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

Abstract

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 the Afar rift, sediments along the western Afar rift margin in the Middle Awash provide a unique window on the Late Miocene of Ethiopia. These deposits have now yielded the earliest hominids, described in an accompanying paper and dated here to between 5.54 and 5.77 Myr. These geological and palaeobiological 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, volcanic, climatic and geomorphic processes. A similar wooded habitat also has been suggested for the 6.0 Myr hominoid fossils recently recovered from Lukeino, Kenya. These findings require fundamental reassessment of models that invoke a significant role for global climatic change and/or savannah habitat in the origin of hominids.

Taphonomic analysis of skeletal remains from chimpanzee hunts at Ngogo, Kibale National Park, Uganda

“…Finally, pre-technological hominins were similar in body size to modem chimpanzees (McHenry, 1992), lived in more closed environments than later hominins (WoldeGabriel et al, 1994;Pickford and Senut, 2001;WoldeGabriel et al, 2001;Vignaud, et al, 2002), and may have retained some tree-climbing adaptations (Richmond, 1998;Hailie-Selassie, 2001;Senut et al, 2001;Ward, 2002). We suggest that if pre-stone toolusing Pliocene hominins hunted and consumed small sized prey, the taphonomic signature of that hunting behavior would be more similar to chimpanzee consumption of small prey than Oldowan hominin stone tool-assisted butchery of larger prey.…”

“…The colobine remains from Toros-Menalla is a single damaged maxilla , but the faunal assemblage from Kapsomin is dominated by small to medium ruminants and colobine monkeys that Pickford and Senut (2001) interpret to be the prey remains of a leopard-like cat. Ardipithecus ramidus kadabha specimens from the Central Awash Complex (at 5.54•5.77 Ma) were deposited in a wooded and possibly humid environment (WoldeGabriel et al, 2001). The fauna associated with Ardipithecus ramidus from Aramis, Ethiopia (at 4.4 Ma) is dominated by colobine monkeys (over 30% of all identifiable vertebrates in the assemblage) in a closed, wooded environment (WoldeGabriel et al, 1994).…”

A multidisciplinary reconstruction of Palaeolithic nutrition that holds promise for the prevention and treatment of diseases of civilisation

“…The palaeo-environment of Orrorin (about 6 Mya) was probably characterised by open woodland, with dense stands of trees in the vicinity and possibly fringing the lake margin and/or streams that drained into the lake (157) . Ardipithecus kadabba (5·6 Mya) remains are associated with wet and closed, grassy woodland and forest habitats around lake or river margins (158) . Ardipithicus ramidus (4·4 Mya) lived in or near a groundwater-supported grassy woodland to forest (159) .…”

The Pliocene hominin diversity conundrum: Do more fossils mean less clarity?

“…Orrorin tugenensis and Ar. kadabba are 6.0-5.7 Ma and 6.4-5.5 Ma, respectively (35)(36)(37)). There appears to be some degree of overlap in the temporal distribution of these three taxa, indicating possible taxonomic diversity in the hominin clade from 6 Ma onwards (Fig.…”