^^^^^ CB; Yes, cooperation or sociality should be the number one. Our species name should be homo communis or socio, not homo sapiens ( intelligent). Language is fundamentally socially constituted and constituting. A critical thing to understand is that a major aspect of human sociality is social connects between living and dead generations. Lenguage is a major function in this cross generational connection. The prime human intelligence is social intelligence. The difference between human tool use and that of other species is that knowledge of tools is passed on and accumulated across generations as culture, language and custom. The wheel does not have to be reinvented.
Very interesting that this somewhat pro-cooperation hypothesis is spoken of favorably in "The Economist".