Exactly! Some level of social structure is evolutionarily adaptive.

The specific expectation that women are responsible for crumbs on the counter is not itself natural. The process through which that expectation came to be is natural. The process through which social expectations arise is natural. The emergence of social expectations within a population is, as you say, evolutionarily adaptive. No particular expectation is more natural than any other. Different expectations will arise among different populations as their members interact collaboratively in adjusting to differing environments.

The same process unfolding in different environments produces different results.

How would populations become organized into societies if their members were not predisposed to organize? If the predisposition to interact is not a result of evolutionary forces, then of what is it a result?