Long before humans arrived on the Asian continent and the legend of the Yeti became famous, in the southern plains of present-day China there lived a hominoid primate about three meters tall and weighing about 250 kilos, which, according to known so far, can be considered the largest ape that has ever existed.
This very distant ancestor of humans, which has now been assigned the scientific name Gigantopithcus blacki, became extinct without the causes being determined so far. The enigma may have been solved after the study of some 2,000 fossilized teeth and four jaws, the best memories of its existence.
The results of this research led by Yinggi Zhang (Chinese Academy of Sciences and Macquarie University, Australia) and Renaud Joannes-Boyau (Chinese Academy of Sciences and University of Johannesburg, South Africa) are presented in the journal Nature (10 January). The authors calculate that the largest primate that has walked the Earth became extinct between 295,000 and 215,000 years ago due to the inability to adapt its diet and behavior to the environmental and climatic changes of its time.
"The story of G. blacki is an enigma in paleontology: how could such a powerful creature become 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-senior author Professor Yingqi Zhang of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences (IVPP).
"The IVPP has been excavating for evidence of G. blacki in this region for more than 10 years, but without solid dating and consistent environmental analysis, the cause of its extinction had escaped us," indicates this expert in a note dissemination by Macquarie University, to which he is also attached.
The definitive evidence revealing the giant ape's extinction story comes from a large-scale project collecting evidence from 22 cave sites spread across a wide region of Guangxi province in southern China. The basis of this study was the dating of the remains found.
"It is a great feat to present a defined cause for the extinction of a species, but establishing the exact moment at which a species disappears from the fossil record gives us an objective time frame for an environmental reconstruction and behavioral assessment," says co-lead author, Kira Westaway, Macquarie University geochronologist, associate professor.
Six Australian universities contributed to the project. Macquarie University, Southern Cross University, University Wollongong and the University of Queensland used multiple techniques to date samples. Southern Cross also mapped the teeth of G. blacki to extract information about ape behavior. ANU and Flinders University studied pollen and fossil sediments from the cave, respectively, to reconstruct the environments in which G. blacki thrived and then disappeared.
The work that is now published details that they have applied six different dating techniques to the sediments and fossils of the cave in which the most important remains of this species were found, 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 evidence of G. blacki was found.
Luminescence dating, which measures a light-sensitive signal found in the funerary sediments encasing the G. blacki fossils, was the primary technique, supported by uranium series (US) and electron spin resonance (US-ESR). of the dating of G. black teeth themselves.
"By directly dating the fossil remains, we confirm that their age aligns with the luminescence sequence in the sediments where they were found, giving us a complete and reliable chronology for the extinction of G. blacki," says Associate Professor Renaud, geochronologist at Southern Cross University. Joannes-Boyau.
Using detailed pollen analyses, faunal reconstructions, stable isotope analysis of teeth, and detailed micro-level analysis of cave sediments, the team established the environmental conditions that led to the extinction of G blacki. Then, using trace elements and dental microwear texture analysis (DMTA) of the apes' teeth, the team modeled the behavior of G. blacki while it was flourishing, compared to the behavior during the species' demise.
"Teeth provide amazing insight into species behavior, indicating stress, diversity of food sources and repeated behaviors," says Associate Professor Joannes-Boyau.
The findings show that G.blacki became extinct between 295,000 and 215,000 years ago, much earlier than previously assumed. Before that time, G. blacki flourished in a rich and diverse forest.
Between 700,000 and 600,000 years ago, the environment became more variable due to the increasing strength of the seasons, causing a change in the structure of forest communities.
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 not available, decreasing its food diversity. The ape became less mobile, had a reduced geographic range to forage, and faced chronic stress and dwindling numbers.
"G. blacki was the ultimate specialist, compared to more agile adapters like orangutans, and this ultimately led to its demise," says Professor Zhang.
Associate Professor Westaway says: "With the threat of a sixth mass extinction looming, there is an urgent need to understand why species become extinct.
"Exploring the reasons for past unresolved extinctions gives us a good starting point for understanding the resilience of primates and the fate of other large animals, in the past and in the future."
