Dating of Broken Hill skull leads to questions over modern human ancestry

Scientists from the Natural History Museum have helped date the Broken Hill skull, a key early human discovered in Africa in the 1920s. The study led by Professor Rainer Grün at the Griffith University, Australia, estimates that the skull is between 274,000 and 324,000 years old, which is much younger than previously thought.

Discovered in 1921 by miners in Zambia, the Broken Hill skull is one of the best-preserved fossils of the early human species Homo heidelbergensis and was estimated to be about 500,000 years old. The fossil was donated to the Natural History Museum in the 1920s and is currently on display in the Museum's Human Evolution gallery.

Due to the chance discovery of the remains and the subsequent destruction of the original site by mining, historically it has been very difficult to determine the age of the skull. The research team used radiometric dating methods on the skull itself and material recovered near the cranium, as well as other finds from the site. The researchers also used sediment scraped directly off the skull in the 1920s, which was recently discovered in the collections of the Natural History Museum.

The Natural History Museum's Professor Chris Stringer said: "Through years of painstaking work including direct dating of the skull itself and other materials found around the Broken Hill site, I, geochronologist Rainer Grün, and other colleagues have produced a best age estimate of about 299,000 years for the Broken Hill skull. This is surprisingly young, as a fossil at about 300,000 years would be expected to show intermediate features between H. heidelbergensis and H. sapiens, but Broken Hill shows no significant features of our species".

The research also suggests that human evolution in Africa around 300,000 years ago was a much more complex process, with the co-existence of different human lineages.

Professor Stringer continues: “Previously, the Broken Hill skull was viewed as part of a gradual and widespread evolutionary sequence in Africa from archaic humans to modern humans. But now it looks as if the primitive species Homo naledi survived in southern Africa, H. heidelbergensis was in south-central Africa, and early forms of our species existed in regions like Morocco and Ethiopia”.

The paper is published in Nature on 1 April 2020.

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