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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


Orrorin tugenensis (6 million years ago)*

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

Species Description:

If Orrorin tugenensis is truly a hominid as its discoverers describe it, the species is by far the oldest-known member of the family to which humans belong. In fact, at 6 million years old, O. tugenensis lived near the time when genetic analyses suggest our oldest hominid ancestor split from the oldest ancestor of the great apes. This means that there's a chance O. tugenensis could be the proverbial "missing link" -- or at least one of them.

Certain features, like the teeth of O. tugenensis, suggest this species could even be more closely related to Homo sapiens than the many Australopithecus species it predates. Like our molars, the molars of O. tugenensis were small compared to any of the australopithecine teeth. Their teeth also had very thick enamel like ours.

Grooves in the femurs of O. tugenensis, presumably points where muscles and ligaments attached, suggest that the species was bipedal. Unfortunately, much about this species, including the suggested close relationship between it and Homo sapiens, is extremely speculative and hotly contested.

Fossil Finds:

Millennium Ancestor

Millennium Ancestor
Estimated age: 6 million years
Date of discovery: 2000
Location: Kapsomin, Kenya

Evidence for this species is made up of 13 fossils, including a partial femur, bits of a lower jaw, and several teeth. One of the few things about O. tugenensis that is not controversial is its age. Sediments in which the bones were found have consistently been dated at 6 million years old, making O. tugenensis the oldest hominid by far, if in fact the species is a hominid.

-> Go to Ardipithecus ramidus

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