A new study published in the journal Nature reveals that humans were living in African rainforests at least 150,000 years ago, earlier than previously believed. The discovery pushes back the known evidence of human habitation in rainforests by over 80,000 years.
The research team found that humans were living in rainforests within present-day Côte d'Ivoire, uncovering a clear association between late Middle Pleistocene material culture and wet tropical forests in the region. The Bété I site, first excavated in 1982 by Professor Yodé Guédé of the Université Félix Houphouët-Boigny, yielded ancient stone tools demonstrating this deep-time association.
“The oldest evidence of rainforest habitation worldwide was found in Southeast Asia and dates to about 70,000 years ago. Our discovery pushes the oldest known evidence of human presence in rainforests back more than twice as far,” said Dr. Eslem Ben Arous, lead author of the study from the National Centre for Human Evolution Research (CENIEH) in Spain, according to 20 Minutos.
The study argues that human evolution occurred in several regions and habitats, reflecting a complex history of population subdivision, confirming the predictions of the pan-African model of human evolution. "This work reflects a complex history of population subdivision, in which different populations lived in different regions and habitat types," said Professor Eleanor Scerri, head of the Human Paleosystems research group at the Max Planck Institute of Geoanthropology, according to Scientias.
These findings challenge previous assumptions that rainforests were unimportant habitats for early humans.
"Humans had to deal with poisonous snakes, avoid large cats, and recognize poisonous plants," said Scerri, according to Tagesschau.
The Bété I site today lies within a dense grove of rainforest, presenting challenges such as heavy rain and poor visibility. At the time of the original excavation, the age of the tools revealed from the deep layers could not be determined, and it was unknown what the ecological environment was at the time of their use.
Professor Mark Bateman from the University of Sheffield used a dating technique known as optically stimulated luminescence to discover the burial age of individual grains of sand from eight samples across the site. "Key to finding when they were being used was the application of modern dating techniques to the sediments in which the stone tools were found," added Professor Bateman.
Analyses indicated that when humans were dropping their stone tools in the region, it was a heavily wooded wet forest, typical of humid West African rainforests. Ancient pollen, silicified plant remains known as phytoliths, and leaf wax isotopes from site sediments confirmed this environment. The area had abundant forest with a consistent presence of pollen types typical of wet-humid West African rainforests, riparian forests, and swamp forests.
"The sedimentary, biomarker, and microfossil results are remarkably consistent, showing evidence for alluvial deposition in a tropical forest environment consisting of riparian, swamp, and rainforest taxa," noted the study in Nature.
These findings suggest that West Africa may have been an important center in the early evolution of modern humans, as some early modern humans lived in rainforests while others remained in grassland and savannah habitats. Scerri stated, "We now need to ask how these early human niche expansions impacted the plants and animals that shared the same niche space with humans," according to Newsweek.
The Bété I site was destroyed between 2020 and 2021 by quarrying activities, making the collected samples crucial for understanding early human life in the rainforest. "This study was completed just before the site was destroyed by mining activity, highlighting that being able to do work such as this is vitally important in being able to further study the history and evolution of the human species," said Professor Bateman.
The research highlights the need for further exploration in West Africa, a region that remains under-researched compared to other parts of the continent. Its archaeological sequence and specific regional characteristics are yet to be fully understood. "Convergent evidence undoubtedly shows that ecological diversity is deeply rooted in our species," said Ben Arous, according to Scientias.
The research team argues that rainforests have long been overlooked as a setting for human development, despite representing a major world biome. Rainforests were thought to be natural barriers to human occupation, contributing to the belief that humans did not inhabit these environments until relatively recently.
"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," said Guédé, according to Newsweek.
The article was written with the assistance of a news analysis system.