that did not even exist in Darwin's day, such as genetics, microbiology, and biochemistry.

One can always debate the merits of any theory. In fact the essence of science is just this openness to revision as new data or arguments become available. For instance, Newton's theory of gravitation was modified by Einstein, and recent work has led to thinking that Einstein's ideas on the subject may need to be modified, as well. One may accept Darwin's ideas or not, but to suggest, as espreses does, that no educated person accepts Darwin's ideas today is just simply not true. Espreses may not accept these ideas, but the vast majority of biologists, and scientists in general, do.