Enamel Proteome shows that Gigantopithecus was an early diverging pongine.

Abstract

Gigantopithecus blacki was a giant hominid that inhabited densely forested environments of Southeast Asia during the Pleistocene ¹ . Its evolutionary relationships to other great ape species, and their divergence during the Middle and Late Miocene (16-5.3 Mya), remains disputed ^{2, 3} . Hypotheses regarding relationships between Gigantopithecus and extinct and extant hominids are difficult to substantiate because of its highly derived dentognathic morphology and the absence of cranial and post-cranial remains ^{1, 3- 6} . Therefore, proposed hypotheses on the phylogenetic position of Gigantopithecus among hominids have been wide-ranging, but none have received independent molecular validation. We retrieved dental enamel proteome sequences from a 1.9 million years (Mya) old Gigantopithecus blacki molar found in Chuifeng Cave, China ^{7, 8} . The thermal age of these protein sequences is approximately five times older than any previously published mammalian proteome or genome. We demonstrate that Gigantopithecus is a sister clade to orangutans (genus Pongo) with a common ancestor about 10-12 Mya, implying that the Gigantopithecus divergence from Pongo is part of the Miocene radiation of great apes. Additionally, we hypothesize that the expression of alpha-2-HS-glycoprotein (AHSG), which has not been observed in enamel proteomes previously, had a role in the biomineralization of the thick enamel crowns that characterize the large molars in the genus ^{9, 10} . The survival of an Early Pleistocene dental enamel proteome in the subtropics further expands the scope of palaeoproteomic analysis into geographic areas and time periods previously considered incompatible with genetic preservation.