Evolutionary theory posits that grandmothers can increase their inclusive fitness by investing time and resources in their grandchildren. According on the X-linked grandmother hypothesis, the asymmetric inheritance of X-chromosomes should be responsible for the biased effect of the investment by maternal and paternal grandmothers towards granddaughters and grandsons. The British Millennium Cohort Study (n=4445 children) was used to investigate the association between grandmaternal childcare and children’s injuries between the ages of 9 months and 3 years. Support was found for the X-linked grandmother hypothesis predicting that the investment of paternal grandmothers benefits more granddaughters than grandsons, the investment of paternal grandmothers benefits granddaughters more than the investment of maternal grandmothers, and the investment of maternal grandmothers is similarly associated with the injuries of granddaughters and grandsons. However, no support was found for the prediction that maternal grandmothers benefit more grandsons than paternal grandmothers. Thus, some, although not univocal, evidence for the prediction that X-chromosomal relatedness shapes the grandmaternal effect on child outcomes was found.

中文翻译：

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祖母投资和儿童早期伤害：X染色体相关性的作用

进化论认为，祖母可以通过在孙辈身上投入时间和资源来提高他们的包容性。根据X连锁祖母假说，X染色体的不对称遗传应该是造成外祖母和外祖母对孙女和孙子投资的偏向效应的原因。英国千年队列研究（n= 4445 名儿童）用于调查祖母育儿与 9 个月至 3 岁儿童伤害之间的关系。X 连锁祖母假说得到支持，即祖母的投资对孙女的好处多于孙子，祖母的投资对孙女的好处多于外祖母的投资，外祖母的投资与伤害的相关性类似的孙女和孙子。然而，没有发现外祖母比外祖母更能惠及孙子的预测。因此，发现了一些（尽管不是唯一的）证据来预测 X 染色体相关性决定了祖母对儿童结局的影响。