What are stalagmites?
Stalagmites grow in thin layers each year and any change in temperature alters their chemical composition. The layers therefore preserve a natural archive of climate change over many thousands of years.
The researchers examined stalagmites in two Romanian caves, which revealed more detailed records of climate change in continental Europe than had previously been available.
From looking closely at the layers of the stalagmites, the archaeologists were able to identify a series of prolonged cold and dry periods in Europe between 44,000 and 40,000 years ago. Temperatures would gradually cool, staying very cold for centuries or even millennia, and then warm up again very abruptly.
Neanderthal presence declined during cold periods
These cold periods coincide with the timings of a near complete absence of archaeological artefacts from the Neanderthals. From this, it has been suggested that changes in climate had a significant impact on the long-term survival of Neanderthal man.
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A model an adult Neanderthal male head and shoulders on display in the Hall of Human Origins in the Smithsonian Museum of Natural History in Washington, D.C. Credit: Tim Evanson[/caption]
Dr Vasile Ersek is co-author of the study and a senior lecturer in physical geography in Northumbria University’s Department of Geography and Environmental Sciences. He explains: “The Neanderthals were the human species closest to ours and lived in Eurasia for some 350,000 years. However, around 40,000 years ago – during the last Ice Age and shortly after the arrival of anatomically modern humans in Europe – they became extinct.
“For many years we have wondered what could have caused their demise. Were they pushed ‘over the edge’ by the arrival of modern humans, or were other factors involved? Our study suggests that climate change may have had an important role in the Neanderthal extinction.”
Why did modern humans survive cold periods?
The researchers have stated that modern humans survived these cold conditions – known as stadial periods – because they were more adaptable to their environment.
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Credit: Le Moustier Neanderthals by Charles R Knight, 1920[/caption]
While Neanderthals were skilled hunters and were able to use fire, their diet wasn’t as diverse as that of modern humans. They lived mainly on meat, so when that food source became more scarce during colder periods, Neanderthals became vulnerable.
By this time, modern humans had begun to incorporate fish and plants into their diet – potentially marking them for survival.
According to Dr Ersek, the research team’s findings have indicated that this cycle of “hostile climate intervals” over thousands of years, in which the climate varied abruptly and was characterised by extreme cold temperatures, was responsible for the future European demographic.
“Before now, we did not have climate records from the region where Neanderthals lived which had the necessary age accuracy and resolution to establish a link between when Neanderthals died out and the timing of these extreme cold periods,” he said, “But our findings indicate that the Neanderthal populations successively decreased during the repeated cold stadials.
“When temperatures warmed again, their smaller populations could not expand as their habitat was also being occupied by modern humans and this facilitated a staggered expansion of modern humans into Europe.
“The comparable timing of stadials and population changes seen in the archaeologic and genetic record suggests that millennial-scale hostile climate intervals may have been the pacesetter of multiple depopulation-repopulation cycles. These cycles ultimately drew the demographic map of Europe’s Middle-Upper Paleolithic transition.”
Read more about the difference between Neanderthals and modern humans here.