By Dr. Virgil Robertson
The arch in the small of your lower back is known as the “lumbar lordosis” and it plays an important role in allowing humans to stand upright and walk on two feet. If you’ve ever seen a pregnant woman negotiating her way down the aisle of a supermarket, you’ve surely noticed that the bigger the belly, the more the mother-to-be has to arch backward to keep her balance. Recently, researchers from Harvard University and the University of Texas examined this biomechanical phenomenon and made some fascinating discoveries, which were reported in the December 2007 edition of Nature.
As it turns out, the spines of men and women are not created equal. In fact, it now appears that women have been designed with specific anatomical features that enable them to safely carry the large asymmetric loads associated with pregnancy. Specifically, the research team headed by anthropologist Dr. Katherine Whitcome found that the lumbar spine of human females differs significantly from that of males. The female spine possesses an additional wedge-shaped vertebra, which substantially increases lordotic curvature in women (three wedge-shaped lumbar vertebrae in women vs. two wedge-shaped lumbar vertebrae in men). This feature allows expectant mothers to comfortably assume more extended (lordotic) postures during pregnancy. Additionally, the researchers found that the lumbar zygoapophyseal joint surfaces of women are proportionally larger and more coronally oriented than corresponding posterior joint structures in men. This distinctively female spinal configuration provides a more stable base for posterior weight bearing (hyperlordosis) and helps prevent anterolisthesis (fracture and forward slipping) of the lumbar vertebrae in pregnant women. As pregnancy proceeds and the fetus grows larger, mom simply leans back a little further (up to 28°) to balance the center of gravity over her hips—it’s a simple yet ingenious biomechanical system!
These new research findings indicate that women are particularly well equipped to safely bear the heavy anterior loads that come with pregnancy. Without these anatomical design features, pregnant women would have great difficulty balancing their unborn bundles of joy, and would be much more susceptible to myoligamentous (muscular) injuries and vertebral fractures during the third trimester of gestation.
The research team also reports that the spines of extinct hominid species (australopithecines) possessed the same kind of anatomical features and dimorphic disparities found in humans. The identification of anatomic features and biomechanical systems uniquely common to bipedal primates is not surprising. Previous authors have identified numerous anatomical and physiological characteristics in bipeds that differ from those found in quadrupeds. While the authors of this new study interpret their findings in terms of an evolutionary framework, it should be noted that these findings are, likewise, fully consistent with the predictions of RTB’s Testable Creation Model. In fact, explaining why the unique features of bipedalism appear suddenly in the hominid fossil record some seven million years ago (in the absence of transitional intermediate forms), has proven to be a substantial challenge for evolutionary biologists.
When considering the abundance of elegantly engineered biomechanical systems found in the human body, it’s hard not to be impressed by the obvious hallmarks of design. To quote British physicist Paul Davies, “The impression of design is overwhelming.”
These latest research findings fall into a long line of evidences that provide support for the existence of an Intelligent Designer. The generation of such exquisitely engineered biosystems is simply beyond the scope and capability of random mutation and natural selection.
For more on the emergence of bipedalism see Who Was Adam?