Doctoral Dissertation Research: Dental Analysis of Classic Period Population Variability in the Maya Region

这项研究将使用古人类骨骼遗骸中的牙齿测量和非测量数据来检验经典时期玛雅人的生物变异性。在体质人类学中，对生物距离和变异性的分析可以分为无模型分析和模型约束分析。在非模型方法中，低水平的生物变异性被视为高水平相关祖先和基因流动的证据。相比之下，模型约束方法考虑了遗传漂移的影响，因此提供了一个更令人满意的古代种群动态模型。在这项研究中，将同时使用无模型和有模型约束的方法。将模型约束分析应用于经典玛雅的研究的主要好处之一是，可以从考古遗址获得大量骨骼样本，这些样本具有众所周知的人口估计和良好控制的年代学；这些因素在以前的模型约束分析中很难控制。这项研究将解决玛雅考古学特有的问题，并将产生一个关于哥伦布之前中美洲牙齿形态的大型数据集，进一步加深我们对美洲古代生物变异的理解。在这项关于古代玛雅生物变异的研究中，谢勒将检验这样一个假设，即古典时期玛雅遗址种群之间的生物距离与遗址之间的地理距离相关。这一假设基于这样的假设，即玛雅城市中心之间的迁移相对较小，人口规模的增加主要是由于人口的自然增长。然而，目前的考古证据表明，这些假设是不正确的。最近对玛雅人口学的研究表明，在古典时期，许多遗址的人口规模都有波动。迁徙，包括在主要考古地区的迁徙，可能是这些时期的消长的一种解释。此外，玛雅人的历史记录描述了古典时期的许多移民事件，包括地点间的婚姻，外国领主在被征服的地点的安置，以及通过分裂王朝血统建立新的地点。然而，缺乏的是从生物学的角度理解古代玛雅人的历史。这项研究将通过提供第一个关于玛雅低地生物变异的全面研究来填补这一空白。如果这项研究确定种群不像第一个假设中假设的那样是稳定的，那么就有必要评估古代玛雅社会的哪些部分是流动的。因此，谢勒将检验第二个假设，即当基因流动发生在古典时期时，它主要发生在社会的精英水平。每个遗址的数据将根据埋葬背景和停尸房的可变性被划分为精英和非精英部分。如果精英迁徙比非精英迁徙更大，我们应该期待普通人迁徙地点之间的生物学差异比精英迁徙更大。作为检查经典时期种群稳定性的另一种方法，样本将按时间段划分，以检查每个地点随时间的遗传连续性的相对程度。为了验证这些假设，谢勒将从代表玛雅地区七个考古区的15个地点收集牙齿测量和非测量数据。统计分析将采用无模型和有模型约束两种方法。无模型统计将包括Mahalanobis D2(指标)和离散度的平均值(非指标)。模型界限分析将遵循最近对度量和非度量数据迁移的R矩阵模型进行的统计修改。这一奖项将产生更广泛的影响，为学生的专业发展做出贡献，并为他提供国际经验。

This research will examine biological variability among the Classic period Maya using dental metric and nonmetric data from ancient human skeletal remains. Analyses of biological distance and variability within physical anthropology can be classified as model-free and model-bound. In model-free approaches, low levels of biological variability are treated as evidence for high levels of related ancestry and gene flow. In contrast, model-bound approaches take into account the affects of genetic drift and thus provide a more satisfying model of ancient population dynamics. In this study, both model-free and model-bound approaches will be utilized. One of the major benefits of applying model-bound analyses to the study of the Classic Maya is the availability of large skeletal samples sizes from archaeological sites with well-known population estimates and well-controlled chronologies; factors that have been difficult to control in previous model-bound analyses. This study will address problems both specific to Maya archaeology and will produce a large data set on Pre-Columbian Central American dental morphology, furthering our understanding of ancient biological variation in the Americas. In this study of ancient Maya biological variation, Scherer will test the hypothesis that biological distance between Classic period Maya site populations is correlated with geographic distances between sites. This hypothesis rests on the assumptions that migration between Maya urban centers was relatively minor and that increases in population size were largely due to natural population growth. Current archaeological evidence, however, suggests that these assumptions are not correct. Recent studies of Maya demography have demonstrated that numerous sites exhibit fluctuations in population size during the Classic period. Migration, including movement across major archaeological regions, may be one explanation for these episodes of growth and decline. Further, the Maya historical record describes numerous migration events during the Classic period, including inter-site marriages, the placement of foreign lords at subjugated sites, and the founding of new sites by splintering dynastic lineages. What is lacking, however, is an understanding of ancient Maya population history from a biological perspective. This research will fill that void by providing the first comprehensive study of biological variation in the Maya lowlands.If this research determines that populations were not stable, as posited in the first hypothesis, it will be necessary to evaluate what segments of ancient Maya society were mobile. Thus, Scherer will test a second hypothesis that when gene flow occurred during the Classic period, it was primarily at the elite level of society. The data for each site will be partitioned into elite and non-elite segments based on burial context and mortuary variability. If elite migration was more substantial than non-elite migration, we should expect greater biological differentiation between sites for commoners than for the elite. As an additional way to examine population stability during the Classic period, the samples will be divided by time period to examine the relative degree of genetic continuity through time for each site. In order to test these hypotheses, Scherer will collect dental metric and nonmetric data from 15 sites representing seven of the archaeological zones in the Maya region. Statistical analyses will employ both model-free and model-bound approaches. Model-free statistics will include Mahalanobis D2 (metrics) and the mean measure of divergence (nonmetrics). Model-bound analyses will follow recent statistical modifications of the R matrix model of migration for metric and nonmetric data. This award will have the broader impact of contributing to the professional development of the student and providing him with an international experience.