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Grough ground sloths, musk oxen and short-faced kangaroos: All have gone the way of the dodo, vanished from the face of the earth. This is just a sampling of the large mammals that are no longer with us. Of the 57 species of megaherbivores known to have existed 50,000 years ago, only 11 survive. That’s a dismal 81 percent extinction rate.
Defined as large-bodied land mammals with an average body mass of 2,200 pounds or more, the remaining megaherbivores today include elephants, rhinoceroses, giraffes, and hippos. These animals play critical roles in their ecosystems, from seed dispersal to landscape management.
Elephants, for example, reduce the density of trees and shrubs through their movement and feeding habits. These open spaces make way for range animals such as antelope and zebra, while hollows and crevices formed by broken branches and felled trees create habitats for small mammals, insects and fungi.
But these huge creatures—which can’t hide under a log or move as nimbly as gazelles—were especially vulnerable to early humans looking to get the most out of every hunt. After all, if you’re looking for meat to fill your belly and fur to keep your family warm, a woolly mammoth has a lot more to offer than a rabbit.
“We know that prehistoric humans were very focused on hunting large species,” says Jens-Christian Svenning, director of the Danish National Research Foundation’s Center for Ecological Dynamics in the New Biosphere at Aarhus University. He is also the lead author on a recent paper published in Cambridge Prisms: Extinction This argues that it was not climate change but human hunting that caused the extinction of most megaherbivores over the past 50,000 years.
A woolly mammoth has much more to offer than a rabbit.
To draw their conclusions, Svenning and his team analyzed ancient extinction, climate and human migration data collected over the past six decades. The work continues a conversation that began in earnest in 1966 when an American palaeontologist named Paul Schultz Martin first put forward his over-the-top hypothesis—where he suggested that migrating humans hunted North America’s megafauna from the Pleistocene epoch to extinction. . A few years ago, researchers published a paper in Nature who also found that megafauna distributions in time and space in prehistoric South America closely match human demographic records, as well as findings of spear points called fishtails in the archaeological record.
“It’s a long-term discussion,” says Svenning, who argues that improvements in research techniques and data quality over the past few decades have helped bring us closer to a definitive answer about how things went for the megafauna. “We have a much better understanding now than we did in the 1960s,” he says. “What we’ve done is reassessed all of this data, and that allows us to say that overall, we can really rule out that climate played a big role in this kind of extinction.”
The where and when of the extinctions simply don’t match global patterns of climate change, according to the data the researchers collected and analyzed, but they do correspond closely with patterns of human colonization — occurring at or after our arrival at many different times and places around the world. the globe.
“We conclude that it is one of the strongest and most stable models we have in ecology,” says Svenning. His team’s findings show that these megafauna extinction patterns began when humans first migrated out of Africa about 100,000 years ago. Extinctions accelerated approximately 50,000 years ago as Eurasia and Australia were colonized by large game hunters.
Finishing at the business end of a spear had such a significant impact on large mammals because they have a naturally slow replacement rate. Gestation periods are long, and so is the maturation process. The 46 species of megaherbivores lost to history simply could not have reproduced fast enough to compensate for human killing.
Felisa Smith, a conservation paleoecologist and professor at the University of New Mexico, believes that human influence in the extinction of megafauna is no longer up for debate. “I think the work over the last few decades has shown pretty convincingly that humans had a pretty significant part in the extinction,” says Smith.
This is not about assigning blame, says Svenning. “People who lived thousands of years ago never had access to the full picture. These things happened over long time scales and vast spatial scales over which no one had an overview; whatever people did, it was hard to see the consequences. Plus, of course, people just had to survive as best they could.”
Svenning hopes readers will take away a greater understanding of the relationships between humans and megafauna and the natural world. Large mammals remain highly vulnerable to extinction today, with over half of extant species weighing over 22 pounds listed as vulnerable, endangered or critically endangered by the International Union for Conservation of Nature. “When we restore forests, we can’t just think about the trees,” he says. “We have to think about the animals that belong there.” 
Main image: maradon 333 / Shutterstock
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