Fossils of archaic human found in a cave are the same sex. Scientists want to learn why

Key Points:

• Researchers analyzing ancient proteins from 20 Homo naledi teeth found in South Africa's Rising Star cave system discovered that all samples belonged to females, an unexpected finding that challenges previous assumptions about the species' sexual dimorphism and burial practices.
• The absence of male-specific amelogenin proteins suggests either a sex bias in mortuary rituals, with Homo naledi possibly burying only females, or a rare genetic mutation deleting the male amelogenin gene, though the latter is considered unlikely across so many individuals.
• Experts remain divided on interpretations: some propose that the female-only remains indicate deliberate sex-segregated burial customs, while others caution that natural behaviors, such as female-only foraging groups or shelter use, could explain the pattern without implying advanced cognitive abilities.
• The findings raise new questions about Homo naledi's social structure, behavior, and evolution, highlighting the species' unique characteristics and the complexity of interpreting fossil evidence from this enigmatic hominin.