Scientists have long debated why woolly mammoths, giant sloths and 44 other giant, plant-eating “megaherbivores” became extinct about 50,000 years ago.
Some paleontologists, biologists and others have argued that drastic climate changes during the past two ice ages were responsible for the extinction of these majestic creatures. But a new study has found another culprit: humans.
A comprehensive study that synthesized paleoclimatic data, preserved DNA samples, archaeological evidence and more has found that “human predation” by early hunter-gatherers is now the explanation most supported by all available evidence.
“There is strong, cumulative evidence for direct and indirect pressures from behaviorally modern humans,” the team concluded in their new study.
According to researchers, humans were ‘the main driver’ of the extinction of these species.
Scientists have long debated why woolly mammoths, giant sloths, and another 44 giant, plant-eating “megaherbivores” became extinct about 50,000 years ago. Above, an engraving by Ernest Grise of a prehistoric man hunting a woolly mammoth
Scientists call large animals, defined as anything weighing more than 45 kilograms (100 pounds), “megafauna,” and their above-average extinction rates in modern times have caused both concern and fascination.
“The large and highly selective loss of megafauna over the past 50,000 years is unique in the past 66 million years,” said the study’s lead author Jens-Christian Svenningwho conducts research on paleoecology and biodiversity at Aarhus University.
“Previous periods of climate change did not lead to large, selective extinctions,” Svenning noted in a statement, “which argues against a major role for climate in megafauna extinctions.”
Svenning, who directs the Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) at the Danish National Research Institute at Aarhus University, led a team of seven other researchers who helped compile the new study.
An intriguing array of artifacts and physical evidence from the archaeological record helped support their conclusions, which were published in March in the journal Cambridge Prisms: Extinction.
Ancient traps designed by prehistoric people to capture very large animals, and analyses of human bones and protein residues on spear points found, all suggest that our ancestors skillfully hunted and ate some of the largest mammals in existence.
“Another striking pattern arguing against a role for climate is that recent megafauna extinctions hit climatically stable areas as hard as they did unstable areas,” Svenning said.
While a region’s vulnerability to climate change didn’t play a role in these extinctions, the influx of human hunters did, Svenning’s team found.
The researchers noted that 40 of the 48 known large mammals became extinct during this period (top right of graph), while only increasingly smaller percentages of the lower “weight class” of species became extinct. The bottom row breaks down these extinction rates by continent
The fossil record shows that these large species became extinct at very different times and at very different rates. Some species declined quite rapidly, others more gradually—in some cases over a period of 10,000 years or more.
Only a few of these extinctions match the climate data from this period, the so-called Late Quaternary. This period includes the end of the Pleistocene, the last two ice ages and the beginning of the Holocene, 11,700 years ago.
Many of these extinctions were associated with the local arrival of modern humans.
“Early modern humans were effective hunters of even the largest animal species, and clearly had the ability to reduce populations of large animals,” Svenning noted.
“These large animals were and are particularly vulnerable to overexploitation because they have long gestations, produce few offspring at a time and take many years to reach sexual maturity,” he added.
His team’s research into the extinctions of large animal species during this period found that 40 of the 48 largest animals, those weighing more than 1,000 kg, had become extinct.
From then on, extinction rates showed a downward trend by weight class, suggesting that megafauna and docile herbivores were particularly targeted.
Over the past millennia, from about 5,000 years to the present, the remaining megafauna are among the species most threatened by extinction due to human activities, including poaching and habitat loss.
The researchers specifically mentioned the global extinctions of the water buffalo species Bubalus mephistophelesa species of horse or horse-like animal called Equus ovodovi and the gibbon primate species Junzi imperialis.
They also raised the alarm about the declining numbers of several megafauna in China, the elephant species Big elephanttwo species of rhinoceros Dicerorhinus sumatrensis And Rhinoceros sondaicus And Panthera tigris tigers.
According to Svenning, the extinction of megafauna could undermine entire ecosystems, because the large animals play a role in seed dispersal, shape vegetation through their feeding habits and contribute to the nutrient cycle through their waste.
“Our results highlight the need for active conservation and restoration efforts,” the researcher said.
“By reintroducing large mammals, we can restore the ecological balance and support the biodiversity that evolved in ecosystems rich in megafauna,” Svenning concluded.