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Neanderthal extinction in Western Mediterranean area not caused by climate change

Neanderthal Man did not disappear as a result of climate change, at least not the numerous groups that until about 42,000 years ago lived in the western Mediterranean area. This is the conclusion drawn by a research group led by scholars from the University of Bologna, who managed to obtain a detailed paleoclimatic reconstruction of the last ice age by analyzing a series of stalagmites taken from some caves in Puglia.

Neanderthal extinction in Western Mediterranean area not caused by climate change
Stalagmites are ecellent paleoclimatic and paleoenvironmental archives
[Credit: O. Lacarbonara]
The study, published in Nature Ecology & Evolution, focused on the Murge karst plateau in Puglia, where Neanderthals and Homo sapiens lived together for at least three thousand years, from about 45,000 to 42,000 years ago. A period during which data extracted from stalagmites do not show significant climate change.

"The Apulian area we are researching emerges as a 'climate niche' during the transition between Neanderthal and Modern Man," explains researcher Andrea Columbu, the first author of the study. "It is therefore unlikely that drastic changes in climate have led to the disappearance of Neanderthals in Apulia and, by extension, in similar Mediterranean climatic areas".

Among the various hypotheses put forward to explain the extinction of the Neanderthal Man, which occurred in Europe about 42,000 years ago, the climatic scenario has gained considerable consensus among scholars. According to this theory, the primary cause of the disappearance of Neanderthals would have been the drastic and rapid climate changes occurred during the last Ice Age, which within a few centuries led to colder and drier climates.

Evidence of these sharp changes in climate is indeed found in analyses of Greenland ice cores and other paleoclimatic archives from continental Europe. However, when considering some areas of the Mediterranean, within which Neanderthal Man has been present for 100,000 years, the available data do not support these conclusions. In particular, in the western Mediterranean area, an area rich in prehistoric finds, no detailed paleoclimatic reconstructions from the regions that were populated by the Neanderthals were available until now.

Neanderthal extinction in Western Mediterranean area not caused by climate change
Scholars at work in the cave of Pozzo Cucu, in the area of Castellana Grotte, in Apulia
[Credit: O. Lacarbonara]
In order to obtain information on the climatic past of the western Mediterranean, the research group of the University of Bologna turned its attention to the Apulian Murge plateau. "Puglia is of fundamental importance for the understanding of anthropological dynamics, because we know that it was inhabited by both Neanderthals and Homo sapiens from about 45,000 years ago," says Andrea Columbu. "It is one of the few areas in the world in which the two species have shared a relatively limited territory in size, and for this reason it is unique in the study of climatic and bio-cultural factors at the heart of the transition between Sapiens and Neanderthals".

So how can we reconstruct the climate of that area in such a remote time? The answer lies in the stalagmites, calcareous formations that emerge from the soil of the karst caves and are formed by the continuous fall of water drops rich in calcite. "The stalagmites are excellent paleoclimatic and paleoenvironmental archives," explains Jo De Waele, professor at the University of Bologna who coordinated the study.

"Their formation requires the infiltration of rainwater from outside and this makes them an indisputable evidence of the presence or absence of rain; moreover, the isotopes of carbon and oxygen of calcite of which they are composed give indications regarding the state of the soil and the amount of rain during the whole period of their formation. All this information can then be intertwined with radiometric datings that make it possible to reconstruct with precision the various phases of 'growth' of the stalagmites in the caves".

It was precisely the rhythm of development that was the first significant element highlighted by the study. The analysis by the researchers showed that the Apulian stalagmites were characterized by continuous deposition throughout the last glacial cycle, and also in previous glacial cycles. This means that during the millennia considered there has not been any drastic climatic variation: a significant decrease in rainfall would have caused a cessation in the formation of stalagmites.

Neanderthal extinction in Western Mediterranean area not caused by climate change
Sampling of a stalagmite that formed between about 106,000 and 27,000 years ago
[Credit: O. Lacarbonara]
Among those analyzed, one stalagmite in particular has provided important information. Sampled in the cave of Pozzo Cucu, in the area of Castellana Grotte, in the province of Bari, is a stalagmite about 50 centimetres long on which 27 very high resolution dates and about 2,700 analyses of stable isotopes of carbon and oxygen were carried out. Dating has determined that its period of formation is between about 106,000 and 27,000 years ago, thereby making this stalagmite the most chronologically extensive evidence of paleoclimate in the western Mediterranean and European area during the last glacial period. And also in this case no trace of drastic climatic variations that may be connected with the extinction of the Neanderthals has been found.

"Our analyses show slight variations in rainfall in the period between about 50,000 and 27,000 years ago, but not enough to generate a variation in the vegetation on the soils above the cave," says Jo De Waele. "Throughout this period, and therefore also during the 3,000 years of cohabitation between Sapiens and Neanderthals and during the disappearance of Neanderthals, the carbon isotopes indicate a constant bio-productivity of the soils, which indicates the absence of drastic changes in the vegetation, and therefore in the climate."

The data that emerged from the study seem to show that the great variations in climate during the last Ice Age were different in the Mediterranean area than in continental Europe and the high latitudes of Greenland. This would lead to the exclusion of the climatic hypothesis as the cause of the extinction of Neanderthals.

But how can the disappearance of this human species, after a few millennia of coexistence with Modern Man, be explained then? Stefano Benazzi, paleoanthropologist of the University of Bologna, is one of the authors of the study. "The results of this research further strengthen the hypothesis advanced by various scholars that there is a technological explanation for the extinction of the Neanderthals", explains Benazzi. "According to this theory the hunting technology, which was much more advanced for Homo sapiens than for Neanderthals, seems to have contributed in a primary way to the supremacy of the former compared to the latter, leading to the disappearance of Neanderthals after about 3,000 years of coexistence between the two species".

Source: Universita di Bologna [trsl. TANN; July 10, 2020]


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