A story from the Salt Lake Tribune sheds more light on the discovery of the Gona pelvis:
A skull might say much about an ancient hominid's brain, but no skeletal structure reveals more than the pelvis. That's why a complete specimen from an estimated 1.3-million-year-old female Homo erectus - the first known to science - has paleo-archeologists rethinking what they know about this early human ancestor.
University of Utah geologist Naomi Levin helped date the early Pleistocene fossil, whose large girth indicates H. erectus gave birth to babies with brains not much smaller than those of modern human babies, according to a study published today in the journal Science. Their brains were nearly 40 percent the size of an adult brain, indicating a greater maturity at birth. (Modern newborns' brains are 27 percent their adult size.)
This suggests a more "hit the ground running" evolutionary pattern with less neonatal and adolescent child-rearing and it is possible that Homo erectus brains reached their maximum size earlier than modern human brains do.