Ancient Teeth Unveil Oldest Human Genetic Data
In a groundbreaking discovery, scientists have extracted genetic information from preserved teeth belonging to a prehistoric human species that lived in South Africa more than two million years ago. This remarkable feat has shed light on how this long-extinct creature fits into the human family tree, providing the earliest genetic data ever obtained from any hominid.
Overcoming Obstacles and Revealing Evolutionary Connections
The researchers, whose findings are detailed in an unpublished study, state that no African hominid sample older than 18,000 years had ever yielded ancient DNA. Overcoming this obstacle, they present protein sequencing data from the tooth enamel of four members of the species Paranthropus robustus, each living approximately 2.42 million years ago.
Swartkrans Cave: A Time Capsule of Prehistory
The teeth were discovered in the Swartkrans cave, located 40 km (25 miles) northwest of Johannesburg. It is believed that rapid floods caused these remains to gather in the cave, where “extensive cementation” helped preserve the enamel proteins over millions of years. This remarkable preservation allowed scientists to sequence hundreds of amino acids in each tooth using mass spectrometry, providing crucial insights into the evolutionary connections between P. robustus and other hominids.
Unraveling the Human Family Tree
According to the study’s authors, “the sequences we were able to recover put Paranthropus both within the clade of hominins and as an outgroup to the clade encompassing Homo sapiens, Neanderthals, and Denisovans.” This revelation places the ancient South African species as a distant relative of the more closely related species that arose in Eurasia in the past few hundred thousand years, including modern humans, while still firmly establishing it as a member of the human family.
Intriguing Genetic Diversity
Intriguingly, one of the four individuals analyzed “may be more distantly connected to the other three individuals than they are to each other,” according to the researchers. While unable to confirm it definitively, they speculate that this outlier may have even belonged to a distinct Paranthropus group.
Challenging Assumptions and Revealing Insights
Remarkably, the study authors were able to identify two of the specimens as males, despite one of them previously being classified as female based on bone size, thanks to the discovery of a protein encoded by a gene found only on the Y-chromosome. The other two individuals, who were female, exhibited higher levels of the X-chromosome variant of this protein.
A Game-Changing Advancement for Paleoanthropology
While the genetic data gathered is ultimately insufficient to accurately place P. robustus within the human family tree or sort out all of its evolutionary relationships, the researchers acknowledge that “the recovery of [two-million-year-old] phylogenetically informative genetic material in African hominins can be regarded as a potentially game-changing advancement for paleoanthropology.”
