While our species emerged in Africa approximately 300,000 years ago, the ecological settings that shaped early human development remain a subject of debate. Rainforests, often perceived as barriers to human expansion, have not been widely studied in this context. However, new findings indicate that humans had already established themselves in these environments much earlier than previously recognized.
The origins of this discovery date back to the 1980s when Professor Yode Guede of l'Universite Felix Houphouet-Boigny first examined the site as part of a collaborative Ivorian-Soviet expedition. The initial excavations uncovered deeply buried stone tools, suggesting ancient human activity. However, due to technological limitations at the time, neither the precise age of these artifacts nor the ecological conditions of their deposition could be determined.
"Several recent climate models suggested the area could have been a rainforest refuge in the past as well, even during dry periods of forest fragmentation," explains Professor Eleanor Scerri, leader of the Human Palaeosystems research group at the Max Planck Institute of Geoanthropology and senior author of the study. "We knew the site presented the best possible chance for us to find out how far back into the past rainforest habitation extended."
Determined to uncover more information, the Human Palaeosystems team revisited the site with advanced archaeological and dating techniques. "With Professor Guede'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," says Dr. James Blinkhorn, researcher at the University of Liverpool and the Max Planck Institute of Geoanthropology. The excavation came just in time, as the site has since been destroyed due to mining activities.
Prior to this study, the earliest securely dated evidence of human habitation in African rainforests was from around 18,000 years ago, with the oldest known global evidence coming from Southeast Asia approximately 70,000 years ago. "This pushes back the oldest known evidence of humans in rainforests by more than double the previously known estimate," states Dr. Eslem Ben Arous, researcher at the National Centre for Human Evolution Research (CENIEH), the Max Planck Institute of Geoanthropology, and lead author of the study.
To establish the age of the artifacts, researchers applied Optically Stimulated Luminescence and Electron-Spin Resonance dating techniques, determining a timeline of roughly 150,000 years ago. Further analysis of sediment samples for pollen, phytoliths (silicified plant remains), and leaf wax isotopes confirmed that the region was a dense rainforest during that time. Low levels of grass pollen indicated that the site was not a small patch of forest but part of an expansive and humid West African rainforest.
"This exciting discovery is the first of a long list as there are other Ivorian sites waiting to be investigated to study the human presence associated with rainforest," says Professor Guede joyfully.
"Convergent evidence shows beyond doubt that ecological diversity sits at the heart of our species," notes Professor Scerri. "This reflects a complex history of population subdivision, in which different populations lived in different regions and habitat types. We now need to ask how these early human niche expansions impacted the plants and animals that shared the same niche-space with humans. In other words, how far back does human alteration of pristine natural habitats go?"
Research Report:Humans in Africa's wet tropical forests 150 thousand years ago
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Max Planck Institute of Geoanthropology
All About Human Beings and How We Got To Be Here
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