How did they figure out that seeds are, well, seeds? They were careful observers, probably of their own latrines -- seeds are often sources of food, but sometimes the plant is just eaten whole, and the seeds would be observed to sprout. This fits with my favorite anthropological idea -- that most of our major arts and inventions came from teenaged boys foolin' with stuff, or trying to gross each other out, play pranks, or double-daring each other. And they'd be likely to carve all those naked women images as well.
While the men were out chasing animals, and no doubt trying to bag the largest mammoth of them all - and then getting into fights among themselves about which mammoth was bigger (”Oh yeah - well mine has bigger tusks!!”) - all the while waving their dicks around (again - who’s was biggest).....
The women left behind (and getting paid 30% less than the men, mind you) were peacefully figuring out a way to become less dependent on their brutish male counterparts. During their times of quiet observation and reflection they noticed the seeds that they could plant and the food they could grow.
From those early days of cultivation the women created civilization. Somewhere along there they invented beer, in order to keep the men subdued.
(I like your teenage boy version better!)
The reason people started farming is that children like flowers and planted them near the house where they were allowed to go. Then their parents noticed there was food right nearby.
Written by someone who planted okra because the plants are beautiful but thinks okra is one of the slimy things those boys used to gross each other out with.