Have microlith, will travel

Small stone tools – probably arrow and spear tips, such as a microlith – found in a cave in Sri Lanka are rewriting the story of how humans moved into challenging new environments nearly 50,000 years ago.

New radiocarbon dating shows that a microlith is the oldest found in South Asia and among the oldest in all Eurasia. The tools appear to have been part of a “survival toolkit” that enabled Homo sapiens to move into rainforests and other difficult settings much earlier than previously thought.

Until recently, rainforests were seen as barriers to human migration, with disease, dangerous animals, the scarcity of carbohydrate-rich plants and limited resources all posing challenges. Therefore, research on human migration in Asia has focused on the coast and savannah.

But over the past decade, growing archaeological evidence has shown H. sapiens lived in tropical rainforests in South Asia, South-East Asia and Melanesia between 45,000 and 36,000 years ago.

Missing from this picture was a good understanding of the technology humans used to survive.

So, the discovery of a huge repository of microliths in the Fa-Hien Lena Cave in Sri Lanka’s evergreen rainforest piqued the interest of researchers from the Max Planck Institute for the Science of Human History and colleagues from Sri Lankan and other international institutions.

Excavations in 2009, 2010 and 2012 yielded an extraordinary 9,216 artefacts, and these have finally been closely analysed for the first time. 

The researchers, with funding from the National Geographic Society, found that a microlith – stone tools less than 40mm long – is up to 48,000 years old, making them at least as old as similar tools associated with H. sapiens in Europe.

Writing in PLOS One, they say the sophisticated, miniaturised tools used by the occupants of the Sri Lankan caves changed little over the long period of human occupation, which ended only 4,000 years ago.

This suggests they were remarkably successful.

In Europe and Africa, the earliest appearance of hewn stone tools is linked to hunting medium and large-sized animals in grassland or woodland settings, or as adaptations to risky environments during periods of climatic change.

But the small, quartz microliths found in Fa-Hien Lena Cave were more likely to have been used to hunt tree-dwelling prey and small mammals. The miniaturisation of stone tool technology is seen as a major step in the development of technologies such as the bow and arrow.

The researchers conclude that our ancestors were able to adapt their stone technology to the requirements of new environments, making microliths a flexible toolkit for survival as H. sapiens spread out of Africa.

Intriguingly, the idea that early humans in Sri Lanka could have produced microliths so long ago was first floated in the 1980s but was overlooked because scientists did not believe humans there could have produced such tools before European humans.

Michael Petraglia, one of the paper’s authors, says more research is underway on bone tools and fragments from Fa-Hien Lena Cave.

“Whatever the results, these miniaturised stone tools place Sri Lanka in a central position in terms of discussing technological sophistication among our species.”

Related reading: Stone tools improved over millennia