SEDIMENTARY deposits in the Middle Awash research area of Ethiopia’s Afar depression have yielded vertebrate fossils including the most ancient hominids known. Radioisotopic dating, geochemical analysis of interbedded volcanic ashes and biochronological considerations place the hominid-bearing deposits at around 4.4 million years of age. Sedimentological, botanical and faunal evidence suggests a wooded habitat for the Aramis hominids.