[@Muttonhawk] et al., about fire. Flints only produce sparks when struck against iron or a related substance. They do this because the hard flint shaves off tiny, tiny flecks of iron, and that iron (hot from being rubbed against the flint, and with an enormous surface area to volume ratio) oxidises violently in the air, making sparks. Flint-on-flint won't do it. You'll need the right kinds of rock.

If you really think fire is a good idea very soon, I can have it be invented and proliferated in my next post. Teknall is probably a few years behind everyone else at this point (he can catch up in my next post), so it works retroactively.