Chronology of linear enamel hypoplasia formation in the Krapina Neanderthals

Abstract

During childhood, systemic physiological stresses such as illness, disease, and malnutrition can disrupt the growth of dental enamel. These disruptions are often recorded in the form of linear enamel hypoplasia (LEH). Many researchers have analyzed the frequency and timing of LEH formation in Neanderthal populations as they relate to ideas about Neanderthal living conditions, nutrition, and foraging efficiency. Previous age estimates for Neanderthal LEH were largely based upon modern human dental growth standards. However, recent studies provide a more complete picture of Neanderthal tooth formation. We use data from these studies to create enamel growth charts for four Neanderthal anterior tooth types (upper central and lateral incisors, upper and lower canines) analogous to those created for modern humans by Reid and Dean (2000). The Neanderthal charts differ from those of modern humans especially in initiation ages and in the duration of enamel formation within equivalent divisions of crown height. Based on these new charts, we estimate ages at formation for a series of Krapina Neanderthal defects. We also compare estimated ages at defect formation in the Krapina sample with estimated ages of defect formation in a sample of modern humans from Point Hope, Alaska. The median ages at defect formation across different anterior tooth types range from 2.3–2.5 (based on a seven-day perikymata periodicity) and 2.6–2.8 years (based on an eight-day perikymata periodicity), suggesting that Neanderthals experienced physiological stress earlier in life than indicated by previous estimates that were derived from modern human standards. By contrast, median ages at defect formation in the Point Hope sample are later than those of the Krapina Neanderthals, which may result from differences in crown growth geometry between Neanderthals and modern humans, differences between the two populations in the ages at which they experienced episodes of stress, or both.