NSF PR 99-31 - April 27, 1999
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A "Missing Link" Fossil Adds "Foliage" to the Early
Human Ancestor Family Tree
East African paleo-anthropological sites have yielded
2.5- million-year-old fossils of a possible direct
human ancestor. "These fossils are providing exciting
new evidence about the long sought evolutionary connection
between species of early hominids, like Australopithecus,
and the genus Homo," said National Science Foundation
(NSF) Physical Anthropology Program Director Mark
L. Weiss.
The cranial, leg, and arm bone fossils of this newly
discovered species were unearthed in Ethiopia by a
team of scientists led by NSF-supported anthropologist
Tim White of the University of California-Berkeley
and Berhane Asfaw of Ethiopia, and are publicized
in the April 23 issue of Science magazine. Significantly,
the femur is elongated-a million years before hominid
fossil evidence shows forearm shortening-which, together
with shortened forearm, creates the familiar modern
human limb proportions.
Similar-age animal fossils discovered in the same
area, the Middle Awash study area in the Afar desert,
indicate that the meat and bone marrow of large mammals
(antelopes and horses, specifically) were obtained
with the world's earliest stone tool technology, according
to a companion article in Science. White cautioned
that "we cannot yet conclusively link the new species
with the butchery or the more modern limb proportions."
Both sets of fossils were dated using the argon-argon
radioisotope method as well as biochronology and paleomagnetism.
The same research team had discovered the earliest-known
hominid, the 4.4-million-year-old Ardipithecus, at
the nearby Aramis site in 1992.
These fossil finds are significant for several reasons,
according to the discoverers. "The hominid fossils
may allow us to add a new member to the human evolutionary
family tree," said Weiss, "and the evidence regarding
the use of stone tools in food processing indicates
an early reliance on meat in hominid diet. This adaptation
would have allowed them to venture into new habitats
and ultimately into new continents."
According to the discoverers, the new Ethiopian hominid
fossils, named Australopithecus garhi, help fill a
serious void in the east African record of human origins
that spans a duration of between 2 and 3 million years
ago. This void has made it impossible to settle scientifically
the relationship between the 1.8-million-year-old
Homo habilis and earlier ape-like Australopithecus
africanus.
Increasingly, the focus on African early hominid fossil
wealth has centered on Ethiopian sites in contrast
to the last few decades' focus on better-known productive
sites in Tanzania, Kenya and elsewhere. "With the
publication of these new results, and with a record
spanning five million years, Ethiopia's Middle Awash
has become the world's most important single site
for studying human origins and evolution," said White.
The research in the Middle Awash area is supported
mainly by the National Science Foundation. Additional
support comes from the Institute of Geophysics and
Planetary Physics of the University of California's
Los Alamos National Laboratory and several other institutions
mentioned in the published Science articles. The international
research team includes archaeologists, geologists
and paleontologists from diverse institutions in 13
countries.
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