Earliest Stone-Tipped Projectiles from the Ethiopian Rift Date to >279,000 Years Ago Sahle, Yonatan ; Hutchings, W. Karl ; Braun, David R. ; Sealy, Judith C. ; Morgan, Leah E. ; Negash, Agazi ; Atnafu, Balemwal Abstract Publication: PLoS ONE Pub Date: November 2013 DOI: 10.1371/journal.pone.0078092 Bibcode: 2013PLoSO...878092S