Isotopes in tooth and bone
In the dense rainforests of Sri Lanka, archaeological sites like Batadomba-lena and Fa-Hien Lena hold the remains of anatomically modern humans who lived as far back as 48,000 years ago. For a long time, tropical rainforests were considered difficult environments for early hunter-gatherers. The story of "Balangoda Man," a name given to these prehistoric people, changes that perspective. The primary evidence comes from stable isotope analysis of their skeletal remains.
Scientists analyzed the carbon (δ¹³C) and oxygen (δ¹⁸O) isotopes in tooth enamel from individuals dating back tens of thousands of years. These chemical signatures are a permanent record of diet. The results showed consistently low δ¹³C values, which shows a diet sourced from a closed-canopy rainforest. Foods from open grasslands or marine environments produce distinctly different, higher isotopic signatures. This proves these early Sri Lankans were not occasional visitors to the forest but were highly specialized, full-time rainforest dwellers. This dedicated rainforest adaptation is one of the earliest examples found for Homo sapiens anywhere in the world.