Now We Know Why The Largest Primates to Ever Live Went Extinct

Giants once roamed the karst plains of southern China, three-meter tall apes weighing in at over 550 pounds (250 kilograms). Gigantopithcus blacki – a very distant human ancestor – went extinct before humans arrived in the region, with few clues as to why. Around 2000 fossilized teeth and four jawbones have been the only signs of their existence so far.

New evidence from this region uncovered by a team of Chinese, Australian, and U.S. researchers has solved the mystery of why G. blacki disappeared.

A Changing Climate and Inability to Adapt

Their research, published in Nature,  demonstrates beyond doubt that the largest primate to walk the earth went extinct between 295,000 and 215,000 years ago. It shows that G. blacki's inability to adapt its food preferences and behaviors and vulnerability to the changing climates sealed its fate.

A Long-Standing Mystery

“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,” says paleontologist and co-lead author Professor Yingqi Zhang from the Institute of Vertebrate Palaeontology and Palaeoanthropology at the Chinese Academy of Sciences (IVPP).

“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.”

Evidence Was Collected From 22 Caves

Definitive evidence explaining the reasons for the giant ape’s extinction comes from a large-scale project collecting evidence from 22 cave sites. The caves are spread across a wide region of Guangxi Province in southern China. The foundation of this study was dating.

Six Australian universities contributed to the project. Macquarie University, Southern Cross University, Wollongong University, and the University of Queensland used multiple techniques to date samples. Southern Cross also mapped G. blacki teeth to extract information on the apes’ behaviors. ANU and Flinders University studied the pollen and fossil-bearing sediments in the cave, respectively, to reconstruct the environments in which G. blacki thrived and then disappeared.

Making Connections to Environmental Factors

“It’s a major feat to present a defined cause for the extinction of a species, but establishing the exact time when a species disappears from the fossil record gives us a target timeframe for an environmental reconstruction and behavior assessment,” says co-lead author, Macquarie University geochronologist Associate Professor Kira Westaway.

Six Different Dating Techniques Used

“Without robust dating, you are simply looking for clues in the wrong places.”

Six different dating techniques were applied to the cave sediments and fossils, producing 157 radiometric ages. These were combined with eight sources of environmental and behavioral evidence and applied to 11 caves containing evidence of G blacki, and also to 11 caves of a similar age range where no G. blacki evidence was found.

Dating Established Environmental Conditions Leading Up to Extinction

 

Using detailed pollen analysis, fauna reconstructions, stable isotope analysis of the teeth, and a detailed analysis of the cave sediments at a micro level, the team established the environmental conditions leading up to when G blacki went extinct.

Luminescence dating, which measures a light-sensitive signal found in the burial sediments that encased the G. blacki fossils, was the primary technique, supported by uranium series (US) and electron-spin resonance (US-ESR) dating of the G. blacki teeth themselves.

Teeth Provide Insights

 

Using trace element and dental microwear textural analysis (DMTA) of the apes’ teeth, the team modeled G. blacki’s behavior while it was flourishing, compared to during the species’ demise.

“Teeth provide a staggering insight into the behavior of the species indicating stress, diversity of food sources, and repeated behaviors,” says Associate Professor Joannes-Boyau

Evidence Shows Extinction Occurred Earlier That Originally Believed

 

The findings show G.blacki went extinct between 295,000 and 215,000 years ago, much earlier than previously assumed. Before this time, G. blacki flourished in a rich and diverse forest.

By 700,000 to 600,000 years ago, the environment became more variable due to the increase in the strength of the seasons, causing a change in the structure of the forest communities.

G. blacki Didn't Adapt to Changing Conditions

Orangutans (genus Pongo) – a close relative of G. blacki – adapted their size, behavior, and habitat preferences as conditions changed. In comparison, G. blacki relied on a less nutritious backup food source when its preferences were unavailable, decreasing the diversity of its food. The ape became less mobile, had a reduced geographic range for foraging, and faced chronic stress and dwindling numbers.

“G. blacki was the ultimate specialist, compared to the more agile adapters like orangutans,  and this ultimately led to its demise,” says Professor Zhang.

An Urgent Need to Understand Why Species Go Extinct

Associate Professor Westaway says: “With the threat of a sixth mass extinction event looming over us, there is an urgent need to understand why species go extinct.

“Exploring the reasons for past unresolved extinctions gives us a good starting point to understand primate resilience and the fate of other large animals, in the past and future.”

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