A study published in the journal Cell reveals that fossilized teeth from Homo naledi, an extinct human relative found in South Africa’s Rising Star cave system, contain no evidence of biological males. By analyzing ancient proteins in the enamel of 20 individuals, researchers determined the absence of the Amelogenin-Y protein, suggesting the group consisted entirely of females or that the species possessed a unique genetic trait.
Why Protein Analysis Is Replacing DNA Research
Scientists are increasingly turning to proteomic analysis because DNA often degrades in the warm, humid climates where many hominin fossils are discovered. According to the research team, tooth enamel is the hardest tissue in the human body, acting as a biological vault that preserves protein sequences for hundreds of thousands of years. While DNA recovery from Homo naledi remains elusive, the examination of 23 teeth provided a stable alternative. By searching for Amelogenin-Y—a protein linked to the male Y chromosome—researchers identified the sex of the individuals without needing a complete genome. This method allows paleoanthropologists to extract biological data from sites previously considered too “ancient” or environmentally compromised for genetic testing.
Tooth enamel is so durable that it can survive geological pressures that crush bone, making it the primary target for future studies on ancient human migration and social structures.
What Does the Absence of Males Suggest About Burial Practices?
The discovery of an all-female group in the Dinaledi Chamber raises the possibility of sex-specific mortuary or burial practices. Researchers note that the statistical probability of randomly sampling 20 individuals and finding only one sex is extremely low. If Homo naledi deliberately placed these individuals in the cave, it would mark one of the earliest known examples of complex ritual behavior in a human relative. This finding builds on previous work by the Rising Star team, which has already proposed that this species used fire and created symbolic engravings, despite having a brain size comparable to a chimpanzee.
How Genetic Deletion Could Change Our Understanding
An alternative theory suggests that Homo naledi may have lacked the gene responsible for the Amelogenin-Y protein entirely. Genetic studies in modern humans and at least one Neanderthal have shown that the Y chromosome can occasionally undergo deletions or alterations. However, the study authors emphasize that it would be highly unusual for such a mutation to manifest across an entire population of 20 individuals. If this were a widespread genetic trait rather than a behavioral choice, it would force a major revision of how scientists interpret sexual dimorphism—the physical differences between males and females—in the human fossil record.
When tracking human evolution, always look for the “sexual dimorphism” index. A lack of size variation in fossils is often the first indicator that researchers should look for sex-specific behaviors rather than assuming a mixed-sex population.
Future Trends in Paleoanthropology
The success of protein analysis in the Rising Star cave signals a shift toward “biomolecular archaeology.” Future research will likely focus on:
- Broadening the Scope: Applying proteomic screening to other archaeological sites where DNA has failed.
- Refining Sex Identification: Developing more sensitive protein markers to identify sub-adults and specific genetic variants.
- Cross-Species Comparisons: Contrasting Homo naledi data with Neanderthal and Denisovan protein profiles to map the evolution of burial rituals.
Frequently Asked Questions
Could the fossils be from a different species?
No. The fossils were recovered from the Dinaledi Chamber, a site definitively linked to Homo naledi since its discovery in 2013.
Is it possible the researchers just missed the males?
The study analyzed 23 teeth from 20 separate individuals. Researchers state that the statistical likelihood of missing all males in a random sample of that size is near zero.
Does this prove they had human-like burials?
It provides strong evidence for intentionality, but scientists are still debating whether this was a burial practice or a different form of body disposal. Evidence of fire and engravings at the same site supports the theory of complex behavior.
What do you think these findings tell us about the social lives of our ancestors? Share your thoughts in the comments below or subscribe to our newsletter for the latest updates on human origins.
