Focusing on the Pelvis

Focusing on the Pelvis

New Discovery Indicates Homo erectus Grew and Developed like an Ape, Not a Modern Human

Elvis Presley earned the nickname “Elvis the Pelvis” after his first appearance on the Ed Sullivan Show. Following that performance, TV executives and the show’s producers, concerned about Elvis’s gyrations, instructed cameramen to film Elvis only from the waist up. Millions of disappointed fans weren’t able to see Elvis’ patented moves and the controversy drew even more attention to his midsection.

Similarly, paleoanthropologists have been frustrated their attempts to study the pelvises of female Homo erectus specimens. Even though H. erectus has been known from the fossil record for over 100 years and a significant number of fossil finds exist, there are scant remains of this creature’s postcranial skeleton, including the pelvis.

Paleoanthropologists want to examine the pelvis of female H. erectus because it will give them important clues about the growth and development of humans versus that of apes. Fortunately, a recent discovery of a nearly complete female H. erectus pelvis has brought an end to the frustration and with it a few surprising answers.*

Brains and Brawn in Humans

One of the defining features of modern humans is large brain size relative to body mass. (This ratio is called the encephalization quotient.) Large brains make it impossible for brain growth to take place entirely within the womb, because the birth canal can’t accommodate a large head. This difficulty means that a substantial amount of brain growth happens after birth. At the time of birth, the brain size of human infants is about 25% of the adult brain. By the time a human child reaches its first birthday, its brain is about half the size of an adult brain. It’s not until the child reaches six years of age that its brain is fully grown.

Due to the amount of resources required to allow the human brain to grow, the growth of its body is delayed. Through the teenage years, the body continues to grow while the brain carries on developing, though it doesn’t increase in size. By comparison, when a chimpanzee is born, its brain is already 40% the size of the adult brain; it reaches 80% by the time the chimp turns one year old.

Brains and Brawn in the Hominids

To understand the origin of human development, anthropologists turn to the hominid fossil record for clues. Many scientists regard these creatures as transitional intermediates linking an alleged ape-like ancestor to modern humans.

Study of australopithecine pelvises indicates that their bodies were modeled to accommodate bipedalism, but not the birth of large-brained infants. This makes sense, since the brain size of these creatures is just a little larger than the brain size of chimpanzees.

Also of interest to anthropologists is H. erectus. Evolutionary biologists believe this hominid represents the midpoint in the transition from an ape-like creature and modern humans. This hominid also displayed a form of bipedalism very similar to modern humans and it had a larger brain than those of the australopithecines.

The “Turkana Boy” remains, dating to about 1.8 million years in age, is one of the few H. erectus finds that possesses a complete pelvis. This hominid died when it was between 8 to 10 years of age. Its pelvis was rather narrow. Without the pelvis of a female available at the time, the researchers applied observations taken from Turkana Boy about pelvis size to female, as well as male, H. erectus. On this basis anthropologists concluded that its growth and development was much more human-like than ape-like. With a narrow pelvis, it would be difficult to give birth to hominids with the relatively large brains that H. erectus possessed.

This interpretation stands in sharp contrast to other studies, including analysis of the microanatomy of teeth and the brain size estimates of the “Mojokerto Child”, indicating that the growth and development of H. erectus was more ape-like. (For a detailed discussion of these studies see Who Was Adam?)

The Discovery and Analysis of a Female Pelvis

Anthropologists have just reported on an analysis of the first female H. erectus pelvis. The remains, recovered in Ethiopia, date between 0.9 and 1.4 million years in age. To their surprise, this pelvis was much wider than that of the male H. erectus and could readily accommodate the birth of a relatively large-brained infant.

The discovery of this obstetrically spacious pelvis means that H. erectus offspring didn’t require a prolonged period of brain growth outside the womb. In other words, their development was much more ape-like than human-like.

H. erectus and the RTB Human Origins Creation Model

This new insight into H. erectus fits well within the RTB creation model for humanity’s origin. According to this scientific theory, hominids, like H. erectus, were animals created by God’s direct intervention. These creatures existed for a time and then went extinct. RTB’s model considers the hominids to be remarkable creatures that walked erect and possessed some level of limited intelligence and emotional capacity. While the RTB model posits that the hominids were created by God’s divine fiat, they were not spiritual beings, made in His image. RTB reserves this status exclusively for modern humans.

The RTB model predicts that the hominids, including H. erectus, should be biologically and behaviorally distinct from modern humans. Clearly, this is the case from a biological standpoint. The new insight into the rate and pattern of H. erectus growth and development fits well within this framework. Now that’s something to get all shook up about.

*This study made science news headlines when first published. I discussed the scientific and biblical implications of this research on the November 19, 2008 edition of our podcast, RTB’s Science News Flash. This podcast offers a unique Christian perspective on headline-grabbing discoveries. A free subscription is available through iTunes.