What's the Bottom of a Jomon Pottery?

Jomon pottery is noted for having decoration s where, while the clay was still wet, impressions were made in the clay with ropes. There are some other very notable characteristics of these early pots - they tend to be very small and have round bottoms. And it makes you think, well, wait a minute, then, how were they using these pots later? So perhaps the earliest use of these pots was exclusively for cooking by hunter gatherers.