Alfonso Benito Calvo, a researcher at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) is part of an international team led by the Consejo Superior de Investigaciones Científicas (CSIC), which has just published a paper in the journal Nature on the Olduvai Gorge (Tanzania), which reveals that the production of bone tools 1.5 million years ago was methodical and systematized. 

This research is a milestone in the archaeology of human origins because before discovering this set of bone tools in the excavations of the T69 Complex site of Olduvai, it was thought that the manufacture of this type of instrument was practically unknown among our most remote ancestors. 

"This discovery suggests that the first humans significantly expanded their technological options, which until then were limited to the production of stone tools, and in turn, this indicates advances in the cognitive abilities and mental structures of these hominins (hominids with bipedal locomotion), who knew how to incorporate technical innovations, adapting their stoneworking techniques to working with bone remains," explains Ignacio De la Torre, CSIC researcher at the Instituto de Historia and co-director of the excavation.

CENIEH geologist Alfonso Benito Calvo was responsible for the geological analysis of the site, mapping and analyzing each layer of sediment, as well as applying various statistical studies to decipher the processes that led to the accumulation and preservation of such an abundant and spectacular archaeological site. 

“The site was formed on the eastern bank of Olduvai Paleo-Lake, where heavy rains caused a flood that inundated the lakeside plain. As the flood waters slowed down, they deposited their suspended sediment, burying the entire archaeological complex," says Alfonso Benito.

Stone tools, the key to an evolution

In East Africa, there is the oldest evidence of the use of tools by the first ancestors of the Homo genus. The most famous is the Oldowan culture, named after the artifacts found in the Olduvai Gorge. The Oldowans lived between 2.5 and 1.5 million years ago. This relatively simple technology gave rise about 1.7 million years ago to a new culture: the Acheulean (which lasted until 150,000 years ago). Until this discovery, the transition from the Oldowan to the Acheulean culture was known almost exclusively through stone artifacts.

"Our discovery indicates that, from the beginning of the Acheulean, the period in which the T69 Complex in the Olduvai Gorge was formed and in which it is evident that humans already had primary access to meat resources, animals were no longer only a source of danger, competition or proteins, but also a source of raw materials with which to make tools," says De la Torre.

The results of this study demonstrate that, during the transition from Oldowan to Acheulean technology, East African hominins developed a cultural innovation that involved the transfer and adaptation of carving skills from stone to bone. “By producing technologically and morphologically standardized bone tools, early Acheulean carvers developed technological repertoires that were previously thought to have appeared routinely more than 1 million years ago,” says De la Torre. "This innovation could have had a significant impact on the behavioral and adaptive potential of early humans, including improvements in their cognitive abilities, technological development and the acquisition of raw materials," he adds.

The OGAP Project

The Olduvai Gorge Archaeology Project (OGAP) is led by Ignacio de la Torre (researcher at the Instituto de Historia and head of the Laboratorio de Arqueología del Pleistoceno, CSIC) and Jackson Njau (Indiana University, USA), and has partners from several institutions in Spain, including CENIEH (in addition to UAB and ICREA) and other countries (United Kingdom, France, Germany, USA, Canada and Tanzania). 

Since 2010, OGAP has organized 19 excavation campaigns in Olduvai, many of them investigating the transition between the Oldowan and the Acheulean, a transition that is largely linked to the study of Homo habilis and its evolutionary successor, Homo erectus. Between 2015 and 2022, OGAP researchers dedicated a significant portion of their efforts to excavating the T69 Complex, discovering, restoring and analyzing the bone tools written about in Nature. 

The scale and intensity of OGAP's fieldwork have been made possible by two grants from the European Research Council awarded to De la Torre, ORACEAF (Starting Grants, 2012-2016) and BICAEHFID (Advanced Grants, 2019-2026); and, above all, thanks to the support of the Tanzanian authorities and local partners, especially the Maasai communities around Olduvai, who work closely with OGAP researchers in the discovery and study of the paleoanthropological treasures of the Olduvai Gorge, which is recognized as a UNESCO World Heritage Site.