Just when scientists thought they had this whole ancient human migration thing sort of figured out, a new discovery comes along to disrupt them.
A trove of more than 7,000 unearthed ancient stone tools now suggests early humans might have reached Asia earlier than previously thought – as much as 385,000 years ago.
As is often the case in science, the find means more questions than answers.
The Attirampakkam archaeological site in India has been excavated since its discovery in 1863. Archaeologists with the Sharma Centre for Heritage Education in India have been excavating the site since 1999.
Layers in the sediment where the tools were found are dated using luminescence dating, a method that measures the last time crystals saw light at the surface.
The oldest layer of sediment is found 4 meters (13 feet) below the surface and contains large, chunky hand-axes made in the “Acheulean” fashion. Going up another layer, archaeologists found more advanced tools typical of the Middle Stone Age and made using what is known as the "Levallois" technique.
Previously, the oldest Middle Stone Age tools in India dated back 140,000 to 46,000 years ago.
The last layer, which dates back about 73,000 years, is completely void of tools. Archaeologists say this means the site was likely abandoned.
It has scientists scratching their heads.
Because there are no fossil remains accompanying the tools, scientists can’t definitively say what type of hominin lived here, but they do have one pretty solid theory.
It probably wasn’t Homo sapiens, whose oldest remains were found in Morocco and date back 315,000 years. Just last week researchers discovered the oldest human remains outside of Africa, dating back as recently as 185,000 years ago.
The study, published in Nature, suggests that the end of the Acheulean culture and the beginning of the Middle Stone Age occurred much earlier than previously thought, and could indicate that multiple waves of people left Africa more than 60,000 years ago.
It also suggests a shared knowledge of technology meaning that local groups likely interacted at global levels.
The shift in tool methodologies helps archaeologists understand how people moved around and how the groups interacted with each other. In this case, the shift to smaller, more advanced tools (rather than blunter, archaic axes) means a behavioral change occurred in India around the same time as in Africa and Europe
This means major changes in Stone Age technologies were less dependent on movements from Africa than previously thought.
Researching migrations and settlements is crucial for understanding the origins and early evolution of hominins, a group that includes us. Because of its geographic location, India is a prime area to study. Even so, researchers say there are too few archaeological excavations underway and further research is required.