Abstract:
New ages for flowstone, sediments and fossil bones from the Dinaledi Chamber are
presented. We combined optically stimulated luminescence dating of sediments with U-Th and
palaeomagnetic analyses of flowstones to establish that all sediments containing Homo naledi
fossils can be allocated to a single stratigraphic entity (sub-unit 3b), interpreted to be deposited
between 236 ka and 414 ka. This result has been confirmed independently by dating three H.
naledi teeth with combined U-series and electron spin resonance (US-ESR) dating. Two dating
scenarios for the fossils were tested by varying the assumed levels of 222Rn loss in the encasing
sediments: a maximum age scenario provides an average age for the two least altered fossil teeth
of 253 +82/–70 ka, whilst a minimum age scenario yields an average age of 200 +70/–61 ka. We
consider the maximum age scenario to more closely reflect conditions in the cave, and therefore,
the true age of the fossils. By combining the US-ESR maximum age estimate obtained from the
teeth, with the U-Th age for the oldest flowstone overlying Homo naledi fossils, we have
constrained the depositional age of Homo naledi to a period between 236 ka and 335 ka. These
age results demonstrate that a morphologically primitive hominin, Homo naledi, survived into the
later parts of the Pleistocene in Africa, and indicate a much younger age for the Homo naledi fossils
than have previously been hypothesized based on their morphology.
