Dense tropical rainforests were long thought to be one of the last places where early humans could survive. For decades, researchers believed that our ancestors lived primarily in open grasslands and coastal areas, avoiding the dense forests of Africa until much later in history. Evidence from West Africa is now forcing scientists to dramatically reconsider that assumption.
Researchers investigating an archaeological site in present-day Côte d’Ivoire found evidence that humans lived in wet tropical forests about 150,000 years ago. The discovery pushes back the oldest known evidence of rainforest habitation by more than double previous estimates and suggests that early Homo sapiens were far more adaptable than previously thought.
Conclusion, published in NatureSupport the growing view that human evolution did not occur in a single environment. Instead, ancient populations appear to have thrived in a surprising range of ecosystems, from deserts and coastlines to dense forests.
Ancient stone tools hidden under the forest
The story started decades ago. In the 1980s, Professor Yode Guede of L’Université Félix Houphouët-Boigny helped investigate a site called Bête I during a joint Ivorian-Soviet research mission. Excavation has now revealed layers of stone tools buried under the ground in the rainforest area.
At the time, researchers couldn’t determine exactly 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 ago.
“With Professor Guede’s help, we relocated the original trench and were able to re-examine it using cutting-edge 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.
Timing turned out to be of the essence. Since the new excavations, mining activity has destroyed the site, making the recovered data particularly valuable.
Evidence of true rainforest environment
To determine the age of the site, scientists used several dating techniques, including optically stimulated luminescence and electron-spin resonance. Both methods pointed to human occupation around 150,000 years ago.
The researchers then analyzed chemical traces preserved in pollen, phytoliths (small silica structures left by plants) and sediment. The results showed that the area was heavily forested at the time humans lived there.
The samples included pollen and plant waxes associated with humid West African rainforests, while the very low levels of grass pollen suggest that the site was covered with dense forest rather than a thin strip of forest.
Before this discovery, the oldest preserved evidence of humans living in African rainforests only dated back to about 18,000 years ago. The previous global record of habitation in rainforests came from Southeast Asia and dates back to about 70,000 years ago.
“Prior to our study, the oldest secure evidence of habitation in African rainforests was about 18 thousand years ago and the oldest evidence of rainforest habitation anywhere came from south-east Asia about 70 thousand years ago,” said lead author Dr. Eslem Ben Aras. “This pushes the oldest known evidence of humans in the rainforest back more than twice as far as previously thought.”
Rethinking human development
The discovery adds to a growing body of evidence indicating that early humans were ecological generalists who were able to survive in many different habitats. Scientists increasingly believe that this flexibility may have helped homo sapiens Spread successfully around the world while other human relatives disappeared.
The subsequent discussions surrounding the research have also highlighted how difficult rainforest archeology can be. Fossils rarely survive in the hot, humid environment, and dense vegetation makes excavation challenging. Because of this, many scientists suspect that there are far more ancient rainforest sites across Africa still waiting to be found.
The study also raises larger questions about how long humans have influenced tropical ecosystems. Researchers are now exploring whether ancient populations may have shaped rainforest environments much earlier than previously thought through hunting, fire use, and plant management.
“The converging evidence shows without a doubt that ecological diversity is 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 areas and habitat types.”
Scientists believe that exploration of Côte d’Ivoire may be only the beginning. Several additional sites in the region remain largely unknown, raising the possibility that older evidence of humans living in the rainforest may still be uncovered.
The research was funded by the Max Planck Society and the Leakey Foundation.