title: Early Pliocene hominids from Gona, Ethiopia.
abstract: Comparative biomolecular studies suggest that the last common ancestor of humans and chimpanzees, our closest living relatives, lived during the Late Miocene-Early Pliocene. Fossil evidence of Late Miocene-Early Pliocene hominid evolution is rare and limited to a few sites in Ethiopia, Kenya and Chad. Here we report new Early Pliocene hominid discoveries and their palaeoenvironmental context from the fossiliferous deposits of As Duma, Gona Western Margin (GWM), Afar, Ethiopia. The hominid dental anatomy (occlusal enamel thickness, absolute and relative size of the first and second lower molar crowns, and premolar crown and radicular anatomy) indicates attribution to Ardipithecus ramidus. The combined radioisotopic and palaeomagnetic data suggest an age of between 4.51 and 4.32 million years for the hominid finds at As Duma. Diverse sources of data (sedimentology, faunal composition, ecomorphological variables and stable carbon isotopic evidence from the palaeosols and fossil tooth enamel) indicate that the Early Pliocene As Duma sediments sample a moderate rainfall woodland and woodland/grassland.
authors.affiliation: CRAFT Stone Age Institute, Indiana University, 1392 West Dittemore Road, Gosport, Indiana, 47433-9531, USA. ssemaw@indiana.edu
authors.forename: Sileshi
authors.initials: S
authors.lastname: Semaw
authors.forename: Scott W
authors.initials: SW
authors.lastname: Simpson
authors.forename: Jay
authors.initials: J
authors.lastname: Quade
authors.forename: Paul R
authors.initials: PR
authors.lastname: Renne
authors.forename: Robert F
authors.initials: RF
authors.lastname: Butler
authors.forename: William C
authors.initials: WC
authors.lastname: McIntosh
authors.forename: Naomi
authors.initials: N
authors.lastname: Levin
authors.forename: Manuel
authors.initials: M
authors.lastname: Dominguez-Rodrigo
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Rogers
mesh_terms: D000818:Animals; D003743:Dental Enamel / Q000737:chemistry; D004777:Environment; D005002:Ethiopia; D005580:Fossils; D049690:History, Ancient; D015186:Hominidae / Q000033:anatomy & histology*; D007568:Jaw / Q000033:anatomy & histology; D006109:Poaceae; D011891:Rain; D013997:Time Factors; D014070:Tooth / Q000033:anatomy & histology / Q000737:chemistry; D014197:Trees