Baxter Alexander, Wood Elizabeth K, Jarman Parker, Cameron Ashley N, Capitanio John P, Higley J Dee
Department of Psychology, Brigham Young University, Provo, UT, United States.
California National Primate Research Center (CNPRC), Davis, CA, United States.
Front Behav Neurosci. 2018 Sep 21;12:213. doi: 10.3389/fnbeh.2018.00213. eCollection 2018.
Prenatal androgen exposure (PAE) plays a pivotal role in masculinizing the developing body and brain, and extreme exposure may contribute to autism, anxiety disorder and schizophrenia. One commonly used biomarker for PAE is the pointer-to-ring-finger digit length (2D:4D) ratio. Although this biomarker is widely used in human studies, relatively few studies have investigated 2D:4D ratio in nonhuman primates, particularly rhesus macaques (), one of the most commonly used animals in biomedical research. Thus far, data suggest that sexual dimorphism in 2D:4D ratio may be in the opposite direction in some monkey species, when compared to the pattern exhibited by humans and great apes. Using a large sample size, we investigated whether rhesus monkeys' 2D:4D ratio shows the same sex-differentiated pattern present in other Old World monkey species. We also investigated whether individual differences in 2D:4D ratio are associated with the social dominance rank of subjects' mothers during pregnancy, and the social dominance rank the subjects attained as adults. Subjects were 335 rhesus monkeys between 3 years and 24 years of age ( = 6.6). Maternal dominance rank during pregnancy and subjects' adult dominance rank were categorized into tertiles (high, middle and low). Results showed that, across both hands, male rhesus monkeys exhibited higher 2D:4D ratio than females, a pattern consistent with other monkey species and a reversal from the pattern typically observed in humans and apes. This sex difference was modulated by maternal dominance rank, with female offspring of high-ranking and middle-ranking mothers exhibiting masculinized 2D:4D ratio, indicating that maternal dominance rank during pregnancy may influence levels of PAE. There was no association between subjects' 2D:4D ratio and the social dominance rank they attained as adults. These findings show a consistent sex difference in Old World monkeys' 2D:4D ratio that diverges from the pattern observed in apes and humans, and suggest maternal social dominance rank modulates PAE in rhesus monkeys.
产前雄激素暴露（PAE）在使发育中的身体和大脑男性化过程中起着关键作用，而极端暴露可能导致自闭症、焦虑症和精神分裂症。一种常用的PAE生物标志物是食指与无名指长度（2D:4D）比值。尽管这种生物标志物在人类研究中被广泛使用，但相对较少的研究调查了非人类灵长类动物，特别是恒河猴（生物医学研究中最常用的动物之一）的2D:4D比值。到目前为止，数据表明，与人类和大猩猩所呈现的模式相比，某些猴子物种中2D:4D比值的性别二态性可能方向相反。我们使用大样本量，研究了恒河猴的2D:4D比值是否呈现出与其他旧世界猴物种相同的性别差异模式。我们还研究了2D:4D比值的个体差异是否与受试者母亲孕期的社会优势等级以及受试者成年后获得的社会优势等级相关。受试者为335只3岁至24岁的恒河猴（平均年龄 = 6.6岁）。孕期母亲的优势等级和受试者成年后的优势等级被分为三个等级（高、中、低）。结果表明，在两只手上，雄性恒河猴的2D:4D比值均高于雌性，这一模式与其他猴子物种一致，与人类和猿类通常观察到的模式相反。这种性别差异受到母亲优势等级的调节，高等级和中等等级母亲的雌性后代表现出男性化的2D:4D比值，表明孕期母亲的优势等级可能会影响PAE水平。受试者的2D:4D比值与他们成年后获得的社会优势等级之间没有关联。这些发现表明，旧世界猴的2D:4D比值存在一致的性别差异，与猿类和人类观察到的模式不同，并表明母亲的社会优势等级调节了恒河猴的PAE。
