My idea about that is that people had far fewer fields of endeavour to express themselves in, and yet they had the same cranial volume and brain complexity as w

My idea about that is that people had far fewer fields of endeavour to express themselves in, and yet they had the same cranial volume and brain complexity as we do today, and societies were also relatively similar in patterning (but I guess smaller in size and complexity than today), basically we had similarly complex mental and emotional lives back then as now, but Language was one of the few ways people could actually express all of that "stuff" that now comes out in so so so so many creative ways: the trillion fields of formal and informal endeavour we now have (actuarial science, chemistry, TikTok creators, professional YouTubers, e-sports, parkour, commenting on HN, creating RFCs, creating web standards, programming, East Asian studies, film, music composition, sports medicine, comparative mythology, life hacking, race studies, and so on and so on and so on....) As a result Language was heavily over-engineered back in the day when it was one of the few ways people could get all that "out".