Prehistoric pelvis hints at how humans evolved to have large-brained babies

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Washington, Nov 14 : A prehistoric pelvis of Homo erectus discovered in Ethiopia could help researchers answer questions about how early humans developed to successfully give birth to larger-brained babies, a study released Thursday has said.

The reconstruction of the pelvis bone fragments from the 1.2 million-year-old adult female discovered in 2001 in the Gona Study Area at Afar, Ethiopia, has led researchers to speculate early man was better equipped than first thought to produce larger-brained babies.

Semaw, leader of the Gona Project in Ethiopia, and six others discovered the actual fossils, which still remain in Ethiopia.

"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," the expert added.

By reconstructing the pelvis bone fragments, the researchers found out that 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.

There were other unique attributes of the specimen that intrigued the scientists, including 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.

It sis believed that early humans became taller and narrower over time, in part due to long distance running and to help them maintain a constant body temperature.

However, one consequence is that a narrower pelvis would have been less accommodating to producing larger-brained offspring.

But instead of a tall, narrow hominid with the expected slight pelvic region, evidence has been found of a hominid ready to produce offspring with a much larger brain size.

It was believed that early adult Homo erectus females, because of the assumed small birth canal, would produce offspring with only a limited neonatal brain size and would have then experienced rapid brain growth while still developmentally immature.

That's what led the researchers to envision a scenario of maternal involvement and child-rearing on par with that of modern humans.

However, the theories were mainly based on extrapolations from the existing male skeleton from Kenya.

But the new discovery has completely changed the picture.

"This find will give us far more accurate information," said Semaw.

The study will be published in Science.

ANI

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