Wide-hipped fossil changes picture of Homo erectus

WASHINGTON (Reuters) - The fossil of a wide-hipped Homo erectus found in Ethiopia suggests females of the pre-human species swayed their hips as they walked and gave birth to relatively developed babies with big heads, researchers said on Thursday.

The finding transforms thinking about some early human ancestors and evolution and suggests that helpless babies came along relatively late in the human lineage.

"We could look at this pelvis and then, using a series of measurements, we can calculate ... how big the baby's head could be at birth," said Scott Simpson, a paleontologist at Case Western Reserve University who worked on the study.

Writing in the journal Science, Simpson and colleagues said the size and shape of the 1.2 million-year-old pelvis indicates that H. erectus females had hips wider than those of modern human females and their infants were born with heads about 30 percent larger than previously calculated.

"What this means is the offspring were not as helpless as a modern human," he said in a telephone interview.

"It is not coming out walking and talking. But it was probably capable of more advanced behavior at a younger age like grasping, like sitting up ... than we would see in a modern human."

An extended childhood is a particularly human characteristic. Helpless babies require intensive care, not only from the mothers but from an extended group, which may have spurred the development of human society and culture.

Homo erectus, Latin for "upright man," arose in Africa 1.8 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.

Scientists did not know much about what its body would have looked like until the discovery of "Turkana Boy," an adolescent H. erectus whose bones were discovered in 1984.

His slim-hipped build led researchers to believe that H. erectus gave birth to small-headed babies that would have required a great deal of care in early life, much like modern human infants.

But Simpson said Turkana boy's pelvis was damaged and the restoration of a near-complete female pelvis from Gona, Ethiopia, changes this picture.

"This H. erectus would have even wider hips (than modern women)," Simpson said.

One main difference between human males and females is hip width, which makes women sway as they walk and which allows men to run and walk more efficiently.

"The reason women do have that sway is their hips are a little further apart," Simpson said. "She would have had a good one."

(Editing by Alan Elsner)