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The pursuit of an older female

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LANL geologist provides chronology for new discoveries in human ancestry

By Roger Snodgrass

What may be one of the hottest science stories of the year involves a well-known local scientist, who will be featured in a documentary on the Discovery Channel (Channel 51 locally) at 7 p.m.

Of special interest is the role of a Los Alamos geologist, Giday WoldeGabriel, co-director of an ongoing investigation in the Afar Rift of Ethiopia that has uncovered the remains of a new human ancestor.

“This time it is very old, 4.4 million years,” said WoldeGabriel in an interview Thursday.

 “It’s a partial skeleton, unlike the small fragmentary piece discovered in the past.”

The story has been front-page, above-the-fold material for major newspapers in recent days, featured in scientific journals and popular magazines and is already cropping up on television.

A high point, so far, was a special News Focus section in the Oct. 2 issue of the journal Science, launched with a press conference and an elaborate background document. At least two books are planned.

The original clue, a single tooth, was unearthed in 1992. Two years later, a hand bone of the skeleton of the newly identified creature was found.

Over the years the scientific team has collected and analyzed a large assemblage of additional documentation that includes the partial skeleton of Ardipithecus ramidus, thought to be representative of an early human forebear.

Apparently arriving not long after human ancestors came out of the trees and started living on the ground. Ardipithecus ramidus means “root of the ground ape,” although the scientists note that this creature is no longer an ape, but rather advanced along the branch from which humans would descend.

A team of more than 47 different scientists from 10 countries have contributed to the project, authoring 11 scientific papers among them.

WoldeGabriel, who works at Los Alamos National Laboratory most of the year, headed the field geology. His ability to interpret the stratigraphic geological markers has enabled the project to pinpoint the timeframe, which he has calculated is within 10,000 to 100,000 years of 4.4 million years ago.

“Ardi,” as she is called, was a large female of her kind, unlike the well-known ancestral human, Lucy, who was small for her time and younger than “Ardi” by 1.2 million years.

“It’s a closely related jigsaw puzzle,” WoldeGabriel said. “That’s why it’s so special, compared with anything before.”

With such a variety of evidence from a very narrow time period, the scientists believe they can clearly describe the people and their environment, including not only the hominids, but a whole range of other animals from large vertebrates like elephants, monkeys and hyenas; to small vertebrates like snails, as well as birds, plants and seeds.

Why this discovery has caused such a sensation, WoldeGabriel believes, is because this creature is the closest scientists have found to the “last common ancestor” between man and chimpanzees.

Paleontologists, who study the ancient past, have rejected the term “missing link” in favor of the more accurate term, “last common ancestor,” because individual fossils can hardly be links, when they represent only a sliver of a the population of a species at a particular time.

“We don’t know when the split happened,” WoldeGabriel said, “but at least there is so much evidence here that people can talk about what the common ancestor was.”

During a recent taping with Paula Zahn of CBS, WoldeGabriel said he was asked if we were going to find the common ancestor during our lifetime.

“I told her that is our goal,” he said. “We have the geology and we’ll keep on looking.”

The scientists believe any remains from that creature will be more than 6 million years old, because they have some evidence from 5.8 million years of a hominid that has already evolved along the human line.

“So a geologic package that’s between 6 and 10 million years old is my target,” he said. “Anything we find is going to be related to one of these animals, so we can say how far it has evolved within that time period.”

Another driver for the interest in “Ardi” is the coincidence this year, with the 200th birthday of Charles Darwin, the father of the concept of “common ancestors,” and the 150th anniversary of the publication of his book, “The Origin of Species.”

A Gallup Poll conducted for Darwin’s birthday earlier this year found that only 39 percent of Americans believe in evolution.