In social terms, I equate nature with the wilderness (in which case the natural is opposed to the artificial). Metaphysically, nature includes everything, but that metaphysical concept is a crude instrument. "Behavioural modernity" has to do with the advent of culture via language, art, and other kinds of symbol use.

I've written a lot on this. See, for instance, this recent article:

https://medium.com/philosophytoday/shakespeares-pantheistic-deflation-of-art-c2e3b23ee8d4?sk=29631d16426034a52bfd82de62ed5ad5