AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS)—As early Homo sapiens spread across Eurasia about 45,000 years ago, they may have experienced much colder climate conditions than previously thought, according to isotope analyses of animal remains from a Bulgarian cave, which also contains some of Europe’s earliest H. sapiens remains. The findings* contradict models that suggest warm climates were necessary for human expansion in the region, providing direct evidence that at least some dispersals occurred when air temperatures in the cave were 10°Celsius to 15°C lower than temperatures today. Current models based on age correlations between archaeological and climatic records propose that H. sapiens spread across Eurasia only during episodes of warm climate. However, these studies tend not to use direct paleoclimate evidence, instead generating models that correlate the ages of archaeological finds with climatic phases documented in ice cores or cave deposits. To provide direct evidence for the climate conditions during the time when H. sapiens first spread across Eurasia, replacing Neanderthals within a few millennia, Sarah Pederzani and colleagues analyzed strontium and oxygen isotopes from the tooth enamel in remains of equids and bison from the Initial Upper Paleolithic (IUP) in Bulgaria’s Bacho Kiro Cave. They used a sequential method to sample the enamel layer-by-layer, enabling them to see changes in the isotopes over short intervals of time, as the tooth enamel was deposited during the animal’s development. The strontium isotopes were stable, which showed that the animals did not migrate over long distances, confirming the suitability of the remains to help reconstruct the local climate. However, the oxygen isotopes did fluctuate, enabling the researchers to estimate changes in seasonal temperature as well as annual mean temperatures. Pederzani et al. determined that the oxygen isotope levels were much lower than those expected for the modern-day Balkans climate, aligning better with current, colder conditions in Scandinavia and Russia.
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Article Source: AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS) news release.
Summary author: Shannon Kelleher
*Subarctic climate for the earliest Homo sapiens in Europe, Science Advances, 22-Sep-2021. 10.1126/sciadv.abi4642
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