Ancient tooth enamel proteins reveal hidden diversity in African Paranthropus

American Association for the Advancement of Science (AAAS)—Analysis of ancient proteins preserved in fossilized tooth enamel reveals insights into the elusive nature of Paranthropus robustus, researchers report*. The findings, which challenge long-held assumptions about this early human relative, suggest greater diversity within Paranthropus than previously recognized and support the possibility of multiple distinct species within the genus. While advances in ancient DNA (aDNA) sequencing have enabled valuable insights into the evolutionary relationships of Middle to Late Pleistocene hominins, understanding of earlier Pliocene-Pleistocene species, like Paranthropus, remains limited. This is largely because aDNA does not survive well in African hominin fossils older than 20,000 years of age. Paranthropus, which lived between 2.8 and 1 million years ago alongside other early hominins like Australopithecus and Homo, has traditionally been viewed as a single evolutionary group. However, overlapping traits between Paranthropus robustus and Australopithecus africanus have raised questions about their potential evolutionary relationship. Moreover, variation in tooth structure suggests either hidden diversity within P. robustus or the presence of multiple separate species.

In lieu of aDNA, Palesa Madupe and colleagues used ancient proteins – which can persist far longer – to investigate variation within this ancient hominin species. Using high-resolution mass spectrometry and paleoproteomics techniques, Madupe et al. analyzed dental enamel proteins from four P. robustus fossils found in South Africa’s Swartkrans cave. These fossils, dated to between 1.8–2.2 million years ago, represent some of the earliest known of this species. Protein sequence analysis revealed molecular-level variation among the P. robustus individuals, including evidence of both male and female specimens – challenging the reliability of tooth-size-based sexing and suggesting that sexual dimorphism alone cannot account for the observed diversity in the fossil record. Notably, one individual appears genetically distinct from the others, which may indicate the presence of a different Paranthropus group or reflect substantial intraspecific variation. According to the authors, these findings align with recent morphological evidence pointing to previously unrecognized taxonomic diversity within the genus, including the proposed species P. capensis.

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Article Source: AAAS news release.