A foundation devoid of ethical content is no foundation at all.
And ethical is what works best with man's interaction as a society. As I said, religious ethics and morality are simply what man had already figured out codified into religion, so religious ethics and morality have no extra standing above anything Darwin would say.
If 'nature' is all there is, how can the 'basics' of matter in motion not apply? What else is there? Naturalistic assumptions will not permit anything other than the basics of particles of matter and energy. Darwinism insists on thoroughly naturalistic explanations based on material causes, doesn't it? Since naturalism assumes that everything in existence is the result of natural causes, that includes the chemical fizz you refer to as thoughts and feelings.
And ethical is what works best with man's interaction as a society.
Darwin purported to provide a naturalistic explanation for the emergence of morality. A claim of what is "best" assumes a moral standard by which society can be judged, which assumes the very thing in question. Morality cannot be explained simply by positing a prior moral rule since morality is what is supposed to be accounted for in the first place.