ENVIRONMENTAL DOOM EVER-PRESENT : MASTER GLOBAL ESSAY

Doomed By Environmental Change : The biggest of big apes - but not invulnerable :

Standing nearly as high as a basketball hoop and weighing as much as a large bear, Gigantopithecus blacki was the greatest ape that ever lived.

For more than a million years during the. Pleistocene, Gigantopithecus roamed southern China. But by the time the ancient humans reached the region, Gigantopithecus had vanished.

To determine why these prodigious primates had died out, a team of scientists recently analyzed clues preserved in Gigantopithecus teeth and cave sediment.

Their findings, published in the in the journal Nature, reveal that these nearly 10-foot-tall [ three-meter ] apes were mostly likely doomed by their specialized diet and inability to adapt to a changing environment.

Paleontologists first discovered Gigantopithecus in the mid-1930s in a Hong Kong apothecary shop 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 cades since, scientists have unearthed about 2,000 Gogantopiheceus 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.

But even without bones, its teeth, encased in a thick layer of enamel, preserve a wealth of clues as to how these enigmatic primates lived and possibly why they died out.

Yingqi Zhang, a paleontologist from the Institute of Vertebrate Palaeontology and Palaeoanthropology 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, Dr. Zhang needed to nail down exactly when Gigantopithecus disappeared. He teamed up with Kira Westaway, a geochronologist at Macquarie University in Australia.

They collected and dated material from 22 caves across southern China. To fine-tune the ages of the fossils and the cave sediments, they applied six dating techniques.

They also analyzed isotopes and pollen in the samples to recreate what the environment had been like around the time Gigantopithecus disappeared.

Finally, they compared the wear patterns in oversized teeth from the Pongo weidenreichi, an orangutan that lived alongside Gigantopithecus.

Gigantopithecus, they say, went extinct between 295,000 and 215,000 years ago.

The pollen samples showed that before that extinction window, the local environment had been dominated evergreen trees that created closed-canopy forests.

Gigantopithecus appeared to be well-suited to that environment : analyses of isotopes in its teeth from that period showed that it was eating fibrous plants, fruits and flowers.

Beginning around 600,000 years ago, the region's climate began to change with the seasons, and dense forests gave way to a patchwork of open forests and grasslands.

That led to '' dry periods when fruits were difficult to find,'' Dr. Westaway said. Gigantopithecus switched to less nutritious alternatives like bark and twigs.

As the environment became unfavorable, Gigantopithecus size began to work against it. Unlike spry orangutans, which could travel greater distances through the canopy to forage, Gigantopithecus was most likely restricted to shrinking patches of forest.

The World Students Society thanks Jack Tamisiea.