Lost for 150,000 Years: Côte d'Ivoire Site Pushes Back Earliest Human Rainforest Habitation by More Than Double

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A reexamination of stone tools from Bété I in southwestern Côte d'Ivoire, published in Nature and amplified by ScienceDaily on May 19, 2026, has pushed back the oldest confirmed evidence of human life inside an African rainforest to 150,000 years ago. That is more than twice the previous record, and it forces archaeologists to rethink how and where the Homo sapiens lineage spread across the continent.

The original Bété I excavations were conducted in the 1980s and 1990s, but the site was largely lost to view after political instability and the closure of a quarry that had exposed its sediments. A team led by Dr. Eslem Ben Arous reopened the archives and combined two independent dating techniques, optically stimulated luminescence (OSL) and electron spin resonance (ESR), to reanchor the artifact-bearing layer in absolute time. Pollen and phytolith samples preserved alongside the tools confirmed that the environment at the time was a wet, closed-canopy tropical forest rather than an open savanna.

For decades the prevailing view, sometimes called the 'savanna hypothesis,' held that early Homo sapiens evolved on grasslands and only later, perhaps as recently as 70,000 years ago, learned to exploit dense rainforests. Tropical rainforests were considered green deserts: rich in plant matter but poor in the large game and accessible water that other ecosystems offered. Bété I directly contradicts that narrative.

The implications stretch beyond ecology. If our ancestors were capable of sustaining themselves in West African rainforests by at least 150,000 years ago, then the modern human capacity for behavioral flexibility, niche construction, and the development of specialized toolkits emerged earlier than many models assumed. It also suggests that the African archaeological record, long sampled most intensively in eastern and southern rift valleys, may seriously undercount populations that lived in the comparatively understudied tropical west.

reexamination: A new study or review of something previously analyzed.

lineage: A line of descent from an ancestor.

excavation: The careful digging of a site to study its history.

luminescence: The emission of light by a substance, used here as a dating method.

canopy: The upper layer of leaves and branches in a forest.

savanna: A grassy plain with scattered trees in tropical regions.

ecosystem: A community of living things and their environment.

specialized: Designed or developed for a particular purpose.

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A reappraisal of Bété I, a Stone Age locality in southwestern Côte d'Ivoire originally excavated in the 1980s and 1990s by Yodé Guédé but largely abandoned in subsequent decades, has yielded what the authors call the earliest unambiguous evidence of human occupation in an African rainforest. The work, published in Nature and amplified by ScienceDaily on May 19, 2026, was led by Eslem Ben Arous of the Spanish CENIEH together with collaborators from the Max Planck Institute for Geoanthropology and the Université Félix Houphouët-Boigny. Pairing optically stimulated luminescence on quartz grains with electron spin resonance on bleached sediment, the team places the artifact-bearing horizon at roughly 150,000 calibrated years before present, more than doubling prior estimates for sustained Homo sapiens presence inside closed-canopy tropical forest.

The methodological core of the paper is its multiproxy environmental reconstruction. Phytolith assemblages dominated by arborescent morphotypes, pollen records skewed toward humid forest taxa, and a stable-isotope profile from leaf-wax n-alkanes consistent with C3-dominated canopy vegetation collectively rule out a savanna or mosaic intermediate. The lithic assemblage itself, prepared on locally available quartz and sandstone using Levallois and discoid reduction strategies, is broadly consistent with Middle Stone Age technocomplexes documented elsewhere on the continent, but its co-occurrence with a closed-forest signal is unprecedented at this antiquity.

The result strikes directly at the savanna hypothesis, which for much of the late twentieth century positioned open grasslands as the primary cradle of modern human cognition and behavior. By demonstrating that rainforests were occupied — and presumably exploited for tubers, palm starch, fish, and small forest game — within the deep Middle Pleistocene, the Bété I dating reframes Homo sapiens as a generalist almost from inception, rather than a savanna specialist that only secondarily colonized closed-canopy environments during the Late Pleistocene dispersals. It also nudges forward the inferred origins of ecological niche construction, the ability of a species to actively shape its habitat through fire, selective harvesting, and forest gardening.

Critically, the finding implies a sampling bias in continental-scale models of human origins. Most of the dated Homo sapiens record before about 100,000 years ago derives from East African rift sedimentary basins and from southern African coastal cave deposits, both of which preserve well and have been excavated for generations. West and Central African rainforest sediments, by contrast, are acidic, biologically active, and chronically under-investigated, and they almost certainly conceal a large but currently invisible archive of early modern human behavior. The authors close by urging a renewed program of fieldwork in the Upper Guinean and Congolian forests, framed not as exploration for outlier sites but as an overdue audit of an ecosystem that may have hosted a substantial fraction of our species' formative history.

unambiguous: Having only one possible meaning or interpretation; clear.

multiproxy: Using several independent kinds of evidence to reconstruct past conditions.

arborescent: Tree-like in form or having the characteristics of trees.

isotope: A form of a chemical element with a different number of neutrons.

lithic: Relating to or made of stone, especially in archaeology.

Pleistocene: The geological epoch from about 2.6 million to 11,700 years ago.

generalist: A species or person able to thrive in many different conditions.

sedimentary: Formed by the deposition of material in layers, especially in geology.

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Lost for 150,000 Years: Côte d'Ivoire Site Pushes Back Earliest Human Rainforest Habitation by More Than Double

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