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The oldest and most efficient female humanoid pelvis discovered in Ethiopia
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Pelvis Dated To 1.2 Million Years Ago Shows Ancestors May Have Been Born With Big Heads
Science Daily (based on a report provided by Indiana University) | November 15, 2008
A reconstruction of the 1.2 million-year-old pelvis discovered in 2001 in the Gona Study Area at Afar, Ethiopia, that has led researchers to speculate early man was better equipped than first thought to produce larger-brained babies. The actual fossils remain in Ethiopia. (Credit: Scott W. Simpson, Case Western Reserve University)
Discovery of the most intact female pelvis of Homo erectus may cause scientists to reevaluate how early humans evolved to successfully birth larger-brained babies.
"This is the most complete female Homo erectus pelvis ever found from this time period," said Indiana University Bloomington paleoanthropologist Sileshi Semaw. "This discovery gives us more accurate information about the Homo erectus female pelvic inlet and therefore the size of their newborns."
A reconstruction of the 1.2 million-year-old pelvis discovered in 2001 in the Gona Study Area at Afar, Ethiopia, that has led researchers to speculate early man was better equipped than first thought to produce larger-brained babies. The actual fossils remain in Ethiopia.
The discovery will be published in Science this week (Nov. 14) by Semaw, leader of the Gona Project in Ethiopia, where the fossil pelvis was discovered with a group of six other scientists that includes IU Department of Geosciences graduate student Melanie Everett.
Reconstructing pelvis bone fragments from the 1.2 million-year-old adult female, Semaw and his co-workers determined the early ancestor's birth canal was more than 30 percent larger than earlier estimates based on a 1.5-million-year-old juvenile male pelvis found in Kenya. The new female fragments were discovered in the Gona Study Area in Afar, Ethiopia, in 2001 and excavation was completed in 2003.
Scientists also were intrigued by other unique attributes of the specimen, such as its shorter stature and broader body shape more likely seen in hominids adapted to temperate climates, rather than the tall and narrow body believed to have been efficient for endurance running.
Early humans became taller and narrower over time, scientists believe, partly due to long distance running and to help them maintain a constant body temperature. One consequence, however, is that a narrower pelvis would have been less accommodating to producing larger-brained offspring.
But rather than a tall, narrow hominid with the expected slight pelvic region, Semaw and the Gona researchers found evidence of a hominid ready to produce offspring with a much larger brain size.
"The female Homo erectus pelvic anatomy is basically unknown," Semaw said. "And as far as the fossil pelvis of ancestral hominids goes, all we've had is Lucy (dated at 3.2 million years and also found in Ethiopia), and she is very much farther back in time from modern humans."
Scientists studying early man predominantly find fragments of craniums and dental remains, while fossil bones from the neck down are rarely discovered. Even more difficult to verify are Homo erectus fossil bones that can be identified as those belonging to a female.
Scientists had thought early adult Homo erectus females, because of the assumed small birth canal, would produce offspring with only a limited neonatal brain size. These young would have then experienced rapid brain growth while still developmentally immature, leading researchers to envision a scenario of maternal involvement and child-rearing on par with that of modern humans. But those theories had been based upon extrapolations from the existing male skeleton from Kenya.
"This find will give us far more accurate information," Semaw said. Semaw is also a research scientist at the Stone Age Institute, a research center near Bloomington dedicated to the study of early human evolution and culture. It is affiliated with Indiana University's CRAFT, the Center for Research into the Anthropological Foundations of Technology.
Gona has turned out to be a productive dig site for Semaw. In 1997 Semaw and colleagues reported the oldest known stone tools used by ancestral humans. Then in 2004 he coauthored a paper summarizing Gona's geological properties and the site's cornucopia of hominid fossils spanning several million years. At the time, Science gave the article an "Editor's Choice" recognition. In 2005 he and colleagues published an article in Nature announcing the discovery of Ardipithecus ramidus, one of the earliest ancestral hominids, dating between 4.3 and 4.5 million years ago.
Scott Simpson (Case Western Reserve University School of Medicine and the Cleveland Museum of Natural History), Jay Quade (University of Arizona), Naomi Levin (University of Utah), Robert Butler (University of Portland) and Guillaume Dupont-Nivet (Utrecht University, Netherlands) also contributed to the report. Support for the research was provided by the Leakey Foundation, the National Science Foundation, the National Geographic Society and the Wenner-Gren Foundation.
The authors thank Ethiopia's Authority for Research and Conservation of Cultural Heritage and the National Museum of Ethiopia for research permits and support.
Adapted from materials provided by Indiana University.
Wide-hipped homo changes picture of Homo erectus
By Maggie Fox, Health and Science Editor
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)