(Phys.org) —Researchers have carried out the biggest ever comparative study of stone tools dating to between 130,000 and 75,000 years ago found in the region between sub-Saharan Africa and Eurasia. They have discovered there are marked differences in the way stone tools were made, reflecting a diversity of cultural traditions. The study has also identified at least four distinct populations, each relatively isolated from each other with their own different cultural characteristics.