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April 30, 2010

Pelvic-bone Comparison

Three sets of pelvic bones (both a side view and top view) are shown, along with the approximate size of full-term fetus they could handle. On the left is the pelvis and baby of "Lucy," the Australopithecus afarensis from 3.2 million years ago. In the middle is the newly discovered pelvis of 1.2 million year old Homo erectus. And on the right is the pelvis and baby of a modern day female human being, or Homo sapiens. Homo erectus was previously thought to produce babies with relatively small brain capacity. However the discovery of the pictured pelvis has shown that they were actually capable of birthing babies with a cranial circumference very close to the lower end of the range of our own species. The Homo erectus shown could have produced a baby with a cranial circumference of 318 mm, while modern day babies vary from 320 to 370 mm.

This image accompanied NSF press release, "Discovery Questions Intelligence of Human Ancestor."

Credit: Zina Deretsky, National Science Foundation

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