Humans may be to blame for megafauna extinctions, new study suggests: Science alert

Once upon a time, our world was home to many giants.

Actually, it wasn’t that long ago. Once the dinosaurs had had their day, our planet was home to a whole new range of giant animals. Sloths It ranged from humans, to woolly mammoths, to giant wombats and kangaroos, to the magnificent giga-goose.

About 50,000 to 10,000 years ago, Almost 200 The world’s largest animal species are gone forever, leaving nothing but their enormous bones (and burrows). It is not clear what these amazing creatures ultimately claimed.

During the period when the megafauna disappeared, the world warmed and an ice age ended, suggesting one possible mechanism: climate change. Meanwhile, our own species were expanding into new lands, chasing the wealth of resources brought by the retreating ice. So debate rages about the roles of these two potential contributing factors.

Now a new study on the decline of giant herbivorous mammals – megaherbivores – points to humanity.

Fossils show that by 50,000 years ago, there were at least 57 species of megaherbivores. Today only 11 remain. They include notable behemoths such as hippos and giraffes, as well as several species of rhinoceros and elephant, many of which continue to decline.

Researchers say such a dramatic decline is not consistent with climate change being the sole cause.

„The large and highly selective loss of megafauna in the last 50,000 years is unique to the last 66 million years. Earlier periods of climate change did not lead to large, selective extinctions, arguing against a major role for climate in megafauna extinctions.” says macroecologist Jens-Christian Svenning Aarhus University in Denmark

„Another striking pattern arguing against a role for climate is that recent megafauna extinctions have been as severe in climate stable areas as in unstable ones.”

The new study includes a comprehensive review of the evidence available since the extinction of the dinosaurs 66 million years ago. These include locations and times of extinctions, habitat and food preferences, estimated population sizes, evidence of human predation, human population movements, and climate and vegetation data dating back millions of years.

We know that humans coexisted with megafauna, and we have evidence of some species Hunted to extinction. We know that our ancestors were efficient hunters of large animals.

„Early modern humans were efficient hunters of even the largest animal species and clearly had the ability to deplete large animal populations.” Svenning says.

„These large animals are highly exploited because they have long gestation periods, produce very few offspring at a time, and take years to reach sexual maturity.”

New research shows that these human hunters were effective enough to contribute significantly to many extinctions. Megaherbivores, the team found, died out in a variety of climatic conditions in which they were able to thrive effectively even during the transition. Most of them would have adapted well to a warming environment, the researchers found.

They died out at different times and at different rates—but all of those times were after humans arrived, or developed the means to hunt them down. In fact, exploitation of mammoths, mastodons, and giant sloths is fairly consistent wherever humans go.

The reason the mammoths hung on to Wrangel Island was because there were no humans after the terrestrial population disappeared.

It’s a sobering thought, especially as a 2019 study found that human exploitation has decimated megafauna that survive today. About 98 percent of endangered megafauna species are at risk of extinction because people won’t stop eating them.

„Our results highlight the need for proactive conservation and restoration efforts.” Svenning says. „Reintroducing large mammals can help restore ecological balance and support biodiversity, which evolved in megafauna-rich ecosystems.”

Little wonder the rest of the animal kingdom terrifies us.

Published in the thesis Cambridge Prism: Annihilation.