The largest primates ever to walk the Earth went extinct about a quarter of a million years ago because they struggled to adapt their food habits to environmental changes, a new study has found.
The Gigantopithecus blacki – a very distant human ancestor – stood as tall as 3 metres (nearly 10 feet) and weighed up to 300kg (660 pounds). They used to be found in Southeast Asia including southern China between 2 million and 330,000 years ago.
But the giant apes disappeared well before humans arrived in the karst plains of today’s Guangxi province, according to the study into their mysterious demise led by Chinese and Australian researchers.
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The findings of the study were published in the peer-reviewed journal Nature on Thursday.
“The story of G. blacki is an enigma in palaeontology – how could such a mighty creature go extinct at a time when other primates were adapting and surviving?” said Zhang Yingqi, a professor at the Chinese Academy of Sciences’ Institute of Vertebrate Palaeontology and Palaeoanthropology and co-lead author of the study.
The team, also comprising researchers from Germany, South Africa, Spain and the United States, looked at evidence collected from 22 cave sites spread across a wide region of Guangxi.
“G. blacki was the ultimate specialist and, when the arboreal environments changed, its struggle to adapt sealed its fate,” the team said in the Nature article.
They established beyond doubt that the G. blacki went extinct in the late middle Pleistocene era, much earlier than previously assumed.
Moreover, the reason for the apes’ demise was a failure to adapt their eating habits and behaviour, compared to “more agile adaptors like orangutans”, the team found.
“Establishing the exact time when a species disappears from the fossil record gives us a target time-frame for an environmental reconstruction and behaviour assessment,” Macquarie University geochronologist and associate professor Kira Westaway, the other lead author, said.
The species used to flourish in dense forests with heavy cover, with year-round access to water and limited seasonal changes in their diet.
Around 700,000 to 600,000 years ago, seasonality became stronger and open forests dominated the landscape of today’s southern China, reducing diversity in food sources, the team found.
Failing to find their preferred food, the G. blacki turned to less nutritious backup sources. The species became less mobile and had a narrower foraging range, they showed signs of chronic stress and their numbers dwindled.
They eventually became extinct between 295,000 and 215,000 years ago.
“We are very proud to be able to solve the mystery,” Zhang said. “How it went extinct could be a good lesson as the planet faces the sixth mass extinction event, driven by human activities.”
In contrast, the closely related orangutan (genus Pongo) thrived as they were able to adapt their size, behaviour and habitat preferences as conditions changed. The highly intelligent apes only found in Asia share almost 97 per cent of human DNA. However, only three species have survived into the modern age.
Even the Chinese orangutan (Pongo weidenreichi), native to southern China, was able to survive for a further 200,000 years or so, as the youngest fossils date back to between 66,000 and 57,000 years ago.
“When the G. blacki was thriving, the dense forest provided them with fruits everywhere they roamed all year round. It was great living conditions for them – they did not have to worry about food,” Zhang said.
“But as the environment changed, their preferred food became less available. They then turned to less nutritious choices such as leaves, bark and branches.
“Although they could eat a large amount of these things, it would not meet their nutritional needs for reproduction. The species began to face huge survival pressure. The population shrank, and eventually collapsed.”
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Zhang and his team started excavating and collecting evidence from the 22 caves in Guangxi around a decade ago.
They sampled cave sediment and pollen to reconstruct the environments in which the ape thrived and disappeared, while teeth fossils provided hints on changes in diet and behaviour.
“Species are going extinct rapidly. The story of the giant ape shows us primates’ ability to survive when faced with changing environments. It could help us better protect primates and other large animals,” Zhang said.
The three surviving species of orangutan are found only in the rainforests of Sumatra and Borneo. They face threats like hunting and habitat loss, and are listed by the WWF as either endangered or critically endangered.
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