- by Astrid Slizewski
“The Cova Negra infant radius was analysed for its biomechanical properties and compared to one Neanderthal and one Palaeolithic modern human infant radius. Results indicate a different pattern of cortical thickness distribution and biomechanical properties along the shaft in Neanderthal and modern human children.
It has been suggested by several authors that a thick cortical bone might be a systemic feature of development and growth in Neanderthals (Ruff et al. 1994; Churchill 1998). This theory has been based on femoral morphology of only two immature Neanderthal specimens (Teshik-Tash 1 and La Ferrassie 6) and requires further investigations in order to be confirmed or declined. If thick cortices are indeed a systemic feature of Neanderthals, the cortical bone of young Neanderthals should be clearly thicker than that of Palaeolithic modern children and recent modern children and this difference should be observable in all long bones. This underlying assumption provides a basis for testing the systemic feature hypothesis. The question whether thick cortices are a systemic feature of Neanderthals is an essential one for understanding Neanderthal and modern human skeletal development. If very young Neanderthal children are morphologically robust, this leaves us with only two possibilities: First, a difference in cortical thickness could be genetically determined. This becomes more probable if a significant difference between modern human and Neanderthal cortical thickness is observed in infant specimens as there was less time for the infant bone to adapt to mechanical loadings than for adult bone. Still, only for fetal and neonatal specimens a habitual influence can be ruled out completely if one does not imply that movement rates in utero are different between Neanderthals and modern humans (see e.g., Forst & Schoenau 2000; Gomez et al. 2007 and Sharir et al. 2011 for theories and studies on in utero skeletal adaptation). A preliminary study assessing the cross-sectional shape of the humerus and tibia of Amud 7, a 9.5 month old Neanderthal infant, has provided cross-sectional shape values similar to those of modern human samples (Odwak 2001). This single observation supports Trinkaus et al.’s (1994) argument that diaphyseal morphology is rather an expression of activity-related tasks than of genetic influences. Further data is required in order to underline or invalidate the finding of Odwak (2001). However, given the scarcity of well-preserved neonatal or foetal Neanderthal limb bones in the fossil record, identifying possible genetic differences that might influence bone morphology based only on skeletal remains will be a challenging task. Secondly, there could have been differences in behaviour that caused diverging skeletal adaptations in Neanderthal and modern human children. Possible behavioural factors that might cause differences in bone morphology of preadolescents include the degree of involvement in mechanically challenging subsistence activities (Grupe & Bach 1993) and nutrition including period and frequency of lactation (Monteiro et al. 2010). Thompson & Nelson (2005, 2011) hypothesised that the juvenile Neanderthal Moustier 1 (age 11 years; Thompson & Nelson 2011), already participated in physically demanding adult activities. However, if thicker cortices are not a systemic feature of Neanderthal children, thicker cortical bone in adult Neanderthals will probably be due to high mechanical loadings rather than genetic factors” (read more/open access).
(Open access source: Andreas Pastoors & Bärbel Auffermann (eds.). Pleistocene Foragers: Their Culture and Environment. Festschrift in Honour of Gerd-Christian Weniger for his Sixtieth Birthday. Wissenschaftliche Schriften des Neanderthal Museums 6, Mettmann, 2013 via Academia.edu; bottom images: Schaefer M, Black S and Scheuer L. 2009. Juvenile Osteology: A Laboratory and Field Manual. Elsevier)
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