The Campanian Ignimbrite (CI)
eruption in Italy 40,000 years ago was one of the largest volcanic cataclysms
in Europe and injected a significant amount of sulfur-dioxide (SO2) into the
stratosphere. Scientists have long debated whether this eruption contributed to
the final extinction of the Neanderthals. This new study by Benjamin A. Black
and colleagues tests this hypothesis with a sophisticated climate model.
Black and colleagues write that the
CI eruption approximately coincided with the final decline of Neanderthals as
well as with dramatic territorial and cultural advances among anatomically
modern humans. Because of this, the roles of climate, hominin competition, and
volcanic sulfur cooling and acid deposition have been vigorously debated as
causes of Neanderthal extinction.
They point out, however, that the
decline of Neanderthals in Europe began well before the CI eruption:
"Radiocarbon dating has shown that at the time of the CI eruption,
anatomically modern humans had already arrived in Europe, and the range of
Neanderthals had steadily diminished. Work at five sites in the Mediterranean
indicates that anatomically modern humans were established in these locations
by then as well."
"While the precise implications
of the CI eruption for cultures and livelihoods are best understood in the
context of archaeological data sets," write Black and colleagues, the
results of their study quantitatively describe the magnitude and distribution
of the volcanic cooling and acid deposition that ancient hominin communities
experienced coincident with the final decline of the Neanderthals.
In their climate simulations, Black
and colleagues found that the largest temperature decreases after the eruption
occurred in Eastern Europe and Asia and sidestepped the areas where the final
Neanderthal populations were living (Western Europe). Therefore, the authors
conclude that the eruption was probably insufficient to trigger Neanderthal
extinction.
However, the abrupt cold spell that followed the eruption
would still have significantly impacted day-to-day life for Neanderthals and
early humans in Europe. Black and colleagues point out that temperatures in
Western Europe would have decreased by an average of 2 to 4 degrees Celsius
during the year following the eruption. These unusual conditions, they write,
may have directly influenced survival and day-to-day life for Neanderthals and
anatomically modern humans alike, and emphasize the resilience of anatomically
modern humans in the face of abrupt and adverse changes in the environment.
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