Over the course of my life I have seen several large, dangerous fires. Unfortunate animals often perish in these. Especially slower ones, such as turtles. Surely, it can not have been difficult for humans to invent cooking in the broad sense - that is heating food by fire - over the course of a few millennia.
Now, boiling food should be an entirely different question, a mental leap that I don't see as obvious at all, nor do I think it likely to occur by accident. So, what are some early archeological clues for humans doing it?
I realise, it might be difficult to find archeological evidence, but implements, such as pots, spoons or tripods for placing such on the fire are probably very old. One text that made me think archaeologists might know much more than I imagined, was Native American Cookery. Said article contains the passage:
Boiling could be done in skin or bark utensils, or even on a clay bed, by filling with cold water, dropping in the meat and then heating with hot stones taken from a near-by fire. It was safer to boil in a bark dish than in a clay pot, because of the ease with which the pot was broken. One hot stone gives off a great deal of heat, and a dozen or so used in this manner soon finishes the task of hot-stone cooking.
If this applies generally, or many people used their kettles for pot roasting, we might have great difficulty finding these implements or establishing their use. Yet, shapes, materials or grease traces, might tell archaeologists much more than they would tell me.
Even if our estimates have to be very conservative, I am still interested.