During a period of major faulting and volcanism roughly 600,000 to 400,000 years ago , the Masek Beds were made . These beds contained tools from an industry made by modern humans , followed by the Ndutu Beds ( 400,000 to 32,000 years ago ) , and the Naisiusiu Beds ( 22,000 to 15,000 years ago ) . Beds above these contained tools from a Kenya-Capsian industry made by modern humans and are termed the Masek Beds ( 600,000 to 400,000 years ago ) , the Ndutu Beds ( 400,000 to 32,000 years ago ) , and the Naisiusiu Beds ( 22,000 to 15,000 years ago ) .