Probably melted down, but I suspect it's been long enough that they aren't an issue anymore.
One Strip! One Strip!Nah man. 4000 years is nowhere near long enough to get rid of that problem. How long exactly it would take depends on what specific materials we're talking about, but, well, Plutonium has a 24000 year half-life and that's one of the shorter-lived ones.
It's probably not a huge issue as long as you stay away from the meltdown sites, though.
Screw them.
What can they honestly provide?
The author had his chance to do something with them, and botched it.
One Strip! One Strip!An Q&A with Boichi
, with some interesting stuff. I didn't expect Senku's clothes to be made of leather. Where did he even learn to tan skin?
It's quite astounding to me that Boichi managed to have a successful career in Japan while barely speaking Japanese… He seems to be quite the reclusive artist though…
edited 30th Dec '17 8:59:13 AM by Lyendith
That does explain some things.
But it also means that the thing that turned people to stone was earth born.
One Strip! One Strip!I wonder how many people were in space, or if people survived in other ways. I remember hearing that you need ~150 people to create a population that won't eventually inbreed itself to death, and this seems like the sort of manga that would care about that sort of thing.
Does anyone actually read these?

…Shouldn't they all be cousins in this village, anyway? With only 40 people over at least 3 or 4 generations, there has to be some degree of consanguinity…
Also a bit of Fridge Horror: considering that everyone was turned to stone on the same day, what became of the nuclear power plants and other dangerous facilities that were no longer maintained…?