Illustration of the Deinotherium genus, an animal that became extinct after the evolution of humans
Heinrich Harder/Florilegius/Alamy
An AI-powered analysis of thousands of fossils suggests that human hunting was the main factor behind the extinction of dozens of elephant-like species over the past two million years.
The study found that the extinction rate of these animals increased five-fold when early humans evolved about 1.8 million years ago, and then increased again when modern humans emerged. Today, only three species of elephants from this group remain.
“If early humans had never appeared, the number of species would probably still be increasing,” says Torsten Hauffe of the University of Fribourg in Switzerland.
Hauffe said the number of species of elephant-like animals known as proboscideans, from the Latin word for “nose,” increased millions of years before humans arrived, probably due to the evolution of stronger teeth for eating grass.
By 1.8 million years ago, there were about 30 species of organisms living in Africa whose ranges were beginning to overlap with those of early humans. Deinotherium bozaciIt had downward-pointing, backward-facing fangs growing from its lower jaw. D. Bozaci It became extinct about 1 million years ago.
By the time modern humans began to spread across the world about 130,000 years ago, only 15 species of proboscideans remained. Most of these species had gone extinct, leaving only the Asian elephant, the African bush elephant, and the African forest elephant.
To find out why, Hauffe and his colleagues developed a statistical model that uses fossil finds to estimate how rates of extinction and speciation have changed over time, and the possible reasons for these changes.
Previous models of this kind have been limited to looking at only the impact of one factor, such as climate, but by using AI, the team’s model can estimate the relative contributions of many factors, Hauffe says. “We put it all together in one analysis.”
The study concluded that overlap with humans was the most important factor contributing to extinction, followed by geographical distribution and tooth and tusk shape. For example, species restricted to islands, such as the dwarf Sicilian elephant, Palaeoloxodon falconeri, They were much more likely to become extinct.
Climate change, which some believe is the primary cause of extinction, came in fourth after these other factors, so the findings support the overhunting hypothesis, which suggests that human hunting was the primary culprit, Hauffe said.
A computer-modeling study of woolly rhinos earlier this year supported the idea that even low-level hunting can drive slow-breeding animals to extinction, says Steven Chang of the University of Helsinki in Finland, who was not involved in the proboscidean study but helped compile some of the fossil data that was analyzed.
But after a team including Zhang analyzed the data in 2021, they concluded that while there may have been an early human influence, the underlying cause was climate.
What’s clear is that early humans didn’t suddenly wipe out proboscideans, Zhang says: “In fact, some of the most fascinating extinct elephant species emerged during this period, including giant elephants.” Palaeoloxodon These include the giant mammoths of Eurasia, which stood 4 metres at the shoulder and weighed 25 tons, and the familiar woolly mammoths.
Where early humans slaughtered mammoths Palaeoloxodon The species dates back more than a million years, says Chang, “and both lineages have survived for the past 25,000 years alongside prehistoric humans with much more advanced cognitive and technological capabilities.”
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