I have to wonder just how well we really understood things back then. The implication that hunting a mastodon or a even deer was easy back then was easy given that they basically had to get close enough to them to reach by throwing stones. Or that farming was very work-intensive - maybe it wasn’t. Maybe the first crops actually did grow like weeds and all it took was planting the seeds in some treeless area and then coming back in 6 months. Things were a lot different then...what the grew, and what the enemies of those crops were.
no real mystery that they would notice new plants would spring up near the old plants, that they could dig up small plants and put them next to their homes.....
humans have always had the ability to learn.....