LANL geologist dates human origins

The pieces of the evolutionary record, although spread across chasms of time, were found within walking distance of each other in what is now a deserted landscape of the Middle Awash valley in the Afar Region of Ethiopia.

Giday WoldeGabriel, a geologist from Los Alamos National Laboratory and the co-director of the Middle Awash project, has been associated with the team of international scientists since 1989. The project has been highly successful over the years in discovering material remains that shed light on the hominid period of human development, from the time the human family of primates diverged from chimpanzees.

As documented in Nature magazine this week, the team has now identified fossils chronologically between more ape-like creatures known as Ardipithecus, dated 4.4-7 million years ago, and the ape-man genus Australopithecus, the family that flourished after about 3.5 million years ago and includes the famous "Lucy" ancestor. The new fossils, found at two sites, Aramis and Asa Issie, are thought to be a more primitive species of that same family, but about 300,000 years earlier, called Australopithecus anamensis.

"It is fair to say that some species of Ardipithecus gave rise to Australopithecus," said Tim White, based on the find, in an announcement Wednesday. White is one of the team leaders and a professor of biology at UC Berkeley.

A background paper prepared by the Human Evolution Research Center at UC Berkeley, included WoldeGabriel's description of the habitat during that time.

"The abundance of monkeys, kudus, and other mammals, and petrified wood found both at Aramis and Asa Issie, shows that a closed, wooded habitat type persisted over a long period in this part of the Afar and was favored by early hominids between 4 and 6 million years ago," he said.

WoldeGabriel typically spends about a month each year in and around the Middle Awash region of Ethiopia.

In an intervew Friday, he said one reason so many hominids are found in East Africa is because an ice-age had enveloped the northern and southern hemispheres.

In the Great Rift Valley, with mountains on both sides moderating the climate, there was enough water and animals could migrate up and down the continent.

What is today a dusty stone-age, semi-arid environment, was much more hospitable.

"It was practically a garden of Eden," he said.

Today, the geological dynamics have pushed up old layers, exposing what WoldeGabriel called, "their buried treasures."

He said, "It's like a gold mine. You find a nugget here and there, golden nuggets of human ancestry. We've found more than half the known human ancestors in this one region called the Middle Awash."

During a period of unfriendly weather conditions in 1997, WoldeGabriel found himself stranded for a time in a low-lying area known as Bouri, where he and coworkers found a remarkably revealing layer-cake of the human family tree.

In a package of younger rocks, they found a "more or less modern" hominid dated to 160,000 years ago. Below that, they found a skull of Homo erectus, a hominid branch from a million years ago, or about 600,000 years before that branch died out.

And below that site, they found at the same a new species called Australopithecus gahri.

"Gahri" means surprise in the local Afar language.

Dated at about 2.5 million years ago, WoldeGabriel said a closely related assemblage of archeological material included "a lot of bones, " some of which showed "cutting and crushing for bone marrow extraction and cutting meat."

The significance of the find was that it was the first indication of the use of stone tools, dated at 2.5 million years ago.

In analyzing the material at Bouri, as well as the new material announced this week WoldeGabriel worked with an old college friend, Berhane Asfaw, another long-time team member who lives in Addis Ababa and was his original connection to the Middle Awash group.

WoldeGabriel was born in a rural area of Northern Ethiopia.

If it hadn't been for an American Lutheran church that "opened a school in the middle of nowhere," he said. "There wouldn't have been any chance to go to government schools."

He was able to complete his college and graduate work at the University of Addis Ababa, and then to Case Western Reserve University in Ohio where he took a Ph.D.

Currently involved in geological investigations at the Nevada Test Site and at LANL for his day job, WoldeGabriel answers profound questions of human origins in his spare time. He is partly funded by the Institute of Geophysics and Planetary Physics, a University of California organization.

He said his geological work differs from the paleontologists.

"They do digs and find every bone. I'm always by myself, five or 10 miles away, following a layer or a time marker of volcanic ash, trying to see what's below or what's above," he said. "I have a good understanding of what's going on, but if you were to pick a bone and ask me what it is, I don't have a clue."

He said he focuses on what he's good at.

"How old things are, that's my main responsibility," he said.