An international team of researchers found out a registered mass extinction that affected the megafauna in South America might have been caused by a combination of climate change and increased human activity in the area.
They got to this conclusion after studying the fossil registers from South America, mainly a zone between Modern Argentina and Chile called Patagonia. The area includes the south part of the Andes and has two coasts to the Pacific and the Atlantic Ocean. Scientists have reported that the fossils in this area are exceptionally well preserved, and thousands of years ago, it was the home of megafauna’s species.
The term megafauna comes from Latin, and it means large animals. Other than this, its definition is not well established as some say that every animal that weighs more than 40 pounds enters this category including Humans. However, most of the time when specialists use this term, they refer to animals way bigger than humans, such as elephants giraffes, cows and so on. As a curious fact, reptiles are not sorted by this criterion, only mammals.
There are verified registers that place a mass extinction that affected these abundant species around 12,000 years ago in Patagonia. 3,000 years before that, human beings arrived the area amidst a cold area where big furred mammals like sabretooth cats and giant bears were at the top of the food chain.
Humans managed to establish and live in harmony with their massive neighbors, but that suddenly changed. In a period of just 300 years, the species forming the megafauna started to disappear from the registers, and scientists are digging up the story of what happened in the late Pleistocene.
The research team realized there is more than just human activity to it
Until now, scientists had accepted the Blitzkrieg theory to explain this mass extinction. According to it, human communities got quite large after they established in the area. An area fit for the need for food, shelter and security became greater for the human population. To satisfy their necessities, human’s ancestors developed sophisticated hunting methods to deal with the biggest animals.
They realized that even though it was incredibly dangerous, the amount of food a single giant mammal provides is worth the risk. Moreover, they could use the skin to protect themselves from the cold, and their bones to eventually make tools. However, a lot of specialists say that this is very unlikely because of the period.
“To characterize the extinction of the Late Pleistocene Patagonian megafauna, we sequenced mitochondrial DNA from 89 megafaunal bone and teeth samples recovered from caves and rock shelters, and generated new accelerator mass spectrometry radiocarbon dates for a total of 71 bone, teeth, and coprolite samples. We then investigated whether the megafaunal extinctions were associated with major events in records of climate change and/or human occupation,” reads the report titled “Synergistic roles of climate warming and human occupation in Patagonian megafaunal extinctions during the Last Deglaciation.”
The researchers investigated deaths occurred thousands of years ago
Jessica L. Metcalf, who works at the Australian Center for Ancient DNA-based at the University of Adelaide, South Australia, is the leader of a group of researchers that includes specialists from the University of Colorado, the University of Oxford, and the Natural Museum of History in Denmark, and so on.
The team analyzed the remains dig up from sites located in the Patagonia and identified them to be from the late Pleistocene. They said that many unknown factors preceded the event. In fact, they spotted a couple of species scientists were not aware of such as an ancestor to the modern Puma.
Furthermore, they overlapped the period in which the massive deaths took place and the period when human beings arrived the area, and then, compared it to the weather records from the area during that period. They realized that human presence had not greatly affected other populations until the temperature started to rise near the end of the Pleistocene. They said there wasn’t enough information to infer that the growth of human population in numbers was a factor, but they identified that in other areas of the world, severe extinctions were registered when the climate changed.
“Human presence, in combination with the rapid advance of forests and environmental changes associated with the ensuing warming phase, appears to have led to the collapse of the megafaunal ecosystem within a few hundred years” reads the paper.
The study was published on-line by Science Advances on June 17, 2016.
Source: Science Advances