Julia Chivu ’23

In the 1970s, archaeologists discovered a 15-piece fossil named KNM-ER 1500 in East Turkana, Kenya. Despite previous examinations, the classification of this fossil has not been determined,  due to severe weathering and fragmentation of the bones. Given the discovery location and morphological features, it has been suggested that KNM-ER 1500 could potentially belong to Paranthropus boisei, Homo habilis, Homo rudolfensis, or Homo erectus. Therefore, Dr. Carrie Mongle, along with a team of researchers from Stony Brook University’s Department of Anthropology, conducted an investigation into the taxonomy of this fossil. 

Despite the condition of the mandible (jaw bone), femur (thigh bone), and radius (a forearm bone), the researchers meticulously compared KNM-ER 1500’s bones to those of other early hominins. Additionally, surface scans were used to facilitate visualization of the morphology of the bones.

The researchers’ analysis suggests that the  KNM-ER 1500 fossil likely belongs to the P. boisei species. The mandible displays a widened corpus and blunt marginal crest, consistent with other P. boisei fossils. In addition, the absence of the intertoral sulcus, a particular groove present in many homo species, further suggests that this fossil originates from P. boisei. The shape of the femoral neck is crucial because it differentiates between hominin groups. For instance, the KNM-ER 1500 femur bone lacks a particular forward expansion in this region characteristic of Homo species. A distinctive ridge found along the lower back part of the femoral neck could be a unique characteristic linked to the East African Paranthropus. After inspecting the radius of this fossil, however, more morphological similarities associated with the Paranthropus and Australopithecis species than with Homo were identified. Additionally, the difference in the radial head diameter between the KNM-ER 1500 fossil and a previously-identified P. boisei specimen, the OH 80 fossil, suggests that there may be body size dimorphism within the P. boisei species. Moreover, the smaller size of the mandible of KNM-ER 1500 relative to the OH 80 mandible supports the idea that KNM-ER 1500 may have been a female. The analysis of rare postcranial fossils such as KNM-ER 1500 is crucial for improving our understanding of the anatomy of this species.

Works Cited: 

[1] C. Ward, et al., Taxonomic attribution of the KNM-ER 1500 partial skeleton from the Burgi Member of the Koobi Fora Formation, Kenya. Journal of Human Evolution 184, (2023). doi: 10.1016/j.jhevol.2023.103426. [2] Image retrieved from: https://commons.wikimedia.org/wiki/File:Em_-_Paranthropus_boisei_-_1.jpg