A reassessment of a fossilised tooth provides the first strong piece of evidence for the presence of early hominins (humans and their ancestors) in the Western Rift Valley in Central Africa nearly 2 million years ago.
The East African Rift system which runs southward through eastern Africa actually consists of two main branches: the main eastern Gregory Rift and the smaller western Albertine Rift. The eastern section, along with several locations in southern Africa, is regarded as the cradle of human evolution and contains sites where hundreds of early hominin fossils have been unearthed since the 1960s. Although part of the same system, no such discoveries have yet been made in the western Albertine branch of the Rift.
Some tantalising clues do exist, however. Simple artefacts have been discovered which indicate that hominins were present in the Western Rift Valley around 2 million years ago. And it is known that the Albertine branch underwent several climatic changes 3-2 million years ago which resulted in the appearance of plants and animals that were adapted to more open grassland conditions, similar to those found on the eastern rift. Yet, actual fossil evidence from this region remains scarce.
Recently, however, an old archaeological collection from the Department of Anthropology and Prehistory in the Royal Belgian Institute of Natural Sciences (RBINS) was reassessed. This included samples originally excavated by the Belgian geologist Jean de Heinzelin from the Ishango archaeological site in the Democratic Republic of Congo in the 1950s. While most of the collection contained items dating from the Late Stone Age, researchers also rediscovered a large isolated tooth amidst the artefacts.
This tooth, an upper molar from a young individual, had originally been found separate from the other fossils in a layer of sediment dating back to the Plio-Pleistocence, approximately 2.6-1.8 million years ago. Thrillingly, further analysis revealed that the tooth was unlike that of a modern human and instead contained features similar to those of early hominins (particularly australopiths and early Homo) from East and southern Africa.
This is an exciting rediscovery and makes this tooth the first compelling piece of evidence for the occupation of Central Africa by early hominins nearly 2 million years ago. It adds to our understanding of early hominin evolution and suggests that they were able to disperse to new regions beyond East and southern Africa once the environment shifted to more suitable open grassland conditions. This study also highlights the tremendous knowledge than can be gleaned when old samples are reanalysed using modern techniques.
Reference: Isabelle Crevecoeur, Matthew M. Skinner, Shara E. Bailey, Philipp Gunz, Silvia Bortoluzzi, Alison S. Brooks, Christian Burlet, Els Cornelissen, Nora De Clerck, Bruno Maureille, Patrick Semal, Yves Vanbrabant, & Bernard Wood (2014). First Early Hominin from Central Africa (Ishango, Democratic Republic of Congo) PLoS ONE, 9 (1) DOI: 10.1371/journal.pone.0084652
Image: Crevecoeur et al. (2014)