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The Oldowan Stone tool industry was named for 1.8-million-year-old (Myr) artefacts found near the bottom of Olduvai Gorge, Tanzania. Subsequent archaeological research in the Omo (Ethiopia) and Turkana (Kenya) also yielded stone tools dated to 2.3 Myr. Palaeoanthropological investigations in the Hadar region of the Awash Valley of Ethiopia, revealed Oldowan(More)
Calibration of the geological time scale is achieved by independent radioisotopic and astronomical dating, but these techniques yield discrepancies of approximately 1.0% or more, limiting our ability to reconstruct Earth history. To overcome this fundamental setback, we compared astronomical and 40Ar/39Ar ages of tephras in marine deposits in Morocco to(More)
The Hata Member of the Bouri Formation is defined for Pliocene sedimentary outcrops in the Middle Awash Valley, Ethiopia. The Hata Member is dated to 2.5 million years ago and has produced a new species of Australopithecus and hominid postcranial remains not currently assigned to species. Spatially associated zooarchaeological remains show that hominids(More)
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,(More)
The age and timing of the Permian-Triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive lead loss and contamination by indistinguishable older xenocrysts. Zircons from nine ash beds within the Shangsi and Meishan sections (China), pretreated by annealing followed by(More)
The Middle Awash study area of Ethiopia's Afar rift has yielded abundant vertebrate fossils (approximately 10,000), including several hominid taxa. 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 volcanic transition zone between the main Ethiopian rift (MER) and(More)
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(More)
The Permian-Triassic boundary records the most severe mass extinctions in Earth's history. Siberian flood volcanism, the most profuse known such subaerial event, produced 2 million to 3 million cubic kilometers of volcanic ejecta in approximately 1 million years or less. Analysis of (40)Ar/(39)Ar data from two tuffs in southern China yielded a date of 250.0(More)