The origin of the Acheulian stone technology has long fascinated prehistorians, as the handaxe seems to signify the first tool made with predetermined shape. This proposal seeks funding to investigate the mode, tempo and causes of the Oldowan-Acheulian technology transition, 2.0-1.7 million years ago (Ma), at Gona, Afar, Ethiopia. This time period is immensely important to the study of human origins and the evolution Homo (our own genus), as it marks the emergence of Homo ergaster (erectus), the likely inventor of the Acheulian technology. Specifically, our goals are to: 1) determine the timing and nature of the Oldowan-Acheulian transition at Gona, 2) identify stone assemblages that can be technologically recognized as transitional between the two industries, 3) assess whether the transition was gradual or rapid, 4) conduct experimental-knapping using the stone raw materials actually accessed by the tool makers, and brain-imaging studies for understanding the cognitive skills of the makers, and 5) determine to what extent the transition was environmentally mediated (that is, corresponds to paleoenvironmental changes). Only a few study areas in the world have both early (~1.7 Ma) Acheulian sites and deposits that immediately precede this time. Gona is one of them, making it possible to explore its origins. In order to accomplish these goals, we plan to survey intensively the areas of Gona that have deposits dating to 2.0-1.6 Ma. We will then 1) identify and sample (through excavations) all archaeological traces of this age, 2) analyze these stone tool assemblages with respect to technologically relevant attributes, 3) sample and analyze the associated raw material sources for type, size and shape (this will also involve replication of the stone tools and brain-imaging studies), 4) conduct taphonomic study of fossil fauna for determining stone tool functions (and other bone modifying agents), and 5) document eological/paleoenvironmental contexts of each assemblage.