The archaeologists found an influx of obsidian

 The archaeologists found an influx of obsidian

 at level C at the site, which suggests that an ancient river flooded periodically more than 1.2 million years ago, depositing obsidian at Melka Kunture.

Ancient hominins "are very often depicted as barely surviving, struggling with a hostile and changing environment," Mussi said in an email from the field in Melka Kunture. "Here we prove instead that they were clever individuals, who did not miss the opportunity of testing any resource they discovered."

This nearly exclusive use of obsidian at Level C of Simbiro III is unusual during the Early Stone Age, which ranged from about 3.3 million to 300,000 years ago, the researchers said. Obsidian tools can possess extraordinarily sharp cutting edges, but the volcanic glass is brittle and difficult to craft without smashing. As such, obsidian generally only found extensive use in stone tool manufacture beginning from the Middle Stone Age, which ranged from about 300,000 to 50,000 years ago, they said.