In a pioneering scientific breakthrough, researchers have successfully extracted genetic information from an African hominin that existed two million years ago, marking the oldest genetic data ever recovered. The protein sequences, detailed in a preprint published on the bioRxiv server, were derived from several tooth fossils belonging to Paranthropus Robustus, discovered in a South African cave.
Scientists have hailed these genetic findings as astonishing. Katerina Douka, an archaeological scientist at the University of Vienna, describes the results as “amazing” considering that the remains had reached a stage of near petrification due to their age. The recovery of genetic data from such ancient hominin fossils opens up new possibilities, pushing the genetic record back to previously unimaginable times and locations.
While the retrieval of genetic sequences from extremely old fossils presents an exciting development, it remains uncertain how useful this newfound information will be in unraveling long-debated evolutionary relationships. Beatrice Demarchi, a biomolecular archaeologist at the University of Turin, Italy, acknowledges that the usefulness of these sequences is yet to be determined, emphasizing the need for further exploration and analysis.
Preservation of Proteins
Compared to DNA, proteins tend to exhibit higher resilience, enabling researchers to extend the molecular record even further back in time. In 2016, Demarchi’s team achieved a breakthrough by obtaining protein sequences from 3.8-million-year-old ostrich (Struthionidae) eggshells found in Tanzania. Subsequently, a team led by Enrico Cappellini at the University of Copenhagen successfully sequenced tooth proteins from 800,000-year-old Homo antecessor remains in Spain and limited sequences from 1.8-million-year-old Homo erectus fossils in Georgia.
In the recent 2023 study, Cappellini and his colleagues at the University of Copenhagen focused on four P. Robustus teeth recovered from Swartkrans cave near Johannesburg. Using mass spectrometry, the researchers analyzed hundreds of amino acids in the enamel of each tooth sample. The identification of a specific protein, amelogenin-Y, produced by a gene on the Y chromosome, allowed them to determine the sex of two of the teeth as male, challenging the previous assumption that one of the teeth belonged to a female due to its small size. The presence of amelogenin-X protein in the other two teeth suggested their female origin.
The sequencing of approximately 400 amino acids in all four samples facilitated the construction of a basic evolutionary tree. The results confirmed that Homo sapiens, Neanderthals, and Denisovans, hominins found in Siberia, are more closely related to each other within the past 200,000 years than they are to the two-million-year-old Paranthropus. These findings align with expectations and provide valuable insights into the evolutionary relationships among ancient human species.
Cappellini and his team view the creation of an evolutionary tree from genetic data of such ancient remains as a potentially transformative breakthrough for palaeo anthropology. They believe that ancient-protein studies could shed light on the position of Australopithecus afarensis, including the famous fossil specimen known as Lucy, within the hominin family tree. However, other scientists caution that ancient proteins alone may not be sufficient to achieve consensus in understanding hominin evolution, which heavily relies on skeletal characteristics.
Balancing Benefits and Costs
As ancient proteomics continues to expand, researchers stress the importance of carefully considering the benefits against the potential costs of destructive sampling. Pontus Skoglund, a palaeo geneticist at the Francis Crick Institute, is exploring non-destructive methods to assess fossils for protein content, preserving valuable samples that are likely to yield meaningful data. Skoglund emphasizes the need to factor in the risk of failure when deciding how to sample the fossil record.
In summary, the recovery of genetic data from two-million-year-old Paranthropus Robustus fossils represents a significant milestone in scientific research, providing insights into ancient hominin evolution and pushing the boundaries of our understanding of human genetic history.