Every Homo naledi Fossil in the Rising Star Cave Is Female: Two Leading Theories Why

This finding has forced a re-evaluation of the site. It also raises a fundamental question: why were only females deposited in this cave?

The Two Leading Interpretations

Scientists have proposed two main hypotheses to explain the all-female assemblage .

1. Intentional Sex-Selective Burial (Cultural Practice)

The more provocative interpretation is that Homo naledi practiced deliberate, sex-selective burial or mortuary caching — meaning only females were interred in the Dinaledi and associated chambers, while males were disposed of elsewhere . If true, this would represent the oldest known example of sex-specific funerary behavior in the hominin fossil record, implying a complex social structure with strong cultural segregation by sex .

"Our interpretation is that they had some kind of cultural practice," said Professor John Hawks, a co-author of the paper and member of the Rising Star team . This hypothesis builds on previous evidence that H. naledi deliberately placed its dead in the deep chambers — evidence that remains controversial .

2. Sampling or Biological Bias (Non-Cultural Explanation)

The null hypothesis is that the all-female signal reflects something other than intentional cultural practice:

• Sampling bias: A catastrophic event or natural trap could have selectively affected only females — perhaps a female band or nursery group. The cave may have preserved only a specific subgroup .

• Biological absence of Y-chromosome protein: It is possible that Homo naledi males simply did not produce the AMELY protein in their enamel, or that the protein degraded differently over time, making the test unable to detect males even if they were present . However, the researchers note that the AMELX protein was well-preserved and detectable, which makes a uniform preservation failure of AMELY alone seem less likely .

A 2024 study had already flagged the possibility of sex-biased sampling in the H. naledi dental sample, finding that variation at four tooth positions was "so low that the possibility that one sex is represented by few or no individuals in the sample cannot be excluded" .

What Makes This Finding So Significant

The all-female result is not the only surprise. The fact that ancient proteins could be extracted at all from 200,000- to 335,000-year-old teeth in a subtropical cave is a methodological breakthrough . The technique opens a new window into studying the biology of extinct hominins where DNA is not preserved.

Moreover, the finding strengthens the case for deliberate burial. Natural processes rarely produce such a uniform demographic profile. "Finding a massive trove of ancient bones from only one sex is almost unheard of in paleoanthropology," noted National Geographic . That the assemblage includes infants and children — individuals who could not have entered the cave on their own — further supports the idea that others placed them there .

What the Researchers Say

Paleoanthropologist John Hawks described the finding succinctly: "The most fascinating result is the simplest: none show any signs of male markers" . But he and other researchers emphasize that both interpretations remain on the table pending further fossil discoveries from other sites .

The team plans to apply the protein analysis technique to other Homo naledi sites and to other hominin species to see if the all-female pattern is unique to Rising Star or a more widespread phenomenon.

For now, the mystery remains: a cave full of females, and no males in sight. Whether this is the result of culture, catastrophe, or a quirk of protein preservation is one of the most compelling open questions in paleoanthropology today.