Volcanic ash left over from a huge ancient eruption has helped scientists determine that important early Homo sapiens fossils found in Ethiopia in 1967 are older than previously believed, providing fresh insight into the dawn of our species. Researchers said on Wednesday they used the geochemical fingerprints of a thick layer of ash found above the sediments containing the fossils to ascertain that it resulted from an eruption that spewed volcanic fallout over a wide swathe of Ethiopia roughly 233 000 years ago.