Scientists have dated sharp-edged flakes of stone found in the fine-grained sediments of a dry riverbed in the Afar region of Ethiopia to between 2.52 and 2.60 million years ago, pushing back by more than 150,000 years the earliest date when it is known that humans made stone tools.

• Awhen it is known that humans made  
• Bat which it is known that humans had made  
• Cat which humans are known to have made  
• Dthat humans are known to be making  
• Eof humans who were known to make