Africa: Humans Lived in African Rainforests 150,000 Years Ago, Far Earlier Than Believed - New Research

Humans first appeared in Africa about 300,000 years ago. However, scientists are still unsure about our early environment. Previously, researchers believed grasslands and savannahs were where humans evolved. Rainforests were thought to be barriers to human expansion.

Recent research in Asia challenges this view. Evidence shows advanced behaviors in ancient rainforest settings. For example, humans lived in rainforests on Sumatra, Indonesia, 70,000 years ago. They adapted well to the rainforest challenges.

At Niah Cave in Borneo, people processed toxic plants 45,000 years ago. This was shortly after their arrival there around 46,000 years ago. In Sri Lanka, evidence shows reliance on rainforest resources from at least 36,000 years ago.

These findings suggest that humans lived in rainforests before leaving Africa. Until now, the oldest evidence of African rainforest habitation was only 18,000 years old. Our new study extends this date significantly back to 150,000 years ago.

Our research took place in Côte d'Ivoire. It began in the 1980s at the Bété I site by Professor François Yiodé Guédé. His initial study revealed a long sedimentary sequence with stone tools.

This site has one of Africa's few long histories of sediment layers. The sequence is about 14 meters deep and contains many preserved tools. Over 1,500 stone tools were found during excavations from the 1980s and 1990s.

However, we could not determine the age or ecology of these tools then. We returned to the site after 36 years and located the Bété I sequence again. We collected sediment samples for analysis using various methods.

To date the sediment with stone tools, we used two techniques: optically stimulated luminescence and electron spin resonance. These methods helped us determine how old quartz grains were at different layers.

We also examined pollen and phytoliths (plant silica concretions) from the sediment samples. Our analyses showed that by 150,000 years ago, this site was heavily wooded with humid forest characteristics.

Low levels of grass pollen indicated it wasn't just a narrow forest strip but a dense woodland ecosystem featuring oil palms and other important plants.

Our findings reveal that ecological diversity is central to human history. Humans have adapted to various habitats since early times. This adaptability makes us unique among species.

The discovery's location in west Africa emphasizes exploring different regions for a fuller understanding of early human prehistory. In west Africa specifically, archaeologists have found distinct cultural behaviors from this period.

For instance, at Ravin Blanc I site in Senegal's Falémé valley dating back around 125,000 years shows unique stone tools compared to those found elsewhere like Bargny sites nearby.