Dense tropical rainforests were long considered some of the last places early humans could survive. For decades, researchers believed our ancestors mainly stuck to open grasslands and coastal regions, avoiding the thick forests of Africa until much later in history. Evidence from West Africa is now forcing scientists to rethink that assumption in a dramatic way.
Researchers investigating an archaeological site in present-day Côte d’Ivoire found evidence that humans were living in wet tropical forests roughly 150,000 years ago. The discovery pushes back the oldest known evidence of rainforest habitation by more than double previous estimates and suggests early Homo sapiens were far more adaptable than once believed.
The findings, published in Nature, support a growing view that human evolution did not happen in one single environment. Instead, ancient populations appear to have thrived across a surprising range of ecosystems, from deserts and coastlines to dense forests.
Ancient Stone Tools Hidden Beneath the Forest
The story began decades ago. In the 1980s, Professor Yodé Guédé of l’Université Félix Houphouët-Boigny helped investigate a site known as Bété I during a joint Ivorian-Soviet research mission. Excavations uncovered layers of stone tools buried deep underground in what is now rainforest territory.
At the time, researchers could not accurately determine how old the tools were or what the environment looked like when ancient humans lived there. That changed when an international team returned to the site using modern technology unavailable to scientists forty years earlier.
“With Professor Guédé’s help, we relocated the original trench and were able to re-investigate it using state of the art methods that were not available thirty to forty years ago,” said Dr. James Blinkhorn of the University of Liverpool and the Max Planck Institute of Geoanthropology.
The timing turned out to be critical. Since the new excavation, mining activity has destroyed the site, making the recovered data especially valuable.
Evidence of a True Rainforest Environment
To determine the age of the site, scientists used multiple dating techniques, including Optically Stimulated Luminescence and Electron-Spin Resonance. Both methods pointed to human occupation around 150,000 years ago.
Researchers then analyzed pollen, phytoliths (tiny silica structures left behind by plants), and chemical traces preserved in sediments. The results showed the area was heavily forested at the time humans lived there.
The samples contained pollen and plant waxes associated with humid West African rainforests, while very low levels of grass pollen suggested the site was surrounded by dense woodland rather than a thin strip of forest.
Before this discovery, the oldest secure evidence of humans living in African rainforests dated to only about 18,000 years ago. The previous global record for rainforest habitation came from Southeast Asia and dated to around 70,000 years ago.
“Before our study, the oldest secure evidence for habitation in African rainforests was around 18 thousand years ago and the oldest evidence of rainforest habitation anywhere came from southeast Asia at about 70 thousand years ago,” explained lead author Dr. Eslem Ben Arous. “This pushes back the oldest known evidence of humans in rainforests by more than double the previously known estimate.”
Rethinking Human Evolution
The discovery adds to a growing body of evidence showing that early humans were ecological generalists capable of surviving in many different habitats. Scientists increasingly believe that this flexibility may have helped Homo sapiens spread successfully across the world while other human relatives disappeared.
Follow-up discussions surrounding the research have also highlighted how difficult rainforest archaeology can be. Fossils rarely survive in hot, humid environments, and dense vegetation makes excavations challenging. Because of this, many scientists suspect there could be far older rainforest sites still waiting to be found across Africa.
The study also raises bigger questions about how long humans have influenced tropical ecosystems. Researchers are now exploring whether ancient populations may have shaped rainforest environments far earlier than previously assumed through hunting, fire use, and plant management.
“Convergent evidence shows beyond doubt that ecological diversity sits at the heart of our species,” said Professor Eleanor Scerri, senior author of the study. “This reflects a complex history of population subdivision, in which different populations lived in different regions and habitat types.”
Scientists believe the Côte d’Ivoire discovery may only be the beginning. Several additional sites in the region remain largely unexplored, raising the possibility that even older evidence of rainforest-dwelling humans could still be uncovered.
The research was funded by the Max Planck Society and the Leakey Foundation.