UMR 7194 HNHP, University of Perpignan Via Domitia, EPCC-CERP de Tautavel, Avenue Léon Jean Grégory 66720 Tautavel, France.
UMR 5199 PACEA, University of Bordeaux, CNRS, MCC; LabEx Sciences Archéologiques de Bordeaux, N°ANR-10-LABX-52, Bâtiment B8, Allée Geoffroy Saint-Hilaire, CS50023, F-33615 Pessac, France; Department of Orthodontics, University of Lille, F-59000, Lille, France.
J Hum Evol. 2021 May;154:102968. doi: 10.1016/j.jhevol.2021.102968. Epub 2021 Mar 26.
Trabecular bone ontogeny is well known in modern humans and unknown in Neandertals. Yet the bone developmental pattern is useful for interpreting fossils from evolutionary and functional perspectives. Interestingly, microstructure in early ontogeny is supposedly not influenced by high and specific mechanical loading related to the lifestyle of a human group and consequently does not directly depend on the activities of hunter-gatherers. Here, we specifically explored the early growth trajectories of the trabecular bone structure of the humerus and emphasized in particular how bone fraction (bone volume/total volume [BV/TV]) was built up in Neandertals, given the specific modern human bone loss after birth and the use of BV/TV in functional studies. Six Neandertals and 26 recent modern humans ranging from perinates to adolescents were included in this study. Six trabecular parameters were measured within a cubic region of interest extracted from the proximal metaphysis of the humerus. We found that the microstructural changes in Neandertals during early ontogeny (<1 year) fit with modern human growth trajectories for each parameter. The specific bone loss occurring immediately after birth in modern humans also occurred in Neandertals (but not in chimpanzees). However, the early childhood fossil Ferrassie 6 presented unexpectedly high BV/TV, whereas the high BV/TV in the Crouzade I adolescent was predictable. These results suggest that Neandertals and modern humans shared predetermined early growth trajectories and developmental mechanisms. We assume that the close relationship between skeletal characteristics in early ontogeny and adults in modern humans also existed in Neandertals. However, it was difficult to ensure that the high BV/TV in Neandertal early childhood, represented by only one individual, was at the origin of the high BV/TV observed in adults. Consequently, our study does not challenge the mechanical hypothesis that explains the trabecular gracilization of the humerus during the Holocene.
小梁骨发生在现代人中是众所周知的，而在尼安德特人中则是未知的。然而，从进化和功能的角度来看，骨骼发育模式对于解释化石是有用的。有趣的是，早期发生的微观结构据说不受与人类群体生活方式相关的高特异性机械负荷的影响，因此并不直接取决于狩猎采集者的活动。在这里，我们特别探讨了肱骨小梁骨结构的早期生长轨迹，并特别强调了在特定的现代人类出生后骨丢失和在功能研究中使用骨体积/总体积 (BV/TV) 的情况下，尼安德特人是如何建立骨量的。本研究纳入了 6 名尼安德特人和 26 名从围产期到青少年的现代人类。在肱骨近端干骺端提取的立方感兴趣区内测量了 6 个小梁参数。我们发现，在早期发生（<1 岁）期间，尼安德特人的微观结构变化与每个参数的现代人类生长轨迹相吻合。现代人类出生后立即发生的特定骨丢失也发生在尼安德特人（但不在黑猩猩中）。然而，Ferrassie 6 号幼年化石出人意料地具有较高的 BV/TV，而 Crouzade I 号青少年的高 BV/TV 是可以预测的。这些结果表明，尼安德特人和现代人类共享预定的早期生长轨迹和发育机制。我们假设，在现代人类中，早期发生和成年骨骼特征之间的密切关系也存在于尼安德特人中。然而，很难确定仅代表一个个体的尼安德特人幼年时期的高 BV/TV 是否是成年时观察到的高 BV/TV 的起源。因此，我们的研究并没有挑战解释全新世肱骨小梁骨变细的机械假说。
