The largest known primate ever to live, which may have stood some 10 feet tall and weighed between 440 and 660 pounds, lumbered through the lush forests of southeastern Asia for millennia. It has left scientists a few thousand teeth, four jawbones and one gigantic mystery: Why did this huge creature die out?
In a study published on January 10 in Nature, researchers offer a new explanation for what caused the extinction of Gigantopithecus blacki, or “Giganto,” as some scientists refer to the species. Over thousands of years, the study suggests, local wet and dry seasons intensified, and the plants that made up the giant primates’ forest home changed. That meant the animals could no longer find enough nutritious food to reliably power their huge body. They paid the price for being so slow to adapt: they disappeared, even as orangutans, smaller relatives that today weigh up to 200 pounds, thrived.
It’s a new angle on the current hypothesis for Giganto’s demise, which holds that G. blacki simply couldn’t survive as dense forest gave way to more open landscapes in a drying climate. Instead the researchers argue that the extinction happened earlier in the ecosystem shift, long before the trees thinned. “The forest cover is still pretty high when Giganto goes extinct, so it wasn’t just a deterioration of the forest. It was more Giganto’s response to this changing plant community,” says study co-author Kira Westaway, a geochronologist at Macquarie University in Australia.
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A reconstruction of G. blacki. Credit: Garcia/Joannes-Boyau/Southern Cross University
Westaway and her colleagues first attempted to pinpoint when G. blacki disappeared. The team employed a barrage of techniques—four for dating sediments and two for dating fossils—to study Giganto teeth from 11 Chinese caves. The results suggested the species went extinct sometime between 295,000 and 215,000 years ago, which gave the researchers a firm time line to work from. “If you don’t get accurate dating for the evidence, then you’re looking for clues in the wrong places,” Westaway says.
With this “extinction window” pinned down, she and her colleagues turned to piecing together an image of what the environment would have looked like shortly before and during the years when G. blacki disappeared. In particular, the researchers studied pollen particles found in the caves and classified whether these particles represented trees, shrubs or species, such as ferns, that often rush in after an ecosystem experiences a disruption. The scientists also analyzed the fossilized teeth directly by looking at microscopic wear patterns for signs of what Giganto was eating.
“During the period of extinction, we see a lot more scratches and pits on the teeth, showing that it was eating more fibrous foods like bark and twigs,” Westaway says. She and her colleagues argue that this suggests Giganto lost access to softer, more nutritious fruit early in the climate transition. While orangutans were able to harvest from the upper canopy and make longer foraging trips, their massive cousins were too large to swing through the trees and were instead stuck scrounging whatever they could on the ground—and it cost the species its survival. “Giganto was slow to adapt, unable to adapt, just kept sticking to the same routine, and it just wasn’t working for him at all,” Westaway says.
Sherry Nelson, an anthropologist at the University of New Mexico, who has studied G. blacki but was not involved in the new research, says she’d like to see more data and deeper analyses before rewriting the story of the species’ extinction. She says this story still boils down to G. blacki losing the environment it needed to survive. “It hasn’t changed from what I thought before,” she adds. “This is a forest animal. We know during this period, we’re losing forest, and you’re going to lose the apes associated with it.”
Both Nelson and Westaway note that while G. blacki is striking for its mysterious extinction, equally striking is the orangutan’s persistence through the changing conditions. “There is a cost to being really big,” Nelson says—and the largest primate ever to live paid it in full. Understanding what triggered the animal’s extinction may help scientists prevent its smaller cousins from following the same path amid the upheaval caused by humans.
“Giganto is a really good starting point for understanding why certain species are vulnerable and why certain species are more resilient,” Westaway says. “We desperately need to understand what drives primate extinction.”