The oldest presence of our species found in a forest: 150,000 years ago in Ivory Coast

In the early 1980s, a scientific expedition from the Soviet Union and the Ivory Coast succeeded in a seemingly impossible mission. They found traces of humans in the middle of the rainforest: stone tools carved by Homo sapiens thousands of years ago. The technology of the time could not pinpoint the exact date. Years passed, the site of the excavations was forgotten, and the tools found were lost in 2011 during the second civil war that ravaged the Ivory Coast.

In 2020, another team led by one of the scientists who made the original discovery located and excavated the site again. The work has allowed them to accurately date the original location where the tools were found and determine that the oldest ones are 150,000 years old. This is an impressive find, because until now the oldest presence of our species in forested areas of Africa was just 18,000 years ago.

The new data challenge the classic theory of Homo sapiens evolution. This narrative holds that the first members of the species emerged about 300,000 years ago, probably in an open savannah landscape, as the oldest fossils have been found in these environments in East Africa. That original population spread across the rest of the continent and jumped into Asia and Europe. Until now, it was thought that tropical forests acted as a natural barrier and were excluded from that expansion until relatively recently.

“In recent years, thanks to new genetic and archaeological data, we have realized that this view is false, and our study is further proof of this,” explains to this newspaper the paleoanthropologist Eslem Ben Arous , researcher at the National Center for Human Evolution in Burgos, and first author of the study, which is published this Wednesday in Nature , a reference for the best world science.

A 32-year-old Parisian, Ben Arous is an expert in two new dating techniques for quartz crystals in sediments, which have been applied to the two layers of soil at the Ivorian site. The results show that one of them indicates continuous human presence from 150,000 years ago to 50,000 years ago. The most recent band indicates sapiens presence between 20,000 and 12,000 years ago. Analysis of pollen and other compounds shows that this area of ​​Ivory Coast was covered by rainforests.

Bea Arous explains: “For decades, research into the origin of our species in Africa has focused on areas with a high potential for fossil discovery: open environments such as grasslands and open savannahs , and coastal areas.” “These two environments are particularly important for understanding the dispersal of human populations within Africa and beyond. However, the overrepresentation of these regions has led to a dominant view that we have always been taught in our school textbooks: we expanded from a single origin,” she adds. Furthermore, it is virtually impossible for human fossils from tens of thousands of years ago to be preserved in these humid and warm terrains. Very few teams dare to excavate in the forest and that is why so little is known about human evolution in this environment.

The new discovery shows that our species inhabited the African wilderness for tens of thousands of years. It also shows that, as was logical to think, these were the first jungles in the world to be populated, although until now the oldest presence of sapiens in rainforests was in Asia, some 70,000 years ago. The main conclusion of the work is that our species does not have a single cradle, but that there was joint evolution of different groups in very different environments, including tropical forests, the authors of the discovery emphasize.

The original site, Bété 1, was located about 20 kilometres from the capital Abidjan, but was destroyed in 2022 by the opening of a mine. Despite this, Ivorian Yodé Guedé, a researcher at the Institute of History and Archaeology of Côte d'Ivoire, stresses: “This discovery is only the first of many that will be made, as there are more sites in the country's rainforests waiting to be studied.” Guedé was one of the leaders of the Soviet-Ivorian expedition in the 1980s, and one of the main authors of the current research, together with Eleanor Scerri , from the Max Planck Institute for Geoanthropology, in Germany.

CSIC paleoanthropologist Antonio Rosas , who was not involved in the study, believes that this finding supports the idea that Homo sapiens is a “pan-African” species. “The typical evolutionary image of our species taking one step after another is not correct,” he points out. In reality, there were many groups in different environments, some isolated, others in contact, which contributed different physical, cognitive and cultural traits to form the physiognomy and unique intellect of Homo sapiens , he points out. The “great contribution” of the new study in the Ivory Coast, Rosas adds, is that it has carried out a sophisticated analysis of ancient pollen and other biochemical compounds of plants that demonstrate beyond a doubt that this area was a rainforest 150,000 years ago.

Rosas highlights a paradox: we know more about the evolution of Neanderthals in Europe at this time than we do about our own species in Africa. But new campaigns in unexplored areas of the western part of the continent are opening a new window on the parallel evolution of sapiens and Neanderthals. Just over a month ago, Rosas announced the discovery of human tools from 40,000 years ago in Equatorial Guinea. The find, carried out in Río Campo , revealed that our ancestors not only survived, but thrived in one of the most challenging ecosystems on the planet, thanks to advanced stone technology and a remarkable capacity for social organisation. The tools of the African sapiens were very similar to those of contemporary Neanderthals. What is interesting is that the sapiens groups of the African forests “persisted for a long time”, until about 20,000 years ago or even less, Rosas highlights. Meanwhile, Neanderthals became extinct about 40,000 years ago, precisely when Homo sapiens arrived in Europe .