Remains of the Giant Pongine Ape Gigantopithecus blacki are known from Early to Middle Pleistocene cave deposits from China south of the Yangtze River. It is considered to have been a key member of two successive faunal zones in the region, the Gigantopithecus–Sinomastodon and Stegodon–Ailuropoda zones, which together cover the time period from about 2 million years ago to about 330 000 years ago. Gigantopithecus blacki is estimated to have stood about 3 m tall, and to have weighed 200-300 kg, making it the largest Primate ever known, although it is known only from four mandibles and about 2000 isolated teeth. It had unusually large molars, with exceptionally thick enamel, with the first specimens coming to the attention of scientists being found in an apothecary's shop in Hong Kong as 'Dragon's teeth', with a subsequent search finding remains in several caves in the Chongzuo area and the Bubing Basin of Guangxi Province, China.
Very few of these sites have been subject to rigorous dating, making the timeline for Gigantopithecus blacki somewhat uncertain. The oldest remains attributed to the species were deposited about 2.2 million years ago at Baikong Cave, while the youngest remains date from between 420 000 and 330 000 years ago at Hejiang Cave. Over this time, the teeth of Gigantopithecus blacki increased in size and became more complex (gained more features on the surface of the molars, which would have increased its ability to grind hard foods), which suggests its diet was changing in response to new ecological pressures. Gigantopithecus blacki is thought to have been a specialized herbivore, feeding on abrasive foods which it was able to process with its large jaws and molars, and consuming a large amount of fruit. At the time when the Baikong Cave deposits were laid down, a diverse forest ecosystem supporting a range of Primates covered much of what is now Guangxi, Guizhou, Hainan and Hubei provinces. By the time the Hejiang Cave deposits were being laid down, Gigantopithecus blacki was found only in Guangxi. The reasons why Gigantopithecus blacki underwent first a decline in range and then went extinct have been debated extensively, but not studied in detail, with most studies of the species concentrating on single sites and not incorporating behavioural and environmental evidence.
In a paper published in the journal Nature on 10 January 2024, a team of scientists led by Yingqi Zhang and Kira Westaway of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, and the School of Natural Sciences at Macquarie University, examined cave deposits from 22 sites in the Chongzuo area and the Bubing Basin that had produced and not produced remains of Gigantopithecus blacki, in order to date the deposit sequences, look for palaeoclimate proxies, and evidence for the behaviour of Gigantopithecus blacki.
Eleven of the caves examined by Zhang et al. have yielded remains attributed to Gigantopithecus blacki, while the remaining eleven have not. Six independent dating methods were used at each of these sites, in order to establish a reliable timeline for the sequences allowing comparison between sites. Finally, isotope and wear analysis of teeth was used to determine changes in the diet of Gigantopithecus blacki over time.
The methods enabled the development of a sequence that lasted from about 2.3 million years ago to about 49 000 years ago. This provided a timeline for the presence of Gigantopithecus blacki which lasted from 2.3 million years ago to 255 000 years ago, suggesting that in order to understand the extinction of the species, the interval 295 000 to 215 000 should be studied in greater detail. Thus Zhang et al. split the sequence into four segments, a pre-extinction phase from 2.3 million to 700 000 years ago, a transition phase from 700 000 to 295 000 years ago, an extinction window phase, from 295 000 to 215 000 years ago, and a post-extinction phase, from 215 000 years ago to the present.
Pollen analysis reveals that during the pre-extinction phase the dominant flora of the region were trees, particularly members of the Pinaceae, Fagaceae and Betulaceae (Pines, Beaches and Birches), with patches of grassland also present. During the transition phase this changed, with a greater proportion of disturbance taxa (i.e. species which colonise disturbed sites rapidly), which persisted through the extinction window phase. After the extinction window, from about 200 000 years ago onwards, the flora became dominated by Ferns and Grasses, with some trees, such as Mulberries and Podocarps, still present.
The fauna of the region in the pre-extinction phase was characterised by relatively large numbers of Gigantopithecus blackii, as well as the early Panda Ailuropoda microta, Baboon-like Monkeys of the genus Procynocephalus, the Elephants Sinomastodon and Stegodon, the Chalcothere Hesperotherium, and the Pig Hippopotamodon. During the transition and extinction window phase, the numbers of Gigantopithecus blackii dwindled, Ailuropoda microta was replaced by the more modern Ailuropoda baconi, and while Stegodon persisted, Sinomastodon was replaced by Elephas, the genus to which all modern Asian Elephants belong.
The proportion of carbon isotopes in the teeth of Gigantopithecus blackii shifts from the pre-extinction phase into the extinction window, suggesting a change in diet. Interestingly, the carbon isotope ratio of the teeth of the Baboon-like Monkeys Procynocephalus weidenreichi, is similar to that of Gigantopithecus blackii in both phases, suggesting that it underwent a similar dietary change. However, Procynocephalus weidenreichi persisted after the extinction of Gigantopithecus blackii, and the carbon isotope ratios of its teeth underwent a much greater shift at about this time, suggesting another, larger dietary shift, which Gigantopithecus blackii was not capable of making.
The proportion of the elements strontium, barium, and lead in the tooth enamel of Gigantopithecus blackii also changed from the pre-extinction phase into the extinction window, again suggesting a dietary shift.
The pollen-data suggests that in the pre-extinction phase the study area was covered by a mosaic of open woodland and grasslands, but that in the transition and extinction window phases this suffered a climate breakdown, with increasing seasonality, and a shift to a drier environment, with more shrubs and grassland, and probably a much more seasonal water-cycle, with distinct wet and dry seasons.
A decline in forest cover during this interval has been recorded across a wide area of China, Southeast Asia, and Australasia. However, the problem for Gigantopithecus blackii seems to have been not the overall decline in forests, so much as the rise in environmental variability and the associated rise in the dominance of disturbance taxa. The isotope and trace element data suggests that both Gigantopithecus blackii and Procynocephalus weidenreichi lived in closed canopy forested environments, and had a highly diverse diet, including seasonal fruits and flowers and periodic water consumption. A subtropical climate with minimal seasonal variation would have ensured a variety of foods year-round, enabling these species to rely on a mixture of forest Plants for food. Once the climate began to shift, the range of Plant foods available became much more restricted and seasonal, and fresh drinking water was probably not available year round either, causing considerable stress to the Gigantopithecus blackii population. Procynocephalus weidenreichi appears to have been able to survive this change by shifting its diet to incorporate foods from the new environment, something Gigantopithecus blackii was apparently unable to do. The microwear on the teeth of both species increases over this interval alters, probably reflecting a reduced fruit availability, and a greater reliance on more fibrous foods, which ultimately appears to have proven to poor a diet for Gigantopithecus blackii.
Zhang et al.'s study provides a timeline for the flourishing and subsequent demise of Gigantopithecus blackii, a specialist forest-dwelling Ape, reliant on a rich evergreen-deciduous forest with plenty of available water. Once the climate began to change in the area, and the faunal and floral composition of the forests began to shift, Gigantopithecus blackii began to suffer dietary stress, leading to a decline in population and eventual extinction.
Unlike the Baboon-like Procynocephalus weidenreichi, with which it shared its forest environment, Gigantopithecus blackii was apparently unable to adapt to a changing environment, probably because of a greater relaince on fruits, as well as a larger body-size, which would probably have made it less mobile, and more dependent on the forests maintaining a stable structure. Gigantopithecus blackii is also likely to have been entirely terrestrial, with a limited range, albeit with a willingness to travel to find water. Procynocephalus weidenreichi, on the other hand, is thought to have been more able to venture into the treetops, enabling it to reach food and water sources which would have been unavailable to Gigantopithecus blackii. Unlike Gigantopithecus blackii, which appears to have grown larger over the course of the Pleistocene, Procynocephalus weidenreichi became smaller, and therefore presumably more agile, enabling it to reach less readily available food sources, as well as requiring less food overall. This greater adaptability appears to have enabled the Monkey to survive while the larger Ape was unable.
The population of Gigantopithecus blackii appears to have been struggling by about 300 000 years ago, with both the number of inhabited caves and number of teeth per cave (which would have reflected the number of Apes) reduced. From this time onwards, populations of Gigantopithecus blackii appear smaller and more stressed, as the number of forest refugia available to them diminished. Notably, and unlike many other Pleistocene species in Asia and Australasia, the decline of Gigantopithecus blackii appears to have been unrelated to the spread of Homo sapiens, or other Hominin species.
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