Which movement, whose development paralleled but was essentially independent of realism, based its aesthetics on nature, particularly on humanity's place in the (darwinian) environment?

I believe the answer is: Naturalism

Naturalism refers to the principle that believe that natural forces are the only one that exist and operates in our world.

Naturalism faced a direct confrontation with many religious groups because naturalists conveyed that the belief held by religious groups on how things happen in our nature are bogus.