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Origins of Humankind
The Hominid Family Tree

Orrorin tugenensis
(6 mya)

Ardipithecus ramidus
(4.4 mya)

Australopithecus anamensis
(4.2 to 3.9 mya)

Australopithecus afarensis
(3.6 to 2.9 mya)

Kenyanthropus platyops
(3.5 to 3.3 mya)

Australopithecus africanus
(3 to 2 mya)

Australopithecus aethiopicus
(2.7 to 2.3 mya)

Australopithecus garhi
(2.5 mya)

Australopithecus boisei
(2.3 to 1.4 mya)

Homo habilis
(2.3 to 1.6 mya)

Homo erectus
(1.8 to 0.3 mya)

Australopithecus robustus
(1.8 to 1.5 mya)

Homo heidelbergensis
(600 to 100 tya)

Homo neanderthalensis
(250 to 30 tya)

Homo sapiens
(100 tya to present)

mya = millions of years ago        tya = thousands of years ago


Australopithecus aethiopicus (2.7 to 2.3 million years ago)

Species Description:

Australopithecus aethiopicus may be an ancestor of two later species, Australopithecus robustus and Australopithecus boisei. The species has a peculiar mixture of primitive and highly derived traits relative to earlier species.

Brain size of A. aethiopicus is comparable to that of modern apes and the much-earlier A. afarensis. Other skull traits appear to be novel adaptations, some of which probably allowed A. aethiopicus to exploit tougher food sources. The massive face was flat or concave with no forehead.

A very large sagittal crest (a ridge of bone running along the top of the skull) and other heavily reinforced areas of the skull would have provided strong points of attachment for chewing muscles. Powerful chewing muscles, paired with the species' extremely large and thickly enameled molars and premolars, suggest that A. aethiopicus ate very tough, grainy foods that required a great deal of processing.

Fossil Finds:

The Black Skull
Estimated age: 2.6 million years
Date of discovery: 1984
Location: Lake Turkana, Kenya

This cranium, with its mix of primitive and advanced characteristics, is described by some as a nearly perfect intermediate between A. afarensis and A. boisei. The fossil suggests that A. aethiopicus was a transitional species.

-> Go to Australopithecus garhi

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