Neanderthals may have gone out with a bang.
At least three volcanic eruptions 40,000 years ago devastated Neanderthals' homelands.
Geographic good luck may have allowed Homo sapiens to move into Neandertals' former haunts.
Neandertals didn't get dumped on prehistory's ash heap -- it got dumped on them. At least three volcanic eruptions about 40,000 years ago devastated Neandertals' western Asian and European homelands, spurring a rapid demise of these humanlike hominids, says a team led by archaeologist Liubov Golovanova of the ANO Laboratory of Prehistory in St. Petersburg, Russia.
Modern humans survived because they lived in Africa and on the tip of southwestern Asia at that time, safely outside the range of volcanic ash clouds, Golovanova's group proposes in the October Current Anthropology. If that scenario pans out, then geographic good luck allowed Homo sapiens to move into Neandertals' former haunts after a couple thousand years without having to compete with them for food and other resources, as many researchers have assumed.
Advances in stone toolmaking and other cultural innovations achieved by modern humans shortly after 40,000 years ago supported survival in harsh, postvolcanic habitats, Golovanova and his colleagues hypothesize.
"For the first time, we have identified evidence that the disappearance of Neandertals in the Caucasus coincides with a volcanic eruption approximately 40,000 years ago," Golovanova says.
His new study focuses on soil, pollen, animal bones and stone tools from Mezmaiskaya Cave in southwestern Russia's Caucasus Mountains. Excavation of this cave began in 1987.
In a comment published along with the new study, archaeologist Paul Pettitt of the University of Sheffield in England agrees that Neandertals disappeared at Mezmaiskaya Cave and its surrounding region shortly after volcanic eruptions identified by Golovanova's team. But the timing of Neandertal and modern human occupations over at least 10,000 years in an area covering tens of thousands of square kilometers in Europe and Asia remains poorly understood, Pettitt cautions.
Chemical analyses of soil layers in the Russian cave identified two types of volcanic ash denoting separate volcanic eruptions in western Asia between 45,000 and 40,000 years ago. Plant pollen recovered in the cave indicates that extremely cold, dry conditions prevailed around the time these ash layers formed.
Other researchers, led by anthropologist Francesco Fedele of the University of Naples in Italy, have recently reported evidence of an unusually large volcanic eruption in Italy around 40,000 years ago. That event created a "volcanic winter" that devastated the ecology of southern and eastern Europe, in their view.
These three volcanic eruptions and perhaps others wreaked havoc on Neandertals' habitats and devastated their already small populations, Golovanova's group hypothesizes.
Signs of Neandertal activity at Mezmaiskaya Cave declined sharply after the first western Asian volcanic eruption and disappeared after the second blast, the researchers say. By 40,000 years ago, cave sediment contains no bones of hunted animals or Neandertal-made stone tools.
Thin, double-edged stones, perforated shells for stringing on necklaces, bone points and other items characteristic of Stone Age H. sapiens turn up between 38,000 and 37,000 years ago in Mezmaiskaya Cave, they add.
That's consistent with indications from the Neandertal genome (SN: 6/5/10, p. 5) that interbreeding with modern humans was relegated to the Middle East, where the two species lived in close proximity before H. sapiens spread to Europe and Asia, Golovanova says.
In another comment published with the new paper, geologist Biagio Giaccio of the Institute of Environmental Geology and Geoengineering in Rome challenges Golovanova's account. Excavations in four southern Mediterranean caves have unearthed modern human tools that, contrary to the new proposal, are slightly older than ash layers from the 40,000-year-old volcanic eruption in Italy, Giaccio notes.
Further work is needed to confirm that Neandertals abandoned Mezmaiskaya Cave before modern humans showed up in the region, he says.