The uniquely human capacity of surviving by using our brains, not our brawn, began developing a million or so years before the time scientists had previously estimated, according to research assisted by fossil and soil dating expertise at the University of Utah.

The notion comes not from skull size but from the nearly intact pelvic bone of a female Homo erectus discovered in Ethiopia that strongly suggests the females of the pre-human species just before Homo sapiens had wide hips and gave birth to infants with heads one-third larger than researchers had believed.

In an article published in today's edition of the journal Science, researchers write that calculations based on the size and shape of the 1.2 million-year-old pelvis indicate that H. erectus females had hips wider than those of modern human females and were not the long, lean, built-for-speed body types scientists had believed.

Because earlier finds indicated the species appeared to have a small pelvis, scientists thought its babies were born with small brains that grew rapidly after birth, the study said. The fossil, the first documented complete Homo erectus female pelvis, was found in 2001 just a few kilometers east of where another famous, much older and much more complete female skeleton, "Lucy," was found.

Those remains include many more bones and are the only known female remains of the species Australopithecus afarensis found in 1974 and believed to be 3.2 million years old.

The H. erectus fossil pelvis could well be as important to understanding evolution during that era, said Naomi Levin, co-author and Ph.D. graduate in the Geology and Geophysics Department at the U.

H. erectus will now be viewed as a species capable of having offspring that required significant amounts of maternal care, much like modern human babies, she said.

"Our environmental evidence, mostly from stable isotopic studies, suggest that although the environment at Gona was quite arid during the time that this individual lived, this individual was not long and lean."

The find has already countered current thinking, which was a partial picture at best because the only other near-complete H. erectus pelvis is male, Levin added.

That pelvis, part of the Nariokotome Boy skeleton, was announced in 1985 by then-principal scientist Frank Brown, currently dean of the College of Mines and Earth Sciences at the U. and former advisor to Levin who is now at the California Institute of Technology. A replica of this skeleton is on display in the Browning Building at the U.

Levin, who was at the U. for five years and finished her doctorate earlier this year, has been working on the Gona project since 2001 — the season that the female pelvis fossil was discovered — and will return to the field next month. She specializes in research using soil sediments and isotope geochemistry for reconstructing past environments.

The fossil fragments were found in February by Sileshi Semaw, a researcher at the Stone Age Institute in Bloomington, Ind., who led the excavation. Semaw helped find the world's oldest known stone tools — hand axes and cleavers — in 1999 at a nearby site.

Most Homo erectus remains are fossils of teeth and skulls showing that the pre-humans were already developing larger, more human-like brains, he said.

More human-like brains indicate helpless babies who require intensive care, not only from the mothers but from an extended group, which in turn indicates possible development of human society and culture.

Homo erectus, Latin for "upright man," arose in Africa 1.8 million to 2 million years ago, migrating to Asia and Europe before becoming extinct about half a million years ago. Experts agree it was likely a direct ancestor of modern humans.

Levin said her research and the project are extensions of research under way in the region by Brown and U. geologist Thure Cerling.

"The more fossils that are found, the more we can use the environmental data that I produce to help understand how environmental change shaped human evolution," she said. "We find new exciting fossils every field season at Gona, and surely there are more to come."