Temporal range: Pliocene
M.G. Leakey et al., 1995
Australopithecus anamensis (or Praeanthropus anamensis) is a stem-human species that lived approximately four million years ago. Nearly one hundred fossil specimens are known from Kenya  and Ethiopia, representing over 20 individuals.
The first fossilized specimen of the species, though not recognized as such at the time, was a single fragment of humerus (arm bone) found in Pliocene strata in the Kanapoi region of East Lake Turkana by a Harvard University research team in 1965. The specimen was tentatively assigned at the time to Australopithecus and dated about four million years old.
Little additional information was uncovered until 1987, when Canadian archaeologist Allan Morton (with Harvard University's Koobi Fora Field School) discovered fragments of a specimen protruding from a partially eroded hillside east of Allia Bay, near Lake Turkana, Kenya.
In 1994, the London-born Kenyan paleoanthropologist Meave Leakey and archaeologist Alan Walker excavated the Allia Bay site and uncovered several additional fragments of the hominid, including one complete lower jaw bone which closely resembles that of a common chimpanzee (Pan troglodytes) but whose teeth bear a greater resemblance to those of a human.
In 1995, Meave Leakey and her associates, taking note of differences between Australopithecus afarensis and the new finds, assigned them to a new species, A. anamensis, deriving its name from the Turkana word anam, meaning "lake". Leakey determined that this species was independent of many others. It does not represent an intermediate species of any type.
Although the excavation team did not find hips, feet or legs, Meave Leakey believes that Australopithecus anamensis often climbed trees. Tree climbing was one behavior retained by early hominins until the appearance of the first Homo species about 2.5 million years ago. A. anamensis shares many traits with Australopithecus afarensis and may well be its direct predecessor. Fossil records for A. anamensis have been dated to between 4.2 and 3.9 million years ago, with recent findings from stratigraphic sequences dating to about 4.1–4.2 million years ago. Specimens have been found between two layers of volcanic ash, dated to 4.17 and 4.12 million years, coincidentally when A. afarensis appears in the fossil record.
The fossils (twenty one in total) include upper and lower jaws, cranial fragments, and the upper and lower parts of a leg bone (tibia). In addition to this, the aforementioned fragment of humerus found thirty years ago at the same site at Kanapoi has now been assigned to this species.
In 2006, a new A. anamensis find was officially announced, extending the range of A. anamensis into north east Ethiopia. These new fossils, sampled from a woodland context, include the largest hominid canine tooth yet recovered and the earliest Australopithecus femur. The find was in an area known as Middle Awash, home to several other more modern Australopithecus finds and only six miles (9.7 kilometers) away from the discovery site of Ardipithecus ramidus, the most modern species of Ardipithecus yet discovered. Ardipithecus was a more primitive hominid, considered the next known step below Australopithecus on the evolutionary tree. The A. anamensis find is dated to about 4.2 million years ago, the Ar. ramidus find to 4.4 million years ago, placing only 200,000 years between the two species and filling in yet another blank in the pre-Australopithecus hominid evolutionary timeline.
|This article needs additional citations for verification. (December 2009)|
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- M. G. Leakey, C. S. Feibel, I. McDougall, C. Ward & A. Walker (1998-05-07). "New specimens and confirmation of an early age for Australopithecus anamensis". Nature 393 (6680): 62–66. Bibcode:1998Natur.393...62L. doi:10.1038/29972. PMID 9590689.
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- McHenry, Henry M (2009). "Human Evolution". In Michael Ruse & Joseph Travis (eds). Evolution: The First Four Billion Years. pp. 256–280. ISBN 978-0-674-03175-3. (see pp.263-265)
- Borenstein, Seth. "New Fossil Links Up Human Evolution". The Associated Press. Retrieved 2006-04-13.[dead link]
|Wikimedia Commons has media related to Australopithecus anamensis.|
- (ArchaeologyInfo.com) C. David Kreger, "Australopithecus anamensis"
- PBS Origins of Humankind
- Article about 2007 discovery (July 2007)
- Australopithecus anamensis - The Smithsonian Institution's Human Origins Program