The work has required piecing together clues for over 16 years. And now Tim White, a scientist at the University of California, Berkeley, has finished the puzzle.

White led the project that discovered the earliest-known human ancestor on the primate family tree. Scientists working in Ethiopia released new findings Thursday on the 4.4 million-year-old hominid Ardipithecus ramidus, nicknamed ‘Ardi.’

The first part of the female skeleton, Ardi’s single upper molar, was discovered in the Afar Rift, Ethiopia, in 1992, 11 years after their initial research began. This began a skeletal recovery process until 2008. After the final field investigations were conducted, scientists had found a partial skeleton that was composed of more than 125 pieces of bones.

‘This is not an ordinary fossil. It’s not a chimp. It’s not a human. It shows us what we used to be,’ White said in the project literature.

Ardi replaces Lucy, a 3.2 million-year-old Australopithecus afarensis, as the oldest link in the evolutionary chain between humans and primates. The skeleton introduces new information on the separation of chimpanzees and hominids, the taxonomic family that includes humans and primates.

White worked on a team of six other researchers from facilities such as Los Alamos National Laboratory Research Library and the Rift Valley Research Service.

White’s team was not the only group working on the excavation. Forty-seven different scientists from 10 different countries have participated in the excavation since 1992. The scientists produced 11 scientific papers detailing Ardi’s discovery.

The partial skeleton does not represent a ‘missing link’ between humans and apes, however. Scientists discarded the term because it doesn’t fit with Darwin’s theory of evolution, according to project literature.

Ardi’s full name, which literally translates to ‘root of the ground ape,’ puts her in a specific place in human evolution. The fossil skeleton reveals how an ancestor to early humanoids behaved.Ardi’s primitive ape or monkey-like features indicate she was capable of climbing trees, and more evolved features indicate she was also capable of walking on two feet.

Melinda Smith, an assistant professor of ecology and evolutionary biology at Yale University, said the fossils are important in following the development of the human species. Smith will speak at SU as a part of the Department of Biology’s annual lecture series in December.

Accumulated sediments in a flood-prone area of Ethiopia have resulted in a high concentration of fossils. Lucy was found in the country in 1974.These new fossils were found in the Aramis area of Ethiopia’s Afar Rift, according to project literature.

The area’s volcanic rock allowed for a dating method based on the last eruption of volcanic ash or lava flow, which allowed scientists to estimate an age of the fossils.

‘Because (the two skeletons) were sandwiched between two volcanic horizons with virtually indistinguishable dates, the thousands of fossils collected at Aramis are among the best calibrated in the world, at 4.4 million years ago,’ said Paul Renne, project geochronologist from Berkeley Geochronology Center, in the project literature.

dkmcbrid@syr.edu

Published on October 6, 2009 at 12:00 pm

Contact Dara: dkmcbrid@syr.edu | @daramcbride