All Known Homo Naledi Are Female, With Fascinating Implications
▼ Summary
– All 20+ Homo naledi skeletons found in Rising Star Cave are genetically female, based on protein analysis of dental enamel.
– The teeth samples contained the female-specific protein AMELX but none contained the male version AMELY.
– The probability of this all-female result occurring by chance is 0.0000954 percent, suggesting intentional selection.
– The skeletons date to between 335,000 and 236,000 years ago and were found across four chambers in the cave system.
– The finding supports the theory that Homo naledi deliberately placed their dead in the cave, rather than accidental accumulation.
A groundbreaking analysis of Homo naledi remains from South Africa’s Rising Star Cave System has revealed that every known skeleton of this ancient human relative is female , and researchers believe this was no random occurrence.
Discovered in 2013 by a team led by anthropologist Lee Berger, the fossils of more than 20 small-bodied hominins were found deep within the cave system, dating back between 335,000 and 236,000 years. Since their unearthing, scientists have debated whether these individuals perished in a tragic accident or were intentionally placed there by their own kind. Now, a new clue from dental proteins may tip the scales toward the latter theory.
Molecular scientist Palesa Madupe of the Max Planck Institute for Evolutionary Anthropology and her team examined the dental enamel proteins from 23 teeth found across four separate chambers of the cave. These teeth belonged to at least 20 distinct individuals, ranging from infants to older adults whose teeth showed decades of wear.
Every single tooth sample contained amelogenin-X (AMELX), a protein linked to the X chromosome. None contained the male counterpart, AMELY, which is tied to the Y chromosome. In genetically male humans, dental enamel typically holds about one-tenth as much AMELY as AMELX. Given the levels of AMELX detected, the researchers say they would have spotted AMELY if it existed. But it did not.
The result: every known Homo naledi skeleton with teeth preserved , essentially the entire known population of the species , appears to be female. The statistical probability of this happening by chance is roughly the same as flipping a coin 20 times and landing on heads each time: a mere 0.0000954 percent. As Madupe and her colleagues see it, the metaphorical coin was weighted , likely by deliberate behavior, such as intentionally placing female bodies in the dark, winding passages of Rising Star.
This finding adds a compelling new layer to the ongoing mystery of Homo naledi and their burial practices, suggesting that gender selection may have played a role in how these ancient hominins treated their dead.
(Source: Ars Technica)
