How did people grind rice in ancient times? (Curious)

But what happened before there were stone mills?

I'm not into archaeology :) (the following is speculation, disagreements are welcome)

But there wouldn't have been stone mills in matrilineal societies (if there were any). Even in the late Neolithic, it's hard to imagine that large stone mills and grinders could have been made. The reason for this is that the stone mills would have to be large enough, since they were working by the weight of the mills.

Comparing the pounding of rice and the milling of rice, it can be seen that the milling of rice was a continuous work and was significantly more efficient than the pounding of rice. If there were mills first, there wouldn't have been any rice pounding :) At the very least, rice pounding wouldn't have been so widely used.

Especially with the advent of the water pestle. Using the principle of leverage, a very small head (elevation) of water is possible. And water power to turn a stone mill seems to require a much greater water power to push the water wheel blades! Not very realistic.