University of Texas Arlington

ARLINGTON - A UT Arlington anthropologist is gaining national recognition for a theory that climate change following massive volcanic eruptions drove Neanderthals to extinction and cleared the way for modern humans to thrive in Europe and Asia.

Assistant professor Naomi Cleghorn worked on a research team led by Liubov Vitaliena Golovanova and Vladimir Borisovich Doronichev of the ANO Laboratory of Prehistory in St. Petersburg, Russia. She is co-author on a paper published in the October issue of Current Anthropology. Stories about the research have recently appeared in The New York Times and on the USA Today and National Geographic News websites.

"[W]e offer the hypothesis that the Neanderthal demise occurred abruptly (on a geological time-scale) ... after the most powerful volcanic activity in western Eurasia during the period of Neanderthal evolutionary history," the researchers write. "[T]his catastrophe not only drastically destroyed the ecological niches of Neanderthal populations but also caused their mass physical depopulation."

Evidence for the catastrophe comes from Mezmaiskaya cave in the Caucasus Mountains of southern Russia, a site rich in Neanderthal bones and artifacts. Recent excavations of the cave revealed two distinct layers of volcanic ash that coincide with large-scale volcanic events that occurred around 40,000 years ago, the researchers say.

Geological layers containing the ashes also hold evidence of an abrupt and potentially devastating climate change. Sediment samples from the two layers reveal greatly reduced pollen concentrations compared to surrounding layers. That's an indication of a dramatic shift to a cooler and dryer climate, the researchers say. Further, the second of the two eruptions seems to mark the end of Neanderthal presence at Mezmaiskaya. Numerous Neanderthal bones, stone tools and the bones of prey animals have been found in the geological layers below the second ash deposit, but none are found above it.

The theory that climate change led to the Neanderthals extinction has been around for several years. The problem with that theory, however, is that the Neanderthals had survived several oscillations in environmental conditions in the past, Cleghorn said. Linking their extinction with a massive volcanic eruption makes more sense than tying it to a gradual climate change, the team believes.

"A volcanic event has a very rapid impact on the landscape," Cleghorn said. "The environment literally crashed at that point."

Cleghorn said her interest in the work stems from a desire to understand how these close cousins of modern humans could be wiped out.

The ash layers the team studied correspond chronologically to what is known as the Campanian Ignimbrite super-eruption which occurred around 40,000 years ago in modern day Italy, and a smaller eruption thought to have occurred around the same time in the Caucasus Mountains. The researchers argue that these eruptions caused a "volcanic winter" as ash clouds obscured the sun's rays, possibly for years.  The climatic shift devastated the region's ecosystems, "possibly resulting in the mass death of hominins and prey animals and the severe alteration of foraging zones."

Anthropologists have long puzzled over the disappearance of the Neanderthals and the apparently concurrent rise of modern humans. Was there some sort of advantage that helped early modern humans out-compete their doomed cousins? This research suggests that advantage may have been simple geographic location.

"Early moderns initially occupied the more southern parts of western Eurasia and Africa and thus avoided much of the direct impact of the ... eruptions," the researchers write.

While the researchers stress that more data from other areas in Eurasia are needed to fully test the volcanic hypothesis, they believe the Mezmaiskaya cave offers "important supporting evidence" for the idea of a volcanic extinction.

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