Smith Timothy D, Muchlinski Magdalena N, Bucher Wade R, Vinyard Christopher J, Bonar Christopher J, Evans Sian, Williams Lawrence E, DeLeon Valerie B
School of Physical Therapy, Slippery Rock University, Slippery Rock, Pennsylvania 16057.
Department of Anthropology, University of Pittsburgh, Pittsburgh, Pennsylvania.
Am J Phys Anthropol. 2017 Nov;164(3):623-634. doi: 10.1002/ajpa.23302. Epub 2017 Aug 19.
Dental eruption schedules have been closely linked to life history variables. Here we examine a sample of 50 perinatal primates (28 species) to determine whether life history traits correlate with relative tooth size at birth.
Newborn primates were studied using serial histological sectioning. Volumes of deciduous premolars (dp -dp ), replacement teeth (if any), and permanent molars (M ) of the upper jaw were measured and residuals from cranial length were calculated with least squares regressions to obtain relative dental volumes (RDVs).
Relative dental volumes of deciduous or permanent teeth have an unclear relationship with relative neonatal mass in all primates. Relative palatal length (RPL), used as a proxy for midfacial size, is significantly, positively correlated with larger deciduous and permanent postcanine teeth. However, when strepsirrhines alone are examined, larger RPL is correlated with smaller RDV of permanent teeth. In the full sample, RDVs of deciduous premolars are significantly negatively correlated with relative gestation length (RGL), but have no clear relationship with relative weaning age. RDVs of molars lack a clear relationship with RGL; later weaning is associated with larger molar RDV, although correlations are not significant. When strepsirrhines alone are analyzed, clearer trends are present: longer gestations or later weaning are associated with smaller deciduous and larger permanent postcanine teeth (only gestational length correlations are significant).
Our results indicate a broad trend that primates with the shortest RGLs precociously develop deciduous teeth; in strepsirrhines, the opposite trend is seen for permanent molars. Anthropoids delay growth of permanent teeth, while strepsirrhines with short RGLs are growing replacement teeth concurrently. A comparison of neonatal volumes with existing information on extent of cusp mineralization indicates that growth of tooth germs and cusp mineralization may be selected for independently.
牙齿萌出时间表与生活史变量密切相关。在此，我们研究了50只围产期灵长类动物（28个物种）的样本，以确定生活史特征是否与出生时的相对牙齿大小相关。
使用连续组织切片法对新生灵长类动物进行研究。测量上颌乳前磨牙（dp -dp ）、替换牙（如有）和恒磨牙（M ）的体积，并通过最小二乘法回归计算颅长的残差，以获得相对牙齿体积（RDV）。
在所有灵长类动物中，乳牙或恒牙的相对牙齿体积与相对新生儿体重的关系不明确。用作中面部大小指标的相对腭长（RPL）与较大的乳恒牙后犬齿显著正相关。然而，单独检查狐猴时，较大的RPL与恒牙的较小RDV相关。在整个样本中，乳前磨牙的RDV与相对妊娠期长度（RGL）显著负相关，但与相对断奶年龄没有明确关系。磨牙的RDV与RGL缺乏明确关系；断奶较晚与较大的磨牙RDV相关，尽管相关性不显著。单独分析狐猴时，有更明显的趋势：妊娠期较长或断奶较晚与较小的乳牙和较大的恒牙后犬齿相关（仅妊娠期长度的相关性显著）。
我们的结果表明一个广泛的趋势，即RGL最短的灵长类动物早熟乳牙；在狐猴中，恒牙则呈现相反的趋势。类人猿延缓恒牙生长，而RGL短的狐猴同时生长替换牙。将新生儿体积与现有关于牙尖矿化程度的信息进行比较表明，牙胚生长和牙尖矿化可能是独立选择的。
