Embargoed until: 2 p.m. EDT
July 11, 2001
NSF PR 01-57

Media Contact:
Bill Noxon
(703) 292-8070/wnoxon@nsf.gov


Program Contact:
Mark Weiss
(703) 292-7321/mweiss@nsf.gov


Anthropologists Announce Discovery In Ethiopia Of Earliest Human Ancestors
Discovery of bones and teeth date fossils back more than 5.2 million years

     A National Science Foundation (NSF)-supported international
team of researchers has announced it has discovered the remains
of the earliest known human ancestor, dating to between 5.2 and
5.8 million years ago.


     The fossil finds, reported in the July 12 issue of Nature,
were made over a four-year period in Ethiopia's Middle Awash
study area, about 140 miles northeast of the capital, Addis
Ababa.  To the team of scientists, the discovery represents more
evidence to confirm Darwin's conclusion that the earliest humans,
or hominids, the primate zoological family that includes all
species on the human side of the evolutionary split with
chimpanzees, arose in Africa.


     Yohannes Haile-Selaissie, a paleontologist studying for a
Ph.D. at the University of California at Berkeley, made the
recent fossil discoveries from these earliest creatures.  Working
under lead researcher Tim D. White, a Berkeley colleague, Haile-
Selaissie found a jawbone and teeth in December, 1997.  More
fossils were found, the last a tooth, uncovered in January, 2001.


     "The new fossils come from the oldest of the patches of
exposed sediment at Saitune Dora, Alayla, Aas Koma and Digiba
Dora," White said.  "These bones and teeth were difficult to find
on surfaces that are littered with stones ranging from pebbles to
boulders."


    The area where this hominid discovery took place has been
the focus of much attention in recent years.  Eleven hominid
specimens have been recovered from five late Miocene localities
within the Middle Awash region.

    The study of the Middle Awash has been ongoing since 1981
under the joint direction of White and Desmond Clark of UC
Berkeley, Giday WoldeGabriel of Los Alamos National Laboratory
and Ethiopian researchers Berhane Asfaw and Yonas Beyene.

    The researchers explain that about six million years ago,
the Middle Awash region was already a well-defined rift valley
characterized by intense earth movements, with active volcanoes
nearby.  "It is hard to imagine life would go on normally under
such hostile environmental conditions -- Ardipithecus and the
other animals inhabiting the area were real survivors,"
WoldeGabriel said.


White says that an accurate portrayal of these creatures is not
yet possible because an intact skull or limb bones are yet to be
found.  Estimates are that the bones of the skeleton and the
lower jaw are roughly the same size as a modern chimpanzee.  The
previous discovery of the 4.4-million-year-old Ardipithecus
ramidus was up to this point the oldest known hominid.


     "This is an exciting development," says Mark Weiss, program
director of physical anthropology at NSF.  "Not only are we
gaining insights into the anatomy of what may be some of our
earliest ancestors, but we are seeing a better picture of the
environment in which they lived.  I'm really looking forward to
further finds by White and his colleagues."


     The age of these newly found fossils was determined by the
Berkeley Geochronology Center by employing an argon-argon laser
heating method -- a process that determines the time elapsed
since volcanic ashes and lavas were erupted by measuring the
argon gas trapped in the rock after it cools.  "The argon dating
results were corroborated by geomagnetic polarity data, then
further confirmed by biochronological analysis of the primitive
fossil animals found with the human ancestor remains," White
explains.


     "These fossils are strong evidence that that lines leading
to chimpanzees and humans had already split well before five
million years ago," Haile-Selaissie concludes.

                              -NSF-


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