Evolution provides no evidence for the sharp left turn

Hi Quintin,

Just wanted to say I thought this quite informative. Thanks!

It seems to me that humans have had (at least) two sharp left turns:

• behavioral modernity: humans rapidly (compared to the pace of early human evolution) become vastly more capable than other hominins
• the neolithic revolution and everything after: complex agricultural societies rapidly (compared to the pace of early human cultural change) become vastly more capable than other human groups

You've offered a plausible account of the development of behavioral modernity - but why do we get another qualitative jump in capabilities once we get enough behaviorally modern humans together? I suspect the answer hinges more on high-level facts about human intelligence than the specific mechanisms that brought it about. If so, then worrying about analogous developments in AI is appropriate.