Sciulli P W, Mahaney M C
Department of Anthropology, Ohio State University, Columbus 43210.
Hum Biol. 1991 Aug;63(4):499-511.
Many anthropologic investigations involve measurement and analysis of polygenic skeletal and dental traits in prehistoric populations from which genetic details cannot be inferred. However, population genetics concepts can be applied productively to analyses of phenotypic variation in prehistoric human populations. One potentially useful approach, derived from basic quantitative genetics (Lande 1976, p. 314), models the effects of natural selection and random genetic drift on the evolution of the average phenotype in a population. We apply this model to the problem of dental size reduction in three prehistoric Amerindian populations from Ohio. Conversion of mean log-transformed buccolingual diameters for six permanent teeth (maxillary and mandibular I1, M1, and M2) to phenotypic standard deviation units reveals significant size reduction in the maxillary teeth only. By assuming 40 generations (t) between the 2 populations and a narrow heritability (h2) range of 0.30-0.70, the estimated minimum selective mortality required to produce the reductions is 1.8 deaths per 100 persons per generation. Given the same t and h2 values, the effective population size (Ne) needed to reject the neutral hypothesis (i.e., random genetic drift) with 95% confidence is approximately 150. Because paleodemographic and ethnographic studies suggest minimum effective sizes of this magnitude for these populations, we tentatively reject random genetic drift and conclude that selective mortality is most probably responsible for the maxillary tooth size reduction observed.
许多人类学研究涉及对史前人群中多基因骨骼和牙齿特征的测量与分析，而这些人群的基因细节无法推断。然而，群体遗传学概念可以有效地应用于对史前人类群体表型变异的分析。一种源自基础数量遗传学（兰德，1976年，第314页）的潜在有用方法，对自然选择和随机遗传漂变对群体平均表型进化的影响进行建模。我们将此模型应用于来自俄亥俄州的三个史前美洲印第安人群体的牙齿尺寸减小问题。将六颗恒牙（上颌和下颌的I1、M1和M2）的平均对数转换颊舌径转换为表型标准差单位后发现，只有上颌牙齿尺寸显著减小。假设两个群体之间相隔40代（t），狭义遗传力（h2）范围为0.30 - 0.70，产生这种减小所需的估计最低选择性死亡率为每代每100人中有1.8人死亡。在相同的t和h2值下，要以95%的置信度拒绝中性假设（即随机遗传漂变）所需的有效群体大小（Ne）约为150。由于古人口统计学和人种学研究表明这些群体的最低有效大小为这个数量级，我们初步拒绝随机遗传漂变，并得出结论，选择性死亡率很可能是观察到上颌牙齿尺寸减小的原因。
