system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Where do all the massive amounts of bones and skulls come from in major catacombs such as the ones in France and why did people use these catacombs instead of conventional graves?
gpt
They didnt get put in the catacombs right at death.  They'd get buried first, but graveyard space was limited and when people were buried, it wasn't for forever.  After a few years, those people were dug up and their bones were put into the catacombs for long term storage.  So when you see the massive numbers of skulls and bones, that came after this was done for decades or even centuries.