Well, they seem to have been thriving, are the oldest examples of copper tools, copper smelting, even bronze and, debatably, writing. And then, they suddenly went into decline and, over the course of some 300 years, basically vanished, with the tech, culture, and metallurgy going with them. It’s not entirely clear why, it was probably a mix of factors, but one hypothesis was that heavy metal poisoning contributed.

See, while they definitely did mine, smelt, and make things with copper, they’re usually considered a stone-age culture, partly because they mostly didn’t use copper for tools, instead using it for ornaments and decorating pottery. As you may imagine, using random ores to make pots, especially if you don’t know what you’re doing, especially when of them is cinnabar, isn’t the best of ideas.