3D enamel profilometry reveals faster growth but similar stress severity in Neanderthal versus Homo sapiens teeth

Abstract

Early life stress disrupts growth and creates horizontal grooves on the tooth surface in humans and other mammals, yet there is no consensus for their quantitative analysis. Linear defects are considered to be nonspecific stress indicators, but evidence suggests that intermittent, severe stressors create deeper defects than chronic, low-level stressors. However, species-specific growth patterns also influence defect morphology, with faster-growing teeth having shallower defects at the population level. Here we describe a method to measure the depth of linear enamel defects and normal growth increments (i.e., perikymata) from high-resolution 3D topographies using confocal profilometry and apply it to a diverse sample of Homo neanderthalensis and H. sapiens anterior teeth. Debate surrounds whether Neanderthals exhibited modern human-like growth patterns in their teeth and other systems, with some researchers suggesting that they experienced more severe childhood stress. Our results suggest that Neanderthals have shallower features than H. sapiens from the Upper Paleolithic, Neolithic, and medieval eras, mirroring the faster growth rates in Neanderthal anterior teeth. However, when defect depth is scaled by perikymata depth to assess their severity, Neolithic humans have less severe defects, while Neanderthals and the other H. sapiens groups show evidence of more severe early life growth disruptions.

Paleoecology of the Rhinocerotidae (Mammalia, Perissodactyla) from Béon 1, Montréal-du-Gers (late early Miocene, SW France): Insights from dental microwear texture analysis, mesowear, and enamel hypoplasia

“…We found that deciduous teeth were less affected than permanent teeth. This has been reported in several other studies focusing on various mammals (Dobney and Ervynck, 1998;Lukacs, 1999;Bacon et al, 2018;Towle and Irish, 2019;McGrath et al, 2021), and several factors might explain this difference. First, in rhinocerotids, deciduous teeth develop partially (d1/D1 and d4/ D4) or totally (d2/D2 and d3/D3) in utero, which provides a relatively stable environment (Hitchins, 1978;Hillman-Smith et al, 1986;Böhmer et al, 2016).…”

Growth of Neanderthal infants from Krapina (120–130 ka), Croatia

“…A short postnatal enamel formation period has been reported for a deciduous incisor of the Fumane 2 upper Palaeolithic modern human infant (39-42 ka) [29], which differs from longer enamel growth periods reported for extant humans [37]. Relatively rapid formation rates have also been reported for Neanderthal permanent anterior teeth [21,47].…”

Childhood stress and developmental instability: Comparing microscopic enamel defects and cranial fluctuating asymmetry in a colonial Mexican sample

“…This is because defect margins are not always well-defined due to the curvature of the tooth and differences in perikymata widths within a defect (Hillson & Bond, 1997). Research using enamel depth profiles and/or micro-CT imaging may remedy the issue of subjective defect and duration identification (e.g., Cares Henriquez & Oxenham, 2020;McGrath et al, 2021;Xing et al, 2016). However, such methodology is associated with its own set of limitations because it requires specialized equipment that cannot usually be applied to larger bioarchaeological samples required for studies of FA, caused by restrictions from data collection and travel.…”