Find May Be Oldest Humans

LANL Geologist Reshapes History

A Los Alamos geologist working largely in his spare time has helped rewrite the history of human evolution.

In a paper being published today, Giday WoldeGabriel and his colleagues are announcing the discovery of fossils they believe are the earliest known members of our own species, a group that wandered a lake shore in eastern Africa 160,000 years ago.

The find is the latest discovery by a scientific team working in east Africa’s great rift valleys. They found the fossils in 1997, but it was a long and complicated struggle to pin down their age, WoldeGabriel, a Los Alamos National Laboratory geologist, said.

WoldeGabriel, 48, is co-leader of a research team that has worked over the past decade in an area that is increasingly seen as the cradle of human evolution.

There, the first humans seem to have evolved from more ape-like ancestors.

In an interview this week, the Ethiopian-born WoldeGabriel said he takes particular pride in the fact that his group has for many years been the only scientific team led by indigenous Africans to be studying our ancient African ancestors.

In a series of papers over the last four years in Science and Nature — the world’s most prestigious scientific journals — the team’s members have reported on a dramatic series of ancestral human fossils, reshuffling the branches on our family tree.

Their most recent discovery is being published today in Nature.

For WoldeGabriel, the work has required spending hours of his own time, beyond his regular work at Los Alamos. Most days, WoldeGabriel works in the lab’s environmental programs, studying the geology of the Los Alamos area and the Nevada Test Site, where U.S. nuclear weapons tests were once conducted.

The University of California funds annual research trips to Ethiopia. But the work needed after he returns to analyze what the team has found and write up the results is done on his own time, he said.

The team’s previous finds in the area include Ardipithecus, a 4- million- to 5-million-year-old species that is the earliest ape- like hominid, and Australopithecus garhi, the 2.5 million-year-old first tool-using hominid.

The group’s most recent fossil discovery is the closest to home.

Led by University of California, Berkeley, researcher Tim White, the team’s anthropologists concluded that the three skulls, two adults and a child, bore clear characteristics of modern Homo sapiens — modern humans.

It was up to WoldeGabriel and the other geologists on the team to figure out how old they were.

Using layers of volcanic ash found above and below the fossils, the scientists pinned down the age to about 160,000 years.

That made the find remarkable.

Before the discovery, the oldest known fossils of modern humans dated from 115,000 years ago, from caves in Israel.

The time, 160,000 years ago, is recent in geologic terms. Continents move, and mountains form and erode away, on time scales of hundreds of millions to billions of years.

Despite being recent, however, the Earth looked very different. An ice age gripped the planet. To the north, much of Europe was covered in glaciers.

According to WoldeGabriel, the Herto humans, named after a modern village near where the fossils were found, lived along the margins of a great lake.

Catfish lived in the lake, and hippos and crocodiles prowled its shores.

Based on few and fragmentary fossils, the study of human ancestors is a controversial business.

For example, Chinese scientists claim to have found 200,000-year- old Homo sapien fossils, but other scientists believe it is really an older relative, not one of us, according to Wes Niewoehner, an anthropologist at California State University, San Bernardino.

By pushing back the evolution of modern humans to at least 160,000 years, and the place to Africa, the find by White, WoldeGabriel and their colleagues adds support to the “out of Africa” theory of human origins, according to Chris Stringer, an anthropologist at The Natural History Museum in London.

The idea is that modern humans first evolved in eastern Africa, then spread rapidly across the world, displacing Neanderthals and other hominids that preceded them.

Studies of modern human genetic diversity point to an African origin, though some scientists still support a competing idea — that pre-human ancestors spread out of Africa, and that modern humans then arose in a number of separate groups.

Writing an accompanying piece in Nature, Stringer called the skulls “some of the most significant discoveries of early Homo sapiens so far,” providing a key link between African origins and later fossils.