Australopithecus anamensis
Encyclopedia
Australopithecus anamensis (or Praeanthropus anamensis) is a stem-human species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 that lived approximately four million years ago. Nearly one hundred fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 specimens are known from Kenya
Kenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...

  and Ethiopia
Ethiopia
Ethiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...

, representing over 20 individuals.

Discovery

The first fossilized specimen of the species, though not recognized as such at the time, was a single fragment of humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....

 (arm bone) found in Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

 strata in the Kanapoi region of East Lake Turkana
Lake Turkana
Lake Turkana , formerly known as Lake Rudolf, is a lake in the Great Rift Valley in Kenya, with its far northern end crossing into Ethiopia. It is the world's largest permanent desert lake and the world's largest alkaline lake...

 by a Harvard University
Harvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...

 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
Archaeology
Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...

 Allan Morton (with Harvard University's Koobi Fora
Koobi Fora
Koobi Fora refers primarily to a region around Koobi Fora Ridge, located on the eastern shore of Lake Turkana in the territory of the nomadic Gabbra people. According to the National Museums of Kenya, the name comes from the Gabbra language:...

 Field School) discovered fragments of a specimen protruding from a partially eroded hillside east of Allia Bay, near Lake Turkana
Lake Turkana
Lake Turkana , formerly known as Lake Rudolf, is a lake in the Great Rift Valley in Kenya, with its far northern end crossing into Ethiopia. It is the world's largest permanent desert lake and the world's largest alkaline lake...

, Kenya
Kenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...

.

In 1994, the London-born Kenyan paleoanthropologist
Paleoanthropology
Paleoanthropology, which combines the disciplines of paleontology and physical anthropology, is the study of ancient humans as found in fossil hominid evidence such as petrifacted bones and footprints.-19th century:...

 Meave Leakey
Meave Leakey
Meave G. Leakey is together with her husband Richard Leakey one of the most renowned contemporary paleontologists. She studies the origin of mankind in Africa.-Flat-Faced Man of Kenya:...

 and archaeologist Alan Walker
Alan Walker (academic)
Alan Walker , is Evan Pugh Professor of Biological Anthropology and Biology at the Pennsylvania State University. He received his B.A. from Cambridge University in 1962, and his Ph.D. from the University of London in 1967. He was also awarded a MacArthur Fellowship "genius grant" in 1988.Dr...

 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
Common Chimpanzee
The common chimpanzee , also known as the robust chimpanzee, is a great ape. Colloquially, the common chimpanzee is often called the chimpanzee , though technically this term refers to both species in the genus Pan: the common chimpanzee and the closely related bonobo, formerly called the pygmy...

 (Pan troglodytes) but whose teeth bear a greater resemblance to those of a human
Human
Humans are the only living species in the Homo genus...

.

In 1995, Meave Leakey and her associates, taking note of differences between Australopithecus afarensis
Australopithecus afarensis
Australopithecus afarensis is an extinct hominid that lived between 3.9 and 2.9 million years ago. A. afarensis was slenderly built, like the younger Australopithecus africanus. It is thought that A...

and the new finds, assigned them to a new species, A. anamensis, deriving its name from the Turkana
Turkana language
Turkana is the language of the Turkana people of Kenya, numbering about 340,000.It is one of the Eastern Nilotic languages, and is closely related to Karamojong, Jie and Teso of Uganda, to Toposa spoken in the extreme southeast of Sudan, and to Nyangatom in the Sudan/Ethiopia Omo valley borderland;...

 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
Tree climbing
Tree climbing is a recreational or functional activity consisting of ascending and moving around in the crown of trees.Use of a rope, helmet, and harness are the minimum requirements to ensure the safety of the climber. Other equipment can also be used depending on the experience and skill of the...

 was one behavior retained by early hominins until the appearance of the first Homo
Homo (genus)
Homo is the genus that includes modern humans and species closely related to them. The genus is estimated to be about 2.3 to 2.4 million years old, evolving from australopithecine ancestors with the appearance of Homo habilis....

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 datting to about 4.1–4.2 million years ago. Specimens have been found between two layers of volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...

, 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
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....

). 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
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...

 yet recovered and the earliest Australopithecus femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

. The find was in an area known as Middle Awash
Middle Awash
The Middle Awash is an archaeological site along the Awash River in Ethiopia's Afar Depression. A number of Pleistocene and late Miocene hominid remains have been found at the site, along with some of the oldest known Olduwan stone artifacts and patches of fire-baked clay, disputed evidence of the...

, 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
Ardipithecus
Ardipithecus is a very early hominin genus. Two species are described in the literature: A. ramidus, which lived about 4.4 million years ago during the early Pliocene, and A. kadabba, dated to approximately 5.6 million years ago ....

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
Timeline of evolution
This timeline of evolution of life outlines the major events in the development of life on planet Earth since it first originated until the present day. In biology, evolution is any change across successive generations in the heritable characteristics of biological populations...

.

See also


External links


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