Reasons to Believe

The Case for Human Evolution Loses Some Teeth

Dental Anatomy Gives Important Clues on Hominid Growth and Development

For a little kid, losing teeth is a rite of passage. Each tooth that falls out (or gets unceremoniously yanked loose) serves as a sign that the child is growing up, as, one by one, baby teeth make way for permanent teeth.

The same is true for hominids, which are often interpreted as transitional intermediates between an ape-like creature and modern humans. Hominid tooth eruption, deposition of microanatomical structures, and tooth wear occurred at characteristic times during their growth and development and throughout adulthood. Because of the relationship between dental anatomy and life history, paleoanthroplogists study these features to gain important clues about the behavior and lifestyle of these now-extinct creatures.

Two recent research projects examined dental features of Paranthropus robustus and Neanderthals. Both studies indicate that these two hominids developed and behaved in decidedly nonhuman ways, extending the separation between the hominids and modern humans in accord with RTB’s human origins model.

RTB Human Origins Model and the Hominids

Instead of viewing these creatures as evolutionary intermediates, RTB’s biblical creation model regards the hominids found in the fossil record as animals created by God’s direct intervention. These primates 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. This allowed these animals to employ crude tools and even adopt a type of ‘culture’ much like baboons, gorillas, and chimpanzees. While the RTB model posits that the hominids were created by God’s divine fiat, they were not spiritual beings made in His image. The model reserves this status exclusively for modern humans.

The RTB’s conceptual scheme treats the hominids as analogous to, but distinct from the great apes. Because of this, the model predicts that anatomical, physiological, biochemical, and genetic similarities will exist among the hominids and modern humans to varying degrees. But since the hominids were not made in God’s image, they are expected to be clearly distinct from modern humans, particularly in their cognitive capacity, behavior, “technology,” and “culture.”

In summary, the RTB model predicts that the hominids, including Neanderthals, should be biologically and behaviorally distinguishable from modern humans.

One study examined facial features and tooth wear for 19 specimens assigned to Paranthropus robustus. This hominid lived between about 2 and 1.2 million years ago in South Africa. (Evolutionary biologists don’t think that this hominid is part of the lineage that led to modern humans. Instead they place P. robustus, along with its two sister species, P. boisei and P. aethiopicus, as an evolutionary side branch and dead end.)

The research team noted that for male specimens the most extensive dental wear correlated with fully developed adult features. Those males with underdeveloped adult characteristics showed little dental wear. This pattern was not noted for females in the sample. These observations indicate that males took a longer period of time to develop than females and imply that P. robustus displayed sexual dimorphism, with males possessing a significantly larger body size than females.

Sexual dimorphism impacts mating strategy. Primates like gorillas that display sexual dimorphism based on body size have a social organization centered on a large dominant male who mates with a harem of females. This means that Paranthropus, and by extension the other Australopithecines, employed a mating strategy similar to gorillas.

In contrast, modern humans display relatively limited sexual dimorphism. As a consequence, males and females form mating pairs.

This work indicates that the Australopithecines were biologically and behaviorally distinct from modern humans, in accord with predictions made by the RTB model. The study also widens the gap between the Australopithecines and hominids that belonged to the Homo genus. According to paleoanthropologist J. Michael Plavan:

The finding challenges a theory that early hominids had a relatively low level of sexual dimorphism, inherited from a common ancestor shared with chimpanzees…Instead, the primitive condition may have been more gorillalike, and our female ancestors may not have closed the gap until recently, perhaps in Homo erectus in the past 2 million years.

The implication: the transition in mating behavior (and the accompanying growth and development process) must have happened rapidly.

Another study examined microanatomical features of Neanderthal teeth as a way to assess the rate of growth and development for these hominids. Biological rhythms produce incremental features in the enamel and dentine throughout childhood that can be used as a record for the individual’s life history.

Earlier studies using these markers have been inconclusive about the growth and development of Neanderthals. Some studies indicate that these hominids grew into adulthood at a pace similar to that of modern humans. Other work suggests that the rate of growth and development was accelerated when compared to human beings.

The most recent study took the most-detailed and comprehensive look at the microanatomical characteristics of Neanderthal teeth. Based on this work, the researchers concluded that Neanderthals grew at a much more rapid rate than modern humans. To say it another way, a prolonged childhood and relatively slow life history appears to be unique to modern humans. And these differences in the length and pace of childhood have important consequences for social organization.

Based on this work, it appears as if Neanderthals are both biologically and behaviorally distinct from modern humans. Once again this finding comports with RTB’s human origins model. Scientific advance makes it increasingly possible to make a scientific case that human beings are distinct from the hominids in a way that harmonizes with the notion that humans are uniquely made in God’s image.

While it is commonplace for human children to put their baby teeth under a pillow in the hope that the tooth fairy will exchange it for “gold,” it’s unlikely that Neanderthal children ever went through such a ritual. They grew up too fast.

Subjects: Lucy and Other Hominids, TCM - Human Origins

Dr. Fazale Rana

In 1999, I left my position in R&D at a Fortune 500 company to join Reasons to Believe because I felt the most important thing I could do as a scientist is to communicate to skeptics and believers alike the powerful scientific evidence—evidence that is being uncovered day after day—for God’s existence and the reliability of Scripture. Read more about Dr. Fazale Rana