NEW YORK, NY.- Standing nearly as tall as a basketball hoop and weighing as much as a grizzly bear, Gigantopithecus blacki was the greatest ape to ever live. For more than 1 million years during the Pleistocene, Gigantopithecus roamed southern China. But by the time ancient humans reached the region, Gigantopithecus had vanished.

To determine why these prodigious primates died out, a team of scientists recently analyzed clues preserved in Gigantopithecus teeth and cave sediment. Their findings, published Wednesday in the journal Nature, reveal that these nearly 10-foot-tall apes were most likely doomed by their specialized diet and an inability to adapt to a changing environment.

Paleontologists first discovered Gigantopithecus in the mid-1930s in a Hong Kong apothecary where the ape’s unusually large molars were being hawked as “dragon teeth.” The animal was named to honor Davidson Black, the Canadian scientist who studied the early human ancestor known as Peking man. In the decades since, scientists have unearthed about 2,000 Gigantopithecus teeth and a handful of fossil jawbones from caves throughout southern China.

The dearth of fossilized bones makes reconstructing Gigantopithecus difficult; paleoartists depict the ancient ape as looking like an orangutan (its closest living relative) crossed with a silverback gorilla, but bigger. Nevertheless, the very great ape’s teeth, which are encased in a thick layer of enamel, preserve a wealth of clues to how these enigmatic primates lived and potentially why they died out.

Yingqi Zhang, a paleontologist from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing and an author on the new paper, has studied Gigantopithecus fossils for more than a decade. To determine what drove them to extinction, Zhang needed to nail down exactly when Gigantopithecus disappeared. He teamed up with Kira Westaway, a geochronologist at Macquarie University in Australia.

“Establishing exactly when Gigantopithecus drops out of the fossil record requires accurate dating — otherwise, you are looking for clues to its extinction in the wrong places,” Westaway said.

The team collected and dated material from 22 caves across southern China. To fine-tune the ages of the fossils and the cave sediments, the researchers applied six dating techniques. They also analyzed isotopes and pollen in the samples to recreate what the region’s environment was like around the time Gigantopithecus disappeared. Finally, they compared wear patterns in the oversized teeth with fossilized teeth from Pongo weidenreichi, an extinct orangutan that lived alongside Gigantopithecus.

Gigantopithecus, they say, went extinct between 295,000 and 215,000 years ago. Those dates were much more recent than previous estimates and coincide with a dynamic period of environmental change.

The pollen samples revealed that before that extinction window, the local environment was dominated by evergreen trees that created closed-canopy forests. Gigantopithecus appeared to be well-suited to those environments. Analysis of isotopes in Gigantopithecus teeth from that period revealed that the apes were eating fibrous plants, fruits and flowers.

Beginning around 600,000 years ago, the region’s climate began to change with the seasons as dense forests gave way to a patchwork of open forests and grasslands. That led to “dry periods when fruits were difficult to find,” Westaway said. As opposed to ancient orangutans, which adapted by eating a diverse diet of shoots, nuts, seeds and even insects, Gigantopithecus switched to less nutritious alternatives like bark and twigs. Their teeth from this period show signs of chronic stress.

As the environment became unfavorable, Gigantopithecus’ size began to work against it. Unlike spry orangutans, which could travel greater distances through the canopy and into open environments to forage, ground-bound Gigantopithecus were most likely restricted to shrinking patches of forest.

According to Sergio Almécija, a paleoanthropologist at the American Museum of Natural History who was not involved in the new research, the demise of Gigantopithecus reveals that even the largest animals are vulnerable to becoming too specialized.

“These apes became so specialized to living in a specific environment that once that environment changes, they’re gone,” he said.

Modern orangutans are facing a fate similar to that of their giant relatives. While their ancestors were able to adapt to a changing environment, these arboreal specialists are threatened by deforestation. “Their forests are getting smaller and smaller, and each year we have fewer and fewer orangutans,” Almécija said.

This article originally appeared in The New York Times.