RISING STAR CAVE SYSTEM — A study published in the journal Cell on June 24, 2025, reports that genetic analysis of dental proteins from 23 Homo naledi teeth revealed all individuals sampled were genetically female. The findings suggest possible cultural sex-based burial practices among Homo naledi.

Palesa Madupe, a molecular scientist at the Max Planck Institute for Evolutionary Anthropology, and her colleagues analyzed proteins in dental enamel from teeth collected from at least 20 different individuals, ranging from infants to older adults. All 23 tooth samples contained the protein amelogenin-X (AMELX), which is encoded on the X-chromosome. None of the samples contained the protein AMELY, typically present in genetically male humans and encoded on the Y-chromosome.

Madupe and her colleagues stated that they should have been able to detect AMELY if it were present, given the level of AMELX in the samples. The probability of all sampled individuals being female by chance is approximately 0.0000954 percent. Every known Homo naledi skeleton for which teeth were available in the Rising Star Cave System is genetically female. Lee Berger, a National Geographic explorer-in-residence and co-author, described the results as surprising. "This was no longer chance, at this point," Berger said. "I think it is fair to say that they surprised us."

Berger suggested cultural selection after death for burial by sex and perhaps gender as the most likely reason for these results. "H. naledi has always been an enigmatic discovery," Berger said. "The most likely reason for these robust results are, in my opinion, cultural selection after death for burial by sex and perhaps gender."

Enrico Cappellini, a paleoproteomics researcher at the University of Copenhagen and co-author, stated that an absence of Homo naledi males in the cave system or a systematic deletion of their AMELY gene would have deep implications for understanding the species' biology and evolution. "It is very unlikely that this would be the case among even half of the 20 individuals we studied or for an entire population," Cappellini said. "Either scenario, namely the absence of H. naledi males in the Rising Star cave system or a systematic deletion of their AMELY gene, is fascinating and would have deep implications for a better understanding of the biology and evolution of this species."

The Homo naledi remains unearthed in the Rising Star Cave System are between 335,000 and 236,000 years old. Lee Berger led the team that unearthed the remains of more than 20 small-bodied hominins from the Rising Star Cave System in South Africa in 2013.