An investigation into the age of one of the oldest Homo erectus fossils led to the discovery of new bones

The Homo erectus fossil cataloged as KNM-ER 2598
An article published in the journal “Nature Communications” reports a research on a fossil bone attributed to a Homo erectus that led to the discovery of two other fossils in the same area, near the east shore of Lake Turkana, Kenya. A team of researchers led by Ashley Hammond, assistant curator in the American Museum of Natural History’s Division of Anthropology, conducted an investigation to try to understand whether that skull bone really was the oldest fossil of Homo erectus or, as some suspected, it came from a more recent layer and got moved by water or wind. The survey supports the age attributed to the fossil of nearly 1.9 million years.

The occipital bone of a skull attributed to a Homo erectus was found in 1974 and cataloged as KNM-ER 2598. The image (courtesy Hammond, A.S., Mavuso, S.S., Biernat, M. et al. All rights reserved) illustrates the position of the bone in the skull and offers a posterior and a side view. Dating to nearly 1.9 million years made it the oldest fossil attributed to this species, predating most other fossils attributed to the same species by a few hundred thousand years.

The discussion about the KNM-ER 2598 fossil started because that bone was discovered on the surface, not excavated in a place where sediments and other elements could help in its dating. This left the suspicion that it had come from a more recent sedimentary layer. Ashley Hammond’s team tried to piece together the story of that fossil’s discovery with an investigation of which she herself published the story. The results support the original dating.

An unexpected but certainly welcome result of this research came from the discovery, within 50 meters of the site where the KNM-ER 2598 fossil was discovered, of a partial pelvis and foot bone belonging to ancient hominins. All those bones may have belonged to the same individual but it wasn’t been possible to establish that. Five small bone fragments that were probably part of a skull were also discovered, but none of them fits into KNM-ER 2598.

Fossils of other vertebrates, especially mammals, were discovered in the same area and offer information on the environment in which Homo erectus lived. The analyzes carried out suggest that the environment was rather arid but could still support the life of herbivorous species.

This study shows how even a few fragmentary fossils can help to better understand some characteristics of an environment of almost two million years ago. Homo erectus was a successful species with the ability to build tools and spread to different environments, so understanding its history better helps to understand where modern humans come from.

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