Researchers have analyzed proteins from 2-million-year-old teeth of Paranthropus robustus, revealing unexpected genetic variations and sex differences among the fossils. This paleoproteomics study suggests the species may represent a mix of populations rather than a single uniform group. The findings provide some of the oldest molecular data from African hominin fossils.
Paranthropus robustus, a robust hominin cousin of early humans known for its powerful jaws and thick tooth enamel, has fascinated scientists since its fossils were first discovered in 1938. Adapted for chewing tough foods, this upright-walking species lived in southern Africa from about 2.25 million to 1.7 million years ago. South Africa's rich fossil record, including sites like Swartkrans Cave in the Cradle of Humankind, has preserved remains of various early human relatives, from Australopithecus species to later Homo forms, marking key evolutionary steps like bipedalism, tool use, and brain expansion.
Traditional genetic analysis has been challenging due to the poor preservation of ancient DNA in Africa's warm climate. To address this, a team of African and European scientists, including principal investigators Jesper V. Olsen, Rebecca R. Ackermann, and Enrico Cappellini, employed paleoproteomics—the study of ancient proteins. They extracted proteins from the enamel of four P. robustus teeth from Swartkrans Cave. Proteins, which bind tightly to enamel and resist decay better than DNA, yielded viable molecular data over 2 million years old.
The analysis determined the sex of the individuals: two males and two females. More strikingly, it uncovered variations in the enamelin gene, which produces a key enamel-forming protein. Two fossils shared an amino acid sequence common to humans, chimpanzees, and gorillas, while the others had a unique version seen only in Paranthropus. One specimen even showed heterozygosity, carrying both variants—the first such evidence in proteins this ancient.
These genetic differences challenge the view of P. robustus as a single species, hinting at diverse ancestries within the population. By integrating this molecular data with morphological studies, researchers aim to refine the early hominin family tree. The team, which included local African experts, followed strict regulations to minimize damage to the fossils, promoting decolonized paleontology and building regional capacity.
Future analyses of more P. robustus specimens from other South African sites could confirm these insights, offering a fuller picture of human evolutionary complexity.