No Male Markers in 20 Homo naledi Fossils: Was This Cave Women-Only?

How do you read sex from a 240,000-year-old tooth?

The team used a technique called gentle acid etching. In plain terms, they lightly dissolved the surface of fossilized tooth enamel to release tiny protein fragments called peptides, while keeping damage to the irreplaceable fossils to a minimum.

The researchers then searched the samples for Amelogenin-Y, a protein produced from a gene on the male Y chromosome. Across all 23 teeth, they found no evidence of it. Under the simplest reading, none of the individuals were male.

To rule out lab error, specialists at the University of York's chemistry facility analyzed the amino acids in the samples. They confirmed the proteins were genuinely ancient, not contamination from modern handlers or environment.

Enamel made the whole approach possible. Palesa Madupe, who carried out the work during her postdoctoral research at the University of Copenhagen, explained: "Unlike those found in other remains like bone fragments, proteins in tooth enamel are preserved because dental enamel — the hardest tissue in the human body — shields proteins from environmental contamination even for millions of years."

She added: "Our study helps in the long-standing mystery of why Homo naledi lacked significant variation; it's probably because they could have all belonged to one sex."

What are the alternative explanations?

The researchers are careful to hedge their conclusions. An all-female burial site is not the only reading of the data.

The alternative involves the genetics of Homo naledi itself. If the population lived in extreme isolation, the gene that produces Amelogenin-Y could have mutated or vanished entirely. In that scenario, some individuals could have been male — their teeth simply lacked the protein scientists normally use to detect them.

Either way, the results matter. If the chamber was deliberately female-only, it would point to surprisingly elaborate social customs, and possibly symbolic burial traditions once considered exclusive to modern humans.

Why this changes the study of human evolution

Dickinson noted the broader significance: "These findings offer rare insights into a culture that has, until now, been difficult to access directly. Advances in ancient protein analysis are opening the door to a far richer and more nuanced understanding of ancient hominins."

The study, listed under DOI 10.1016/j.cell.2026.05.044, carries 20 authors including Palesa P. Madupe, Marc R. Dickinson, John Hawks, Lee Berger and Enrico Cappellini.

Whether the fossils all belong to females, or to a mix that includes males with an unusual genetic signature, the discovery gives researchers a new lens on Homo naledi. Proteins locked in tooth enamel revealed something the bones alone never could.

As the investigation continues, the findings could reshape how scientists understand the social lives — and possibly the burial traditions — of ancient human species.