The way it is presented we were "not modern" and something caused us to become "modern". 
100,000 years is not a long time ago when compared to the amount of time since we split with the Neanderthals (600,000).

why 100k years ago ? it's not clear to me either.

based on tools ?

0xbitcoiner

after extended periods of stasis, the sophistication of manufacturing went up dramatically at about the same time that modern humans came along. So, whatever the barriers to cumulative culture existed in the past, it's clear that the brakes were off by 100,000 years ago.

science

When Did Humans Start Social Knowledge Accumulation ?

OK we know when, but why?

>after extended periods of stasis, the sophistication of manufacturing went up dramatically at about the same time that modern humans came along. So, whatever the barriers to cumulative culture existed in the past, it's clear that the brakes were off by 100,000 years ago.