A 300,000-year Neanderthal reign over Eurasia may have ended in dark skies. Researchers uncovered layers of volcanic ash that they say represents eruptions around the Caucasus region of southwestern Russia about 40,000 years ago -- just around the time when Neanderthal numbers began to fall and allow for the rise of modern humans.

Such suggestive findings come from the Mezmaiskaya cave in southwestern Russia, which shows evidence of Neanderthal activity up until the volcanic ash layer. Then the former cave inhabitants seemingly disappear without a trace.

That represents another piece of evidence for paleoanthropologists who believe that catastrophic eruptions led to a volcanic winter and wild climate changes that crippled the Neanderthal population in northern Eurasia. By contrast, the theory says, modern humans lived farther south at the time and would have been unaffected by the volcanoes.

The theory has not gone unchallenged, and the latest study won't settle the debate.

But it's another clue that may help decode the prehistoric disappearance of the Neanderthals.

Read full story at Scientific American.