Australopithecus anamensis

Australopithecus anamensis is a species of Australopithecus.^[1] Its scientific name is abbreviated as A. anamensis.

Australopithecus anamensis Temporal range: Pliocene
Fossils
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Primates
Family:	Hominidae
Subfamily:	Homininae
Genus:	Australopithecus
Binomial name
Australopithecus anamensis Leakey et al., 1995

A. anamensis is the earliest known australopithecine species.^[2][3] It lived from around 4.3 million years ago^[4] to around 3.8 million years ago.^[5]

A. anamensis lived in East Africa. Paleoanthropologists have found over 100 A. anamensis fossils in Kenya^[6] and Ethiopia^[7], from 20 separate individuals.

Name

The name Australopithecus comes from the Latin word australo (meaning ‘southern’) and the Greek word pithecus (meaning ‘ape’).

The word anamensis is based on the word anam, which means "lake" in the Turkana language.^[8] (This language is spoken in the area where A. anamensis fossils were first discovered.) The word "lake" here refers to how A. anamensis once lived next to lakes.^[9]

Together, the name Australopithecus anamensis means "southern ape of the lake."^[9]

Evolution

In human evolution, Australopithecus anamensis is the intermediate species between Ardipithecus ramidus and Australopithecus afarensis.^[10] This means that A. anamensis descended from Ardipithecus ramidus, and is the ancestor of A. afarensis^[11][12].

Even though A. anamensis evolved into A. afarensis, it did not replace it. The two species existed at the same time for at least 100,000 years.^[11]

Description

A. anamensis was around the same size as a modern chimpanzee (pictured)

The location of A. anamensis fossils show that this species lived in forests and woodlands that grew around lakes.^[11]

A. anamensis had a combination of human-like and ape-like traits.^[12] It was bipedal: it regularly walked upright.^[13] However, its long arms and wrist bones suggest that it also spent time climbing trees.^[5][11] It may have sometimes walked on its knuckles.^[14]

Based on fossils, scientists estimate that A. anamensis was about the same size as modern chimpanzees.^[5] Like in modern gorillas and orangutans, females were much smaller than males.^[5] (This is called sexual dimorphism.)

Only one A. anamensis skull has been found. That individual had a small brain, smaller than A. afarensis.^[15]

Diet

Based on analysis of wear patterns on fossil teeth, A. anemensis had about the same diet as a modern gorilla. Their diet stayed the same regardless of what environment they lived in.^[16] A. anamensis mostly ate plants, including both fruits and tougher foods like nuts.^[11][17]

Fossils

First specimen

The first fossilized specimen of the species, though not recognized as such at the time, was a single arm bone. It was 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.

1987 specimen

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 sticking out of a hillside east of Allia Bay, near Lake Turkana, Kenya.

Allia Bay site

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".