Underwood J H
Department of Anthropology, University of Arizona, Tucson 85721.
Soc Biol. 1993 Fall-Winter;40(3-4):200-6. doi: 10.1080/19485565.1993.9988846.
Secondary sex ratio (SSR) values in excess of 109 male for every 100 female livebirths have been reported from several Micronesian populations. Analyses of linked family records dating from before 1942 for the native people of Guam reveal a highly masculinized SSR even at high birth orders and parental ages of married fertile couples. These findings contrast with reported declines in SSR with parity and parental age among historical and modern populations in Europe and North America where such declines often have been ascribed to the effects of decreasing mean coital frequencies associated with marital duration and spousal age. This study challenges implicit assumptions about the supposed universality of Euroamerican patterns of marital sexual behavior and supports the coital frequency hypothesis of SSR determination.
据报道，密克罗尼西亚的几个种群的出生性别比（SSR）超过每100例女性活产中有109例男性。对关岛原住民1942年以前的相关家庭记录进行分析发现，即使在高出生顺序以及已婚育龄夫妇的父母年龄较大的情况下，SSR也高度男性化。这些发现与欧洲和北美历史及现代人群中报道的SSR随胎次和父母年龄下降形成对比，在欧美，这种下降通常归因于与婚姻持续时间和配偶年龄相关的平均性交频率降低的影响。本研究挑战了关于欧美婚姻性行为模式具有普遍性的隐含假设，并支持了SSR决定的性交频率假说。
