[brownbat]

You can combine many of these...

Several early inventions were incredibly time consuming to make by hand, and judging from apes, social groups didn't have a concept of specialization, but all sat around making and teaching the same thing at the same time, partially as a form of bonding. So, say, sharpening rocks improved consistent access to food, but lowered free time required to experiment or make other inventions, and doing the latter would exclude you from the social bonding of making the one tool, which risks making you an other the group resents. Lack of storage, even on clothing, meant everything after your first tool was disposable. Keeping things more than a day might have been an unnatural concept too, so already expensive production costs are multiplied by uses.

There was a long term observational study of chimps where a subgroup of them started spontaneously team hunting, chasing prey towards the others, like a set sports play. They did it effectively for a few seasons, then just stopped... Group dynamics changed and some left the tribe, others had mates, priorities just changed. Maybe retaining knowledge is really hard before you're organized around shared knowledge as a principle.