Abstract Demographic data from 848 Gabbra households are used to examine the relationships between herd size and reproductive success in relation to sex, in a traditional, pastoralist population. The number of camels in the household herd has a significant positive effect on the reproductive success of both men and women, although the effect of wealth is greater for men, as predicted from evolutionary theory. The greater the number of elder brothers a man has, the lower his reproductive success, as a result of a smaller initial herd and a later age at marriage. This is not true for women –number of elder sisters does not have a measurable effect on a woman’s fertility, although it does have a small, negative effect on the size of her dowry. These results are interpreted as competition between same-sex siblings for parental investment, in the form of their father’s herd, which is more intense between sons than daughters as parental investments are greatest in males.

中文翻译：

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加布拉牧民的有偏见的父母投资和繁殖成功

摘要 来自 848 个 Gabbra 家庭的人口统计数据用于检查传统牧民人口中畜群规模与与性别相关的繁殖成功之间的关系。正如进化论预测的那样，尽管财富对男性的影响更大，但家庭畜群中的骆驼数量对男性和女性的繁殖成功率都有显着的积极影响。一个男人的哥哥越多，他的繁殖成功率就越低，这是由于最初的数量较少，结婚年龄较晚。对于女性而言，情况并非如此——姐姐的数量对女性的生育能力没有可衡量的影响，尽管它确实对她的嫁妆规模产生了微小的负面影响。这些结果被解释为同性兄弟姐妹之间对父母投资的竞争，