When these results came out, there were a lot of quite nervous scientists.
A decade after their discovery in South Africa's Rising Star cave, the fossils of Homo naledi have delivered a new mystery: every individual whose biological sex could be determined through ancient tooth enamel proteins turned out to be female. Twenty specimens, zero males — a result so unexpected it unsettled the scientists who found it. Whether this reflects a deliberate, gender-based burial practice by a small-brained hominin, a natural demographic pattern, or a fundamental shift in the species' own genetic signature, the finding quietly reopens some of the oldest questions we carry about what it means to be human.
- Ancient protein analysis of 20 Homo naledi specimens produced a result no one anticipated: not a single male marker was found among them.
- The discovery has left paleontologists genuinely unnerved, forcing a reckoning with assumptions about this species' biology, social structure, and cognitive capacity.
- One provocative interpretation holds that Homo naledi deliberately buried the sexes separately — a form of ritual behavior that would challenge the idea that symbolic thinking belongs only to large-brained hominins.
- A competing explanation suggests the male genetic marker itself may have evolved away in this species, raising entirely different questions about Homo naledi's biology.
- Skeptics caution that small-brained hominins may simply have foraged in sex-skewed groups, and that demographic accident — not ceremony — could explain the cave's all-female population.
- Research now turns toward finding male remains elsewhere in the cave system and determining whether the genetic marker truly shifted over time.
In 2015, explorers in South Africa's Rising Star cave uncovered fossils of Homo naledi, a small-brained hominin whose place in human evolution has never quite settled. A decade on, a new analysis of those bones has produced something stranger still: every specimen that could be reliably tested was female.
The method was elegant — ancient proteins preserved in tooth enamel, examined for a genetic marker found only in males. Molecular scientist Palesa Madupe led the analysis of 23 specimens at Copenhagen's Globe Institute. After accounting for failed samples and duplicates, 20 distinct individuals remained. In every case, the male marker was absent. Twenty females. Zero males.
Paleoanthropologist Lee Berger, who directs the Rising Star excavations, described the scientific community as deeply nervous upon hearing the results. The finding demands explanation. One possibility: Homo naledi practiced sex-based burial rituals, separating the dead by gender — a behavior that would imply symbolic thinking and social organization in a creature long underestimated. Senior author Enrico Cappellini called both leading interpretations "fascinating" and freighted with deep implications.
The second explanation is equally striking: the male genetic marker may have changed or disappeared over evolutionary time in this species, pointing not to ritual but to biology.
Not everyone is persuaded by the burial hypothesis. Michael Petraglia of Griffith University praised the rigor of the research but urged caution, noting that small-brained hominins — much like non-human primates today — might naturally form groups with uneven sex ratios. A female-heavy foraging pattern, he suggested, could explain the cave's demographics without invoking ceremony.
The Rising Star cave continues to resist easy answers. Whether those twenty female skeletons represent a gendered burial ground, a natural clustering, or something else entirely, the next phase of research will look for male remains elsewhere in the system — and listen carefully to what the fossils have yet to say.
In 2015, explorers working in South Africa's Rising Star cave system uncovered fossils of a species called Homo naledi—a small-brained hominin whose place in human evolution has puzzled researchers ever since. Now, a decade later, a new analysis of those bones has produced a finding so unexpected that it left the scientific community genuinely unsettled. Every single specimen that researchers could reliably test turned out to be female.
The discovery emerged from an ingenious method: scientists extracted ancient proteins preserved in tooth enamel and used them to identify biological sex. Palesa Madupe, a molecular scientist at Copenhagen's Globe Institute, led the analysis of 23 specimens. Two samples failed to produce usable results, and two came from the same individual, leaving 20 distinct individuals in the final dataset. The team looked for a specific genetic marker found only in males. In all twenty cases, that marker was absent. Twenty females. Zero males.
Lee Berger, the paleoanthropologist who directs the ongoing excavations at Rising Star and serves as National Geographic's explorer-in-residence, described the moment the results arrived: the scientific community was, by his account, deeply nervous. This was not what anyone had anticipated. The finding forces a reckoning with basic assumptions about Homo naledi's biology and social life. If the cave truly held only females, something unusual was happening there—something that demands explanation.
One possibility is that Homo naledi practiced sex-based burial rituals. Berger has suggested that the species may have deliberately separated the dead by sex and gender, treating male and female remains according to different ceremonial practices. This interpretation aligns with earlier arguments that Homo naledi engaged in intentional burial at all—a behavior long considered uniquely human. If true, it would suggest a level of symbolic thinking and social organization that challenges how we understand a creature with such a small brain.
But there is another explanation, equally striking. The male genetic marker itself may have changed or been deleted over evolutionary time in this species. Enrico Cappellini, a senior author of the study and a paleoproteomics professor at Copenhagen's Globe Institute, acknowledged both possibilities as "fascinating" and carrying "deep implications" for understanding Homo naledi's biology and history. Either scenario—ritualized sex-based burial or a fundamental shift in the male genetic signature—would represent a remarkable discovery.
Not everyone is ready to embrace the burial interpretation. Michael Petraglia, a professor at Griffith University and director of an Australian research center focused on human origins, urged caution. While he praised the researchers' scientific rigor, he pushed back on the leap from "all female" to "intentional sex-based burial." Petraglia pointed out that small-brained hominins, much like non-human primates today, might naturally form groups with skewed sex ratios. If Homo naledi foraged in particular locations on the landscape, those locations might simply have attracted more females than males—a demographic pattern that would require no ritual explanation at all.
The tension between these interpretations reflects a deeper challenge in paleontology: the same evidence can support multiple stories. What is certain is that the Rising Star cave system continues to yield surprises. Whether those twenty female skeletons represent a deliberate burial ground organized by gender, a natural clustering of foraging behavior, or something else entirely, remains an open question. The next phase of research will likely focus on whether male remains exist elsewhere in the cave system, whether the genetic marker truly changed over time, and what other clues the fossils themselves might hold.
Notable Quotes
When these results came out, there were a lot of quite nervous scientists. This was not what we expected.— Lee Berger, paleoanthropologist leading Rising Star excavations
It is entirely possible that Homo naledi, being a small-brained hominin, and similar to non-human primates, had groups with high female to male sex ratios, foraging in particular places on the landscape.— Michael Petraglia, Griffith University professor
The Hearth Conversation Another angle on the story
Why would every single specimen be female? That seems statistically impossible by chance.
It does seem extreme. That's why researchers are considering two very different explanations—either Homo naledi was deliberately placing only females in this particular spot, or the male genetic marker itself evolved differently in this species over time.
And which explanation do you find more convincing?
Honestly, both are fascinating but unproven. The burial ritual idea is seductive because it suggests symbolic thinking. But Petraglia's point is worth taking seriously—small primate groups do naturally develop uneven sex ratios depending on where they forage.
So we're back to not knowing.
We're back to having better questions. The fact that we can now test ancient proteins at all is remarkable. Ten years ago, this finding would have been impossible.
What happens next?
They'll keep digging in that cave system. If they find male remains elsewhere, that changes the story. If they find more females in the same spot, the ritual explanation gains weight. And they'll keep testing the genetic marker itself to see if it really did shift over time.