Mystery of Largest-Ever Primate's Disappearance Finally Solved

The mysterious demise of a giant ape—thought to be the largest primate ever to walk the Earth—has been unraveled by scientists.

A study published in the journal Nature has revealed how the extinct ape, known as Gigantopithecus blacki, disappeared due to its inability to adapt to a changing environment.

G. blacki was found in what is now southern China around two million years ago until the species went extinct before the arrival of humans in the region. The ape grew to an estimated height of about 10 feet and may have weighed roughly 440 to 600 pounds.

These creatures, which are very distant ancestors of humans, belong to the group of great apes known as Ponginae, whose only living members are the orangutans. Researchers speculate that G. blacki would likely have resembled an orangutan—albeit significantly larger—although this will only be confirmed once more fossils are found.

To date, the evidence of this species is restricted to four jawbones and around 2,000 fossilized teeth found in several cave sites dotted across two main areas of southern China. No fossils from the neck down have been found, leaving a significant gap in our knowledge of this animal.

The cave sites contain crucial evidence relating to the survival and eventual demise of the giant ape. But very few of these G. blacki sites have been dated using more than one radioactive dating technique, meaning the timing of the extinction has remained uncertain.

"Previously, it was assumed that G. blacki went extinct around 420-320,000 years ago based on the dating of only a few caves," Kira Westaway, co-lead author of the study with the Faculty of Science and Engineering at Macquarie University in Australia, told Newsweek.

In addition, the reasons why G. blacki disappeared have long been a mystery—particularly considering that it was one of the few Asian great apes to go extinct in the last two-and-a-half million years.

"The story of G. blacki is an enigma in paleontology—how could such a mighty creature go extinct at a time when other primates were adapting and surviving? The unresolved cause of its disappearance has become the Holy Grail in this discipline," Yingqi Zhang, co-lead author of the study from the Institute of Vertebrate Palaeontology and Palaeoanthropology at the Chinese Academy of Sciences (IVPP), said in a press release.

"The IVPP has been excavating for G. blacki evidence in this region for over 10 years but without solid dating and a consistent environmental analysis, the cause of its extinction had eluded us."

Zhang knew that a significant component of this mystery was the timing, so he decided to involve Westaway, a geochronologist.

"I am able to date the burial sediments that surround the G. blacki fossils. We have been working together since 2015 trying to solve the mystery of its demise," Westaway told Newsweek.

In the latest study, the scientists and their colleagues applied a multidisciplinary analysis to 22 caves in Guangxi Province, southern China. First, the team used dating techniques to establish a "window of extinction" during which the great ape disappeared between around 295,000 and 215,000 years ago.

"We have a much more robust timeline for their life and when they went extinct—rather than being based on evidence from one or two caves, we have sampled 22 caves over a wide area and employed six dating techniques to make sure that the timeline is accurate," Westaway said.

This window provided the researchers with a reliable time period to investigate the contemporary environmental conditions and how G. blacki was behaving and responding to its changing world.

The researchers reconstructed detailed environmental conditions during the extinction window using an analysis of pollen, fossils, sediments and stable isotopes (atoms of the same element that have the same number of protons but a different number of neutrons).

This showed that from around 2.3 million years ago, the environment consisted of a mosaic of dense, rich forests and grasses. This environment, characterized by diverse food and plentiful water sources, provided ideal conditions for G. blacki to thrive alongside other primates.

But by around 700,000-600,000 years ago, the researchers observed a shift towards a more seasonal climate, which sparked changes in plant communities and increased open forest environments. This environment was characterized by less diversity in food sources.

The researchers also analyzed the teeth of G. blacki and Pongo weidenreichi—their closest primate relative—to determine changes in the diet and behavior of the species in this period. This revealed that G. blacki, the ultimate specialist, was not good at adapting to the changing conditions, displaying signs of chronic stress. Meanwhile, the fossil record indicates a decline in the number and geographical spread of G. blacki, with the evidence suggesting that the population was struggling around 300,000 years ago.

On the other hand, P. weidenreichi (the Chinese orangutan) appears to have fared better in the same period, adapting more effectively to the changing environment (although this species would also eventually go extinct around 66-57,000 years ago).

"The more seasonal climate created dry periods when fruits were difficult to find," Westaway said. "G. blacki relied on a less nutritious fallback food, such as bark and twigs. Whereas P. weidenreichi was more flexible in its fallback food, eating shoots, leaves, flowers, nuts, seeds—even insects and small mammals."

"G. blacki's range for foraging was restricted by its size. But P. weidenreichi was more mobile traveling in the canopy for longer distances, allowing a greater range for foraging. G. blacki stayed in the forest whereas P. weidenreichi was able to move into more open forest environments."

The latest findings, thus, shed new light on the demise of the largest primate ever to have roamed the Earth. Ultimately, the struggle of G. blacki to adapt to its changing environment led to the extinction of the great ape, according to the study.

"Understanding the causes of primate extinction is crucial with the threat of a sixth mass extinction event looming over the planet," Westaway said. "Going back to past unresolved extinctions and determining the causes helps us understand why some species are more vulnerable and why others are more resilient."

Enrico Cappellini, a researcher with the Faculty of Health and Medical Sciences at the University of Copenhagen in Denmark, who was not involved in the latest paper, told Newsweek the conclusions of the Nature study look "very convincing" to him.

"In particular it is very useful to have a well defined chronology of the disappearance of G. blacki," he said.

Julien Louys, a paleontologist with Griffith University in Australia, who was also not involved in the study, told Newsweek it was an "impressive" piece of research.

"Although we've suspected for a long time that environmental change was the primary driver of Gigantopithecus extinction, these authors have provided unprecedented detail both in the timing of extinction as well as the ecology of [the species] and local environmental changes," he said. "These data provide a convincing case for loss of suitable habitat as cause of the extinction of this giant ape.

"This has implications for understanding the extinction of megafauna in Southeast Asia, and more broadly, globally."

Update 1/17/24, 6:33 a.m. ET: This article has been updated with comments from Enrico Cappellini and Julien Louys.