[SunkenCiv]

Good question, and it’s difficult to imagine any evidence that could possibly answer that conclusively. As soon as fire was found to be useful, it probably happened. The alternative appears to be, that for 100s of 1000s of years, the earlier hominim types were carrying it from a natural source, and/or keeping it stoked once it was in the desired place.

[Alas Babylon!]

And that's the whole premise for this movie from 1979:

Rated R because Tommy Chong's daughter, Rae Dawn, was starkesss nekid through the whole thing.