Australopithecus_anamensis

Australopithecus anamensis

Australopithecus anamensis is a fossil species of Australopithecus. The first fossilized specimen of the species, though not recognized as such at the time, was a single 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. Six years later 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 are much more similar 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".

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 similar to Australopithecus afarensis and may as well be its direct predecessor. A. anamensis is thought to have lived from 4.1 and 3.9 million years ago. The older specimens were 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, a fragment of humerus that was 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 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 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.

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