This is total speculation but I recall that in many of the old stories
and fabels there is a large container of stew or soup simmering away -
the water heated over fire with vegetables, herbs and pieces of meat
added to it. It warms you up when you're cold, the meat is loosened from
the bones and comes off easily, the nutrients, especially in the bone
marrow, are released and become part of the broth. Finally, it's a way
of incorporating much of what has been gathered and hunted into one big
pot that everyone can share ("scoop" from).

If you have a fire that you tend and keep going 24/7, it seems only
natural that out of curiousity you would experiment with heating up food
(and water), grinding up stuff with mortar and pestal, mixing different
things together...

Would this have been possible before there were clay pots? Would an
animal skin work?

- Francesca