The Campanian Ignimbrite, a super-eruption in the Bay of Naples 39000 years ago, probably played a part. Most of the caldera is submerged under the sea, but there are still fumaroles, boiling mud pools and bradyseism in the area. It's an entertainingly dangerous place of the Yellowstone ilk. If it goes off again it won't be a few thousand Neanderthals, but the three million people in and around Naples who may be doomed.