Did the lateral enamel of Neandertal anterior teeth grow differently from that of modern humans?

The formation of lateral enamel in Neandertal anterior teeth has been the subject of recent studies. When compared to the anterior teeth of modern humans from diverse regions (Point Hope, Alaska; Newcastle upon Tyne, England; southern Africa), Neandertal anterior teeth appear to fall within the modern human range of variation for lateral enamel formation time. However, the lateral enamel growth curves of Neandertals are more linear than those of these modern human samples. Other researchers have found that the lateral enamel growth curves of Neandertals are more linear than those of Upper Paleolithic and Mesolithic modern humans as well. The statistical significance of this apparent difference between Neandertal and modern human lateral enamel growth curves is analyzed here. The more linear Neandertal enamel growth curves result from the smaller percentage of total perikymata located in the cervical halves of their teeth. The percentage of total perikymata in the cervical halves of teeth is therefore compared between the Neandertal sample (n=56 teeth) and each modern human population sample: Inuit (n=65 teeth), southern African (n=114 teeth), and northern European (n=115 teeth). There are 18 such comparisons (6 tooth types, Neandertals vs. each of the three modern human populations). Eighteen additional comparisons are made among the modern human population samples. Statistically significant differences are found for 16 of the 18 Neandertal vs. modern human comparisons but for only two of the 18 modern human comparisons. Statistical analyses repeated for subsamples of less worn teeth show a similar pattern. Because surface curvature is thought to affect perikymata spacing, we also conducted measurements to assess surface curvature in thirty teeth. Our analysis shows that surface curvature is not a factor in this lateral enamel growth difference between Neandertals and modern humans.