Center for Functional Anatomy and Evolution, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Am J Phys Anthropol. 2011 Aug;145(4):615-28. doi: 10.1002/ajpa.21554. Epub 2011 Jun 23.
The extent to which the mandibular corpus exhibits developmental plasticity has important implications for interpreting variation in adult and juvenile mandibular morphology in the archaeological and paleontological record. Here, we examine ontogenetic changes in mandibular corpus breadth, rigidity, and strength in two population samples with contrasting diets: late prehistoric Tigara from Point Hope, Alaska, characterized by a very demanding masticatory regime, and proto-historic Arikara from the Sully Site in South Dakota, with a less demanding regime. A total of 52 juvenile and 11 adult Tigara, and 32 juvenile and 10 adult Arikara were included in the study. Juveniles ranged in age from 1 to 17 years, with good representation of younger (1-6-year-old) juveniles (20 Arikara, 18 Tigara). Superoinferior and buccolingual external and cortical bone breadths of mandibles were measured at the Pm(4) -M(1) and M(1) -M(2) junctions using calipers and biplanar radiographs, respectively. An asymmetrical hollow beam model was employed to reconstruct cross sections and calculate bending rigidities and strengths in the sagittal and transverse planes. Among adults, Tigara have greater transverse corpus width, bending rigidity, and strength, and ratios of transverse to sagittal dimensions than Arikara. This shape difference develops gradually during growth, with only weak trends among young juveniles, increasing to near-adult contrasts among adolescents. These results support a role for functional mechanical loading of the mandible during growth in producing adult differences in mandibular corpus morphology.
下颌骨在多大程度上表现出发育可塑性，对于解释考古学和古生物学记录中成年和幼年下颌形态的变化具有重要意义。在这里，我们研究了两个饮食结构截然不同的人群样本中下颌骨体宽度、刚性和强度的发育变化：来自阿拉斯加希望角的晚期史前 Tigara，具有非常高的咀嚼需求，以及来自南达科他州 Sully 遗址的原始历史 Arikara，其咀嚼需求较低。共有 52 名青少年和 11 名成年 Tigara，32 名青少年和 10 名成年 Arikara 被纳入研究。青少年年龄从 1 岁到 17 岁不等，有很好的代表性（20 名 Arikara，18 名 Tigara）。使用卡尺和双平面射线照相术分别测量了下颌 Pm(4) -M(1) 和 M(1) -M(2) 交界处的上下和颊舌外部及皮质骨宽度。采用非对称空心梁模型重建横截面，并计算矢状面和横断面上的弯曲刚性和强度。在成年人中，Tigara 的横向体宽、弯曲刚性和强度以及横向与矢状尺寸的比值均大于 Arikara。这种形状差异在生长过程中逐渐发展，在年轻的青少年中只有微弱的趋势，在青少年中增加到接近成年的差异。这些结果支持在生长过程中下颌骨的功能性机械负荷在产生成年下颌骨体形态差异方面的作用。
