General idea:
Ever increasing interaction with/in nature -> idea that nature has a history -> evolutionary theories of nature - - -> humans evolve.

Darwin specifically:
He gave us the idea that everything in nature is adapted to its place,
but that this is the result of an on-going struggle for existence,
not given by creation once and for all.

This relates to and supports a dominant idea about social order, namely,
that one’s place in society is a result of a natural process of selection, and,
given that the result is adapted,
this is right/ justifiable/ as good as we could hope for.