Geology and palaeontology of the Late Miocene Middle Awash valley, Afar rift, Ethiopia

The Middle Awash study area of Ethiopia's Afar rift has yielded abundant ve rtebrate fossils (approximate to 10,000), including several hominid taxa(1- 4). The study area contains a long sedimentary record spanning Late Miocene (5.3-11.2 Myr ago) to Holocene times. Exposed in a unique tectonic and vol canic transition zone between the main Ethiopian rift (MER) and the Afar ri ft, sediments along the western Afar rift margin in the Middle Awash provid e a unique window on the Late Miocene of Ethiopia. These deposits have now yielded the earliest hominids, described in an accompanying paper(5) and da ted here to between 5.54 and 5.77 Myr. These geological and palaeobiologica l data from the Middle Awash provide fresh perspectives on hominid origins and early evolution. Here we show that these earliest hominids derive from relatively wet and wooded environments that were modulated by tectonic, vol canic, climatic and geomorphic processes. A similar wooded habitat also has been suggested for the 6.0 Myr hominoid fossils recently recovered from Lu keino, Kenya(6). These findings require fundamental reassessment of models that invoke a significant role for global climatic change and/or savannah h abitat in the origin of hominids.