These very distant primate relatives (Gigantopithcus blacki) went extinct before humans arrived in the region; there are few clues as to why, and so far the only signs of their existence are about 2,000 fossilized teeth and four jaw bones.
New findings from the region show beyond a shadow of a doubt that the largest living primate on Earth went extinct between 295,000 and 215,000 years ago, vulnerable to changing climates and unable to adapt its food preferences and behavior.
“The story of G. blacki is an enigma in paleontology,” said paleontologist Yingqi Zhang, co-author of the study. How could such a powerful creature go extinct at a time when other primates were adapting and surviving? The unsolved reason for its disappearance has become a riddle.”
“Researchers have been excavating for evidence of G. blacki at this site for over 10 years, but without precise dating and a consistent environmental analysis, we have been unable to find the cause of its extinction.”
The definitive evidence to tell the story of the giant primate’s extinction came from a large-scale project that collected evidence from 22 cave sites spread across a large area of Guangxi Province in southern China. The basis of this work was dating.
“Establishing the precise cause of a species’ extinction is a major achievement, but determining the exact time when a species disappeared from the fossil record gives us a target time frame for environmental reconstruction and behavior assessment,” says Kira Westaway, associate professor of geochronology and co-author of the study.
“Without a solid dating, you are looking for clues in the wrong places.”
In collaboration with six universities, multiple techniques were used to date the samples. In addition, G. blacki teeth were mapped to obtain information about the apes’ behavior. Then, pollen and fossil-bearing sediments from the cave were analyzed to reconstruct the environments in which G. blacki reproduced and then disappeared.
Six different dating techniques were applied to cave sediments and fossils, yielding 157 radiometric ages. These were combined with eight pieces of environmental and behavioral evidence and applied to 11 caves containing evidence of G. blacki, as well as 11 caves of similar age range without evidence of G. blacki.
Luminescence dating, which measures a light-sensitive signal found in sediments covering G. blacki fossils, was the primary technique, supplemented by uranium series and electron spin resonance dating of G. blacki teeth.
“By directly dating the fossil remains, we confirmed that their age is consistent with the luminescence sequence in the sediments in which they were found, providing us with a comprehensive and reliable chronology of the extinction of G. blacki,” says geochronologist Associate Professor Renaud Joannes-Boyau.
Using detailed pollen analysis, faunal reconstructions, stable isotope analysis of teeth and detailed micro-level analysis of cave sediments, the team identified the environmental conditions that led to the extinction of G. blacki. Then, using trace element and microwear textural analysis of the primates’ teeth, the team modeled G. blacki’s behavior during its proliferation, comparing it to that during the species’ extinction.
“The teeth provide a surprising insight into the species’ behavior, indicating stress, diversity of food sources and repeated behaviors,” says Associate Professor Joannes-Boyau.
The findings suggest that G. blacki went extinct between 295,000 and 215,000 years ago, much earlier than previously estimated. Before that time, G. blacki was reproducing in a rich and diverse forest.
Between 700,000 and 600,000 years ago, the environment became more variable due to the increased intensity of the seasons, causing a change in the structure of forest communities.
G. blacki’s close relative orangutans (genus Pongo) adapted their size, behavior and habitat preferences as conditions changed. In contrast, G. blacki relied on a less nutritious backup food source when its preferences were not available, reducing dietary diversity. The primate became less mobile, had less geographic space to forage, and faced chronic stress and dwindling numbers.
“G. blacki was an expert on one food compared to animals that can adapt more quickly, such as orangutans, and this ultimately led to its demise,” says Professor Zhang.
“As the threat of a sixth mass extinction looms over us, we urgently need to understand why species are disappearing,” says Associate Professor Westaway.
“Investigating the causes of past unsolved extinctions gives us a good starting point for understanding the resilience of primates and the past and future fate of other large animals.”
Source: Zhang, Y., Westaway, K.E., Haberle, S. et al. (2024). The demise of the giant ape Gigantopithecus blacki. Nature.
