The pace at which humans have been hunting down large mammals into extinction since the early ages, the largest remaining mammal in 200 years would be the domestic cow, warn researchers.
“Species that went extinct tended to be two to three times bigger than mammals that survived, a trend that was evident globally,” the study stated. The findings were published in Science.
Elephant-dwarfing wooly mammoths, elephant-sized ground sloths and various saber-toothed cats highlighted the array of massive mammals roaming Earth between 2.6 million and 12,000 years ago.
Previous research suggested that this phenomenon, known as size-biased extinction, began in Australia around 35,000 years ago. But newly new discovered fossil and rock records estimate that the extinction began in Africa, at least 125,000 years ago.
“It wasn’t until human impacts started becoming a factor that large body sizes made mammals more vulnerable to extinction,” Kate Lyons, a co-author on the study, said in a press release.
Current records state that Homo sapiens emerged as a species around 200,000 years ago. “So this occurred not very long after the birth of us as a species. It just seems to be something that we do,” said Lyons.
The study notes that when extinction began in Africa, African mammals were already 50 percent smaller than those on other continents. As humans began to migrate out of Africa, more size-biased extinctions began in other regions of the world – in places that aligned with well-known human migration patterns.
Additionally, the study found that both large and small mammals were vulnerable to temperature shifts throughout this era – meaning climate change wasn’t a factor in the extinction of these colossal animals.
“From a life-history standpoint, it makes some sense. If you kill a rabbit, you’re going to feed your family for a night,” Felisa Smith, the study’s lead author, said. “If you can kill a large mammal, you’re going to feed your village.”
Mammals that survived during the span were generally far smaller than those that went extinct.
The magnitude and scale of the recent size-biased extinction surpassed any other recorded during the last 66 million years, according to the study.
“What we’re doing is potentially erasing 40 to 45 million years of mammal body-size evolution in a very short period of time,” Lyons said.
“Ecosystems are going to be very, very different in the future. The last time mammal communities looked like that and had a mean body size that small was after the extinction of the dinosaurs,” Lyons said.