[Homestead] Evolution, your 6,000,000 years old ancestor
tvoivozd at infionline.net
Sat Sep 4 14:42:46 EDT 2004
Chimp-sized Hominid Walked Upright On Two Legs Six Million Years Ago
University Park, Pa. -- Recent fossil evidence suggests that a hominid,
the size of a chimp, walked upright on two legs in Kenya's Tugen Hills,
over 6 million years ago --- about 3 million years earlier than "Lucy,"
the most famous early biped in our lineage.
Left: Reconstruction of the fossil bone from CT slices. The vertical
line indicates the plane of the view shown on the right. (Image courtesy
of Penn State)
Speech Linked With Bipedality By UMBC Professor
New Species Of Human Ancestor
New Fossil Discoveries Clinch Ancient Age Of Human Ancestor
Dr. Robert Eckhardt, professor of developmental genetics and
evolutionary morphology, Laboratory of Comparative Morphology and
Mechanics (LCMM), Department of Kinesiology at Penn State, led the U.S.
research team responsible for analysis of the CT scans of the internal
structure of the fossil bone. Eckhardt says, "We have solid evidence of
the earliest upright posture and bipedalism securely dated to six
The evidence is detailed in the current (Sept. 3) issue of Science in a
report, "External and Internal Morphology of the BAR 1002'00 Orrorin
tugenensis Femur." Eckhardt's co-authors are Karl Galik, Orthopedic
Biomechanics Laboratory, Allegheny General Hospital, Pittsburgh, Pa.;
Brigitte Senut, Department of Earth History, National Museum of Natural
History, Paris, France; Martin Pickford, who holds the chair of
paleoanthropology and prehistory at the College of France and at the
Department of Earth History of the National Museum of Natural History,
Paris, France; Dominique Gommery, National Center for Scientific
Research, Paris, France; Jacques Treil, Radiology Department, Pasteur
Clinic, Toulouse, France; and Adam Kuperavage, a graduate student in
Penn State's LCMM.
The fossil the team studied is part of a left thighbone unearthed nearly
four years ago by Senut and Pickford at their dig in the Kenyan Lukeino
Formation. The fragment includes the intact head of the left thighbone
-- the ball that is inserted into the hip socket joint -- plus the bony
neck that connects the ball to the thighbone shaft as well as part of
the thighbone shaft.
Measurements, chiefly carried out by Dr. Galik, show that the fossil
bone is about the same size as a chimpanzee's. However, CT scans of the
interior of the bone reveal that the neck connecting the ball to the
shaft is thinner on top than it is on the bottom, a sign the researchers
say that the individual from which it came walked on two legs.
Eckhardt says, "In present day chimps and gorillas, the thicknesses in
the upper and lower parts of that bone are approximately equal. In
modern humans, the bone on top is thinner than on the bottom by a ratio
of one to four or more. The ratio in this fossil is one to three."
The ratio in the fossil is evidence for transition to an upright posture
and habitual bipedal gait the researchers argue. In addition, Eckhardt
notes, because walking upright is the essential mark of a hominid, the
ratio is functional evidence that the bones fossilized at Lukeino were
The researchers write, "In known features, external and internal,
BR1002'00 exhibits a total morphological pattern distinct from African
apes, diagnostic of bipedal locomotion and appropriate for a population
standing at the dawn of the human lineage."
The imaging research was supported, in part, by grants from the American
Philosophical Society and from Sigma Xi.
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