Human Osteology Lab, School of Anthropology and Conservation, University of Kent, Canterbury, UK.
Department of Anthropology, The Ohio State University, Columbus, Ohio, USA.
Am J Phys Anthropol. 2021 May;175(1):172-186. doi: 10.1002/ajpa.24206. Epub 2020 Dec 24.
Human tooth enamel retains evidence of growth in the form of Retzius lines. The number of daily growth increments between the regularly occurring lines defines their repeat interval, or periodicity. Retzius periodicity is often incorporated into enamel formation times, age-at-death reconstructions, or used to provide a basis from which to explore an underlying biorhythm. Biological anthropologists typically assume that RP remains constant within an individual and does not vary along the tooth-row. Here, we test that assumption.
RP was calculated from n = 223 thin sections of human permanent teeth from individuals of British and southern African origin. Forty individuals provided multiple teeth (n = 102 teeth) and a further 121 individuals each provided a single tooth.
We report first evidence that RP of permanent teeth does not always remain constant within an individual. Of those individuals that provided multiple teeth, 42% (n = 17/40) demonstrated a decrease in RP along the tooth row, with most shifting by two or more days (n = 11). Across the entire sample, mean RP of anterior teeth was significantly higher than molars. Mean premolar RP tended to be intermediate between anterior teeth and molars.
Our data do not support the assumption that RP invariably remains constant within the permanent teeth of an individual. Transferring RP from molars to incisors within an individual can result in a miscalculation of formation time and age-at-death by up to 1 year. Implications for biological anthropologists and the source of the underlying long period biorhythm are discussed.
人类牙釉质保留了生长的证据，表现为雷特氏线。定期出现的线之间的每日生长增量数定义了它们的重复间隔或周期性。雷特氏周期性通常被纳入牙釉质形成时间、死亡年龄重建或用于提供探索潜在生物节律的基础。生物人类学家通常假设 RP 在个体内部保持不变，并且不会沿牙列变化。在这里，我们检验了这一假设。
从英国和南非起源的个体的 223 个人类恒牙薄片中计算了 RP。40 名个体提供了多个牙齿（n=102 颗牙齿），另有 121 名个体各提供了一颗牙齿。
我们首次报告了 RP 并不总是在个体内部保持不变的证据。在提供多个牙齿的个体中，42%（n=17/40）沿牙列表现出 RP 的下降，其中大多数下降了两天或更多（n=11）。在整个样本中，前牙的平均 RP 明显高于磨牙。平均前磨牙的 RP 倾向于在前牙和磨牙之间处于中间位置。
我们的数据不支持 RP 在个体的恒牙中始终保持不变的假设。在个体中将 RP 从磨牙转移到切牙可能导致形成时间和死亡年龄的计算错误高达 1 年。讨论了对生物人类学家的影响以及潜在长周期生物节律的来源。
