Anonim

A new research based on the dating of a large number of finds, more precise dating and new methods of statistical analysis of the results rekindles the infinite debate on the responsabilities of the extinction of large mammals such as mammoths, saber-toothed tigers, giant wolves and other. The two main positions are not very distant from each other, but they propose two readings of the history reversed one with respect to the other. The first attributes the responsibility to man, with the contribution of climate change (we talked about it in Who killed the great animals of the past ?, in 2014); the second blames climate change, but with the contribution of man: this interpretation is today reinforced by the study we present here.

During the Pleistocene, to decree the extinction of the woolly pachyderms and other species of the so-called megafauna (heavy mammals more than 40-45 kilos) was a rapid increase in the global temperature of the Earth, a global warming that has changed the ecosystem of the planet.

According to a study published in Science, which however does not completely absolve Homo sapiens from its responsibilities.

Continuous replacement. Over the last 450 million years, the Earth has seen a succession of 5 mass extinctions (perhaps 6), caused by dramatic events such as the fall of an asteroid. Although on a smaller scale compared to these critical phenomena, in geologically more recent times there has been another significant biotic transition, which at the turn of the last glaciation (about ten thousand years ago) saw the disappearance of mammoths, tigers from teeth to saber, woolly rhinos and giant sloths.

One of the most accredited theories, supported also by recent research, claims that the end of the massive mammals in Europe, Asia and North America was the Homo sapien s, which with its innovative hunting techniques established itself as a new super predator, by exterminating mammoths and other herbivore species directly or by removing food from the mouth of large carnivores.

The heat you don't expect. The new study, to which Australian and US scientists have collaborated, shows that behind these extinctions there would actually be rapid climatic fluctuations, known as Dansgaard-Oeschge events.

As Alan Cooper, coordinator of the study and director of the Australian Center for Ancient DNA, explains, during the last Ice Age there were sudden temperature rises that turned vegetation and rainfall distribution upside down, causing the inexorable decline of many animal species .

Method. Combining advanced DNA analysis and radiometric dating systems, the researchers examined fossils from various museums, then compared the data obtained with information on climate change in the northern hemisphere in the late Pleistocene - Dansgaard-Oeschger events can be dated accurately by core drilling of the Greenland ice sheet.

The comparison, made possible thanks to an innovative statistical method, has thus made it possible to find a correlation between the prehistoric heat waves and the decimation of the megafauna.

Man's hand. Chris Turney, who contributed to the drafting of the report, says that despite research points to climate change, it must be recognized that Homo Sapiens also played a role in the disappearance of mammals such as the mammoth.

"The sudden warming has caused enormous changes for the environment, " concludes the professor of the University of New South Wales (Australia), "but the rise of human beings has inflicted the coup de grace on a population that was already under stress" .