New study blames humans for megafauna extinction
A new study published in the journal Quaternary International has added fuel to the long-running debate about how megafauna, such as woolly mammoths, giant sloths, and mastodons, became extinct, an article in Live Science reports. Various theories have attributed the extinctions to human hunting, climate change, disease, impacts from asteroids, or other causes. However, the latest research places the blame firmly on the shoulders of the humans.
A well-known mass extinction of megafauna, the Holocene extinction, occurred at the end of the last ice age glacial period and wiped out many giant ice age animals, such as woolly mammoths, in the Americas and northern Eurasia. However, this extinction pulse near the end of the Pleistocene was just one of a series of megafaunal extinction pulses that have occurred during the last 50,000 years over much of the Earth's surface, with Africa and southern Asia being largely spared.
Australian megafauna. Image source.
According to the new study, the loss of species correlates more closely with the arrival of humans than with changes in climate with megafaunal extinctions following a distinctive landmass-by-landmass pattern that closely parallels the spread of humans into previously uninhabited regions of the world.
"The evidence really strongly suggests that people were the defining factor," said study leader Chris Sandom, co-founder of the consulting firm Wild Business Ltd., who completed the work as a postdoctoral researcher at Aarhus University in Denmark.
Sandom and his team gathered records on individual species known to have gone extinct between 132,000 years ago (at the beginning of the last interglacial period) and 1,000 years ago. They focused their analysis not on the continent level, as many studies have, but country-by-country or even state-by-state, in large nations like the United States. All told, the researchers analyzed 177 extinct mammals.
They found that the lowest numbers of extinctions occurred in sub-Saharan Africa, followed by Eurasia. The most extinctions occurred in Australia and the Americas, where humans are believed by most scholars to have arrived later. Overall, the results demonstrated that humans' arrival was responsible for 64 percent of the variation in extinction rates around the globe, while temperature changes explained 20 percent of the variation, mostly in Eurasia.
Sandom explained that climate change can stress animals, but do not always spell doom for species — animals may simply alter or restrict their range in order to find a habitat that sustains them. Humanity may have disrupted this adaptive process for large mammals, he said. "That was the final straw," Sandom said. "They couldn't handle the new predator turning up."
Featured image: Ancient humans hunting a large mammal. Image source.