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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


Ardipithecus ramidus (4.4 million years ago)*

*Because fossil evidence for Ardipithecus ramidus is scant, a range of dates for when this species lived is not available.

Species Description:

Ardipithecus ramidus was discovered in December 1992. Although not nearly as old as Orrorin tugenensis, Ar. ramidus is much more widely accepted by the scientific community as a hominid than is O. tugenensis, and thus is considered by some to be the oldest-known hominid.

A partial skeleton and indirect evidence from skeletal fragments indicate that Ar. ramidus may have walked upright. Although considered to be one of the most primitive hominids, Ar. ramidus shares some novel characteristics with much later hominids, namely aspects of its teeth. The molars of Ar. ramidus are smaller than are those of any of the Australopithecus species.

Other fossils found with Ar. ramidus suggest that it may have been a woodland forest dweller. This may modify current theories about why hominids became bipedal in the first place. Walking upright has typically been linked to movement onto the savanna.

(Note: This species has not yet been fully described because some of the specimens have been difficult to extract from the surrounding rock.)

Fossil Finds:

Estimated age: 4.4 million years
Date of discovery: 1992, 1993
Location: Aramis, Ethiopia

A partial lower jaw from a child is one of several fossils known for this species. This partial jaw, catalogued as ARA-VP-1/129, shows very primitive tooth structure relative to later hominid species. Other fossils -- including teeth, an adult mandible, pieces of a skull, and several arm bones -- show an interesting mix of primitive and advanced characteristics.

-> Go to Australopithecus anamensis

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