Examining plastic adaptive responses in the generation of human skeletal variation

骨骼形态的进化模型通常采用“形式跟随功能”的解释，重点放在成人形态的选择性背景上。但是，成人的骨骼形态是生长和发育过程的产物，这些过程本身受到选择和环境的影响。由于生物的可塑性，人类骨骼的变化在一定程度上反映了环境(气候、地形)、生态(资源可获得性、疾病负荷)和生活方式(饮食、活动、技术)背景的差异。具有挑战性的环境，营养或饮食限制，高活动预算，或高寄生虫或传染病负荷，导致骨骼生长受限，通常在骨骼和牙齿组织中留下签名，保存这些发育应激源的证据。习惯性活动通过体重和肌肉活动来加载骨骼，并改变四肢骨干中的骨组织分布。因此，骨骼形态可以提供对塑造我们物种的进化过程的洞察，以及影响种群和个人的因素。但考虑到骨骼组织的可塑性，这些过程可能并不是这些过程影响发育过程中骨骼形态的唯一方式。骨骼的关节区域被认为在发育过程中受到遗传因素的严格控制，对环境的反应较小，这表明它们的形状应该更稳定。然而，脚踝的方向与底物的使用有关，椎管也随着应力的变化而变化。这些区域存在可塑性。本研究将使用3D几何形态计量学方法，对照传统的骨骼发育应激和习惯性活动指标，研究考古提取的人类骨骼标本中四肢和椎骨的大小和形状特征，以阐明个体发育过程中的应激和活动是否以及如何影响形态。人类学家认为，灭绝的原始人的形态在很大程度上反映了它们作为正常生长的产物的进化史，而不是对环境压力的可塑性反应。但是，为了破译化石记录中形态变异的含义，我们必须了解可塑性适应性反应是如何产生骨骼形态的。这对生物考古学家也很重要，他们使用生长过程的结果作为随着时间推移人口健康的指标，以应对人口和生态变化。我的研究代表了一种新的方法来检验环境和活动对人类骨骼变异的影响。了解物种形态变异发生过程中的可塑性和约束(进化、功能、发育)之间的相互作用，有助于确定影响适应的因素(环境、生态、生活方式)，这对进化人类学家、古人类学家和进化解剖学家特别重要。

Evolutionary models for skeletal morphology often apply "form follows function" explanations, focusing on the selective context of adult morphology. But, adult skeletal form is the product of the processes of growth and development, which are themselves subject to selection, and to environmental influences. Due to biological plasticity, human skeletal variation reflects, in part, differences in environmental (climate, terrain), ecological (resource availability, disease load), and lifestyle (diet, activity, technology) contexts. Challenging environments, with nutritional or dietary limitation, high activity budgets, or high parasitic or infectious disease loads lead to restricted skeletal growth, often leaving signatures in bone and dental tissues preserving evidence of these developmental stressors. Habitual activities load bones through body weight and muscle action and alter bone tissue distribution in the shafts of limb bones. As such, skeletal morphology can offer insights on evolutionary processes shaping our species, and factors affecting populations and individuals. But given the plasticity of skeletal tissue, these may not be the only ways in which these processes influence skeletal morphology during development. Joint regions of bones are thought to be tighty controlled during development by genetic factors and less responsive to the environment, suggesting their form should be more stable. Yet, ankle orientation varies in relation to substrate use, and the vertebral canal varies with stress. Plasticity exists in these regions. This research will use 3D geometric morphometric approaches to examine the size and shape characteristics of bones of the limbs and vertebrae in archaeologically derived human skeletal samples in relation to traditional skeletal indicators of developmental stress and habitual activity, to elucidate whether and how stress and activity during ontogeny can influence morphology. Anthropologists assume the morphology of extinct hominins largely reflects their evolutionary history as a product of normal growth, rather than plastic responses to environmental stressors. But in order to decipher the meaning of morphological variation in the fossil record we must understanding how plastic adaptive responses generate skeletal morphology. This is also important for bioarchaeologists, who employ outcomes of growth processes as indicators of population health through time in response to demographic and ecological changes. My research represents a novel approach to examining the influence of environment and activity in producing skeletal variation in humans. Understanding the interplay between plasticity and constraint (evolutionary, functional, developmental) in the generation of morphological variation in a species aids in identifying factors (environmental, ecological, lifestyle) that influence adaptation, which are of particular importance to evolutionary anthropologists, paleoanthropologists, and evolutionary anatomists.