Throughout the world, there is a male-bias in the sex ratio at birth (SRB). It is not known whether this phenomenon has a genetic basis, though there is tentative evidence from genealogical and genomic studies that it may have. It has been proposed that the higher rate of male childhood mortality in humans is linked to the male-bias in SRB through parental investment, but this may only apply to facultative not genetic sex ratio adjustment. In previous population genetic models, elevated mortality in one sex (prior to breeding) has been shown not to affect the SRB, but these models did not consider the role of replacement births (i.e. births that only occur because a sibling died prematurely). In a set of population genetic modelling simulations, in which sex ratio is controlled by an autosomal gene expressed in the male line, this study shows that when there is replacement of dead offspring, this leads to a sustained bias in the SRB in the direction of the sex suffering the highest mortality. In the example of higher male mortality, this occurs, because replacement offspring are disproportionately drawn from fathers who were genetically predisposed to have initially had sons (because sons were more likely to die prematurely), and more likely to pass on male-biasing alleles to replacement offspring. To test the empirical basis for replacement births, an analysis of birth data from the Demographic and Health Survey program was conducted, which shows that parents do indeed tend to replace children who die prematurely.

中文翻译：

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出生性别比的全球男性偏见是由替代后代的性别比基因型维持的

在世界各地，出生性别比 (SRB) 存在男性偏见。目前尚不清楚这种现象是否具有遗传基础，尽管有来自家谱和基因组研究的初步证据表明它可能存在。有人提出，人类较高的男性儿童死亡率与通过父母投资的 SRB 中的男性偏见有关，但这可能仅适用于兼性而非遗传性别比例调整。在以前的群体遗传模型中，一种性别的死亡率升高（繁殖前）已被证明不会影响 SRB，但这些模型没有考虑替代生育的作用（即仅因兄弟姐妹过早死亡而发生的生育）。在一组群体遗传建模模拟中，其中性别比例由男性系中表达的常染色体基因控制，这项研究表明，当替换死亡的后代时，这会导致 SRB 持续偏向死亡率最高的性别。在男性死亡率较高的例子中，会发生这种情况，因为替代后代不成比例地来自具有最初有儿子的遗传倾向的父亲（因为儿子更有可能过早死亡），并且更有可能将偏向男性的等位基因传递给替换后代。为了检验替代生育的实证基础，对人口与健康调查计划的出生数据进行了分析，结果表明父母确实倾向于替代过早死亡的孩子。在男性死亡率较高的例子中，会发生这种情况，因为替代后代不成比例地来自具有最初有儿子的遗传倾向的父亲（因为儿子更有可能过早死亡），并且更有可能将偏向男性的等位基因传递给替换后代。为了检验替代生育的实证基础，对人口与健康调查计划的出生数据进行了分析，结果表明父母确实倾向于替代过早死亡的孩子。在男性死亡率较高的例子中，会发生这种情况，因为替代后代不成比例地来自具有最初有儿子的遗传倾向的父亲（因为儿子更有可能过早死亡），并且更有可能将偏向男性的等位基因传递给替换后代。为了检验替代生育的实证基础，对人口与健康调查计划的出生数据进行了分析，结果表明父母确实倾向于替代过早死亡的孩子。