http://www.ldeo.columbia.edu/~peter/site/Papers_files/deMenocal.2004.pdf

African climate change and faunal evolution during the Pliocene-Pleistocene

The Evolution of Language

Although few hunter-gatherers or foragers exist today, they are well documented in the ethnographic record. Anthropologists have been eager to study them since they assumed foragers represented a lifestyle that existed everywhere before 10,000 years ago and characterized our ancestors into some ill-defined but remote past. In the past few decades, that assumption has been challenged on several grounds. Ethnographically described foragers may be a biased sample that only continued to exist because they occupied marginal habitats less coveted by agricultural people.3 In addition, many foragers have been greatly influenced by their association with more powerful agricultural societies.4 It has even been suggested that Holocene foragers represent a new niche that appeared only with the climatic changes and faunal depletion at the end of the last major glaciation.5 Despite these issues, the ethnographic record of foragers provides the only direct observations of human behavior in the absence of agriculture, and as such is invaluable for testing hypotheses about human behavioral evolution.6.

Hunter-Gatherers and Human Evolution

A general problem in biology is how to incorporate information about evolutionary history and adaptation into taxonomy. The problem is exemplified in attempts to define our own genus, Homo. Here conventional criteria for allocating fossil species to Homo are reviewed and are found to be either inappropriate or inoperable. We present a revised definition, based on verifiable criteria, for Homo and conclude that two species, Homo habilis and Homo rudolfensis, do not belong in the genus. The earliest taxon to satisfy the criteria is Homo ergaster, or early African Homo erectus, which currently appears in the fossil record at about 1.9 million years ago.

The Human Genus

Human evolutionary scholars have long supposed that the earliest stone tools were made by the genus Homo and that this technological development was directly linked to climate change and the spread of savannah grasslands. New fieldwork in West Turkana, Kenya, has identified evidence of much earlier hominin technological behaviour. We report the discovery of Lomekwi 3, a 3.3-million-year-old archaeological site where in situ stone artefacts occur in spatiotemporal association with Pliocene hominin fossils in a wooded palaeoenvironment. The Lomekwi 3 knappers, with a developing understanding of stone's fracture properties, combined core reduction with battering activities. Given the implications of the Lomekwi 3 assemblage for models aiming to converge environmental change, hominin evolution and technological origins, we propose for it the name 'Lomekwian', which predates the Oldowan by 700,000 years and marks a new beginning to the known archaeological record.

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3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya

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 Ethiopia1, revealed Oldowan assemblages in the adjacent Gona River drainage2. We conducted field work in the Gona study area of Ethiopia between 1992 and 1994 which resulted in additional archaeological discoveries as well as radio-isotopic age control and a magnetic polarity stratigraphy of the Gona sequence. These occurrences are now securely dated between 2.6–2.5 Myr. The stone tools are thus the oldest known artefacts from anywhere in the world. The artefacts show surprisingly sophisticated control of stone fracture mechanics, equivalent to much younger Oldowan assemblages of Early Pleistocene age. This indicates an unexpectedly long period of technological stasis in the Oldowan.

K. Mowbray

Papers

2.5-million-year-old stone tools from Gona, Ethiopia