A study of two new skulls of Homo erectus up to 1.5 million-years-old

Catalan Institute of Human Palaeoecology and Social Evolution (IPHES)
  • New Homo erectus skulls were found at Gona, in the Afar Triangle of Ethiopia, close to the area where the notoriousAustralopitecus afarensis hominin “Lucy” was discovered in 1974
  • Researcher Isabel Cáceres analyzed the fossil remains found next to the skulls and confirmed mammal exploitation by these hominins
  • The association of Oldowan and Acheulian tools with these crania endorses a cultural and behavioral complexity of this species that has yet to be fully understood

 

The discovery of two new skulls of Homo erectus

Homo erectus is one of the extinct species of archaic humans living in the Pleistocene (as early as 2 million years ago), and the first human acestor to spread from Africa into Europe and Asia.  It is one of the earliest species that can be clearly into the Homo genus.

The discovery of two new skulls of Homo erectus found at Gona (Ethiopia) was published in the Science Advances journal by an international team. The effort was led by Sileshi Semaw, researcher at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) in Burgos, and Michael Rogers at Southern Connecticut State University (SCSU), USA, and in which Dr. Isabel Caceres, researcher from the Universitat Rovira i Virgili (URV) and the Catalan Institute of Human Paleoecology and Social Evolution (IPHES), in Tarragona, participates since 2013.

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DAN5 cranium, the smallest skull of Homo erectus recovered in Africa. Photo: Michael J. Rogers/SCSU.

Gona is located in the Afar Triangle, located beside the well-known study areas of Middle Awash and Hadar, where the famous skeletons “Ardi” and “Lucy” were found, respectively. One of the newfound skulls is a nearly-complete hominin cranium estimated to ~1.5 million years (Ma) ago and was discovered at the site of Dana Aoule North (DAN5). The other one is a partial cranium dated to ~1.26 Ma ago and was recovered from the Busidima North site (BSN12).

DAN5 cranium has the smallest endocranial volume documented for H. erectus in Africa, about 590 cubic centimeters. This is a gracile skull that bears some similarities with the small individuals discovered at Dmanisi (Georgia). For its part, the BSN12 partial cranium is robust and large (800-900 cc.), similar to OH9 individual from Olduvai Gorge. The small size of the DAN5 cranium suggests that it could belong to a female individual and that H. erectus hence was probably a sexually dimorphic species.

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Map of the Gona study area showing locations of BSN12 and DAN5.

 

Clues on Homo erectus culture

Both crania were associated with simple Oldowan-type (Mode 1) and more complex Acheulian (Mode 2) stone tool assemblages. Thus, instead of finding only the expected large handaxes or picks (tools typically associated with H. erectus), the Gona team found both elaborated, well-made handaxes and plenty of less-complex Oldowan tools and cores. This suggests that Homo erectus had a degree of cultural/behavioral plasticity that is yet to be fully understood.

The hominins at both sites lived close to ancient rivers, in an environment with riverine woodlands adjacent to open habitats. The low δ13C isotope value from the DAN5 cranium (from the right molar) is consistent with a diet dominated by C3 plants (trees and shrubs, and/or animals that ate these plants) or, alternatively, by broad spectrum omnivore.

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Cutmark on a medium-sized long bone from DAN5 related to defleshing activities.

Isabel Cáceres studied the taphonomy (the transition of biological matterto become part of the lithosphere) of the faunal remains from the deposits where the two skulls were found. That is, the study of bone surface modifications the fossils present was analyzed. While in BSN12 no anthropic evidences were identified, in DAN5 the use of stone tools was evident in defleshing and marrow consumption activities in animals of different size. This implies that H. erectus butchered large, medium and small mammals, although it has not been established whether these were obtained by hunting.

In conclusion, DAN5 and BSN12 sites at Gona are among the earliest examples of H. erectus associated with Oldowan and Acheulian stone tool assemblages. The investigations carried out at Gona have clearly shown that Oldowan technology persisted much longer after the invention of the Acheulian. This is an indicative of a particular behavioral flexibility and cultural complexity of H. erectus.

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Isabel Cáceres during fieldwork at the Gona excavation sites.

 

 

Image credits:

Images used were kindly provided by IPHES and re-used with permission. Pictures by Michael J. Rogers, SCSU indicated in picture captions.

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