Elephant-Sized Apes That Once Roamed the Land Mysteriously Vanished. Now, Scientists Have an Answer.

Some 330,000 years ago, giant apes the size of elephants roamed the forests of southern China. Their massive teeth—once sold as a "dragon tooth" by a Hong Kong apothecary—gnawed tough leaves and devoured fruit. Then suddenly, while other primates were thriving, these supersized orangutan-like creatures vanished with almost no trace.

Now, a new study published in Nature has solved the long-standing mystery of the apes’ demise. Researchers have discovered that the primates (Gigantopithecus blacki) went extinct between 295,000 and 215,000 years ago because they were unable to adapt their eating habits and behavior to a rapidly-changing climate. 

“The story of G. blacki is an enigma in paleontology,” said co-lead author Yingqi Zhang, from the Institute of Vertebrate Palaeontology and Palaeoanthropology at the Chinese Academy of Sciences, in a press statement. “How could such a mighty creature go extinct at a time when other primates were adapting and surviving?”

Gigantopithecus is the only great ape to go extinct in the earth’s most recent period, the Pleistocene. All other groups of great apes, including gorillas, chimpanzees, orangutans and human ancestors are still around today.

Up until now, part of the mystery stemmed from just how few G. blacki fossils there are—after more than 85 years of searching, archaeologists have only found teeth and four jaw bones—and how little the species’ final resting place had been studied. The breakthroughs came when researchers collected a wealth of evidence including fossils, quartz, sediment, and pollen from 22 cave sites across the Guangxi Province in southern China, and dated these using six different techniques.

Reconstructing an extinction event like this is a rare feat in paleontology and took precise dating, says geochronologist and study co-author Kira Westaway. “With extinctions it’s all about timing. If you don’t have great timing, then you’re just looking for clues in the wrong places or you’re just looking at really long time periods,” the Macquarie University associate professor told Motherboard.

To date each site, researchers used dating techniques like measuring how much uranium the fossils had soaked up over time, or analyzing the light signal that quartz in the soil gave off when they’re blasted with a laser. This gave them more than 150 ages, which fell in the narrow window between 295,000 and 215,000 years.

“We wanted to be really accurate so we could look at what the environment was doing at that time,” said Westaway. Unfortunately, the environmental records that were already available weren’t very detailed, so the researchers also reconstructed the environment the giant apes lived in using pollen, super-detailed sediment analysis, and analyses of isotopes found in G. blacki’s teeth. 

Roughly 2.3 million years ago, their habitat was a vibrant forest with a mosaic of trees and grasses. “We see both orangutans and Giganto really thriving in this forested environment,” said Westaway.

But the landscape radically changed just before the giant apes went extinct, between 600-300,000 years ago. What was once abundant forest cover became patchy, open plains dotted with ferns and grasses. And what was once a comfortable climate with their preferred food and water available year-round, was now unstable, with water limited to the wet season. 

This unstable environment put G. blacki under immense stress. While their orangutan cousins were small and limber enough to travel further to seek other food sources, the massive, encumbered G. blacki stayed put and stuck to their former diet. As their favorite fruits dwindled, the apes were forced to switch to less nutritious fare—probably barks, sticks or whatever they could find on the ground, said Westaway. This tough diet meant individuals were probably malnourished and dehydrated in the years leading up to their species’ extinction. 

These declining numbers and chronic physical stress show up in banded marks on the fossilized teeth the researchers studied. Eventually, the environment became too open—and food sources became too scarce—for the giant apes to survive. 

This drastic environmental change echoes what’s currently happening in ape habitats around the world as a result of deforestation and climate change. “We’ve got the potential for this sixth mass extinction event like we’ve seen in the past in our geological records. It’s really crucial to understand how species respond to environmental stressors,” said Westaway. “I’m passionate about going back and looking at these unresolved extinctions and working out what we can learn from them.” 

The next big goal for Westaway, Zhang and their team is finding the ever-elusive postcranial remains, or fossils from other parts of G. blacki’s body other than the head. Since completing this latest study, Zhang’s team has already uncovered six new cave sites, which they hope will unearth these never-before-seen remains.