Lynch Robert F, Lynch Emily C
Department of Anthropology, University of Missouri , Columbia , MO , United States.
PeerJ. 2017 Jan 19;5:e2904. doi: 10.7717/peerj.2904. eCollection 2017.
Demonstrating the impact that parents have on the fitness of their children is a crucial step towards understanding how parental investment has affected human evolution. Parents not only transfer genes to their children, they also influence their environments. By analyzing reproductive patterns within and between different categories of close relatives, this study provides insight into the genetic and environmental effects that parents have on the fitness of their offspring.
We use data spanning over two centuries from an exceptionally accurate Icelandic genealogy, Íslendingabók, to analyze the relationship between the fertility rates of close relatives. Also, using genetic data, we determine narrow sense heritability estimates () to further explore the genetic impact on lifetime reproductive success. Finally, we construct four simulations to model the expected contribution of genes and resources on reproductive success.
The relationship between the reproduction of all full sibling pairs was significant and positive across all birth decades ( = 0.19) while the reproductive relationship between parents and offspring was often negative across many decades and undetectable overall ( = 0.00) (Fig. 1 and Table 1). Meanwhile, genetic data among 8,456 pairs of full siblings revealed a narrow sense heritability estimate () of 0.00 for lifetime reproductive success. A resources model (following the rule that resources are transmitted from parents to children, distributed equally among siblings, and are the only factor affecting reproductive success) revealed a similar trend: a negative relationship between parent and offspring reproduction ( = - 0.35) but a positive relationship among full siblings ( = 0.28). The relationship between parent and offspring lifetime reproductive success (LRS) and full sibling LRS was strongly and positively correlated across time ( = 0.799, < 0.001). Similarly, the LRS among full siblings was positively correlated with both the LRS among half siblings ( = 0.532, = 0.011) and the relationship between the LRS of aunts and uncles with their nieces and nephews ( = 0.438, = 0.042).
We show that an individual's lifetime reproductive success is best predicted by the reproduction of their full and half siblings, but not their parents, grandparents or aunts and uncles. Because all siblings share at least one parent, we believe parental investment has had an important impact on fitness. Overall, these results indicate that direct parental investment, but not genes, is likely to have had an important and persistent impact on lifetime reproductive success across more than two centuries of Icelandic history.
证明父母对子女健康状况的影响是理解父母投资如何影响人类进化的关键一步。父母不仅将基因传递给子女，还会影响他们的环境。通过分析不同类别近亲内部和之间的生殖模式，本研究深入了解了父母对后代健康状况的基因和环境影响。
我们使用了跨越两个多世纪、来自极其精确的冰岛族谱《冰岛人之书》的数据，来分析近亲生育率之间的关系。此外，利用基因数据，我们确定狭义遗传力估计值（），以进一步探索对终身生殖成功的基因影响。最后，我们构建了四个模拟模型，以模拟基因和资源对生殖成功的预期贡献。
在所有出生十年中，所有全同胞对的生殖之间的关系均显著且呈正相关（ = 0.19），而父母与子女之间的生殖关系在许多十年中往往呈负相关，总体上无法检测到（ = 0.00）（图1和表1）。同时，8456对全同胞的基因数据显示，终身生殖成功的狭义遗传力估计值（）为0.00。一个资源模型（遵循资源从父母传递给子女、在兄弟姐妹之间平均分配且是影响生殖成功的唯一因素的规则）显示了类似的趋势：父母与子女生殖之间呈负相关（ = - 0.35），但全同胞之间呈正相关（ = 0.28）。父母与子女终身生殖成功（LRS）以及全同胞LRS之间的关系在时间上呈强正相关（ = 0.799， < 0.001）。同样，全同胞之间的LRS与半同胞之间的LRS（ = 0.532， = 0.011）以及叔伯姑姨与侄甥之间的LRS关系（ = 0.438， = 0.042）均呈正相关。
我们表明，一个人的终身生殖成功最好由其全同胞和半同胞的生殖情况来预测，而不是由其父母、祖父母或叔伯姑姨来预测。因为所有兄弟姐妹至少共享一位父母，我们认为父母投资对健康状况有重要影响。总体而言，这些结果表明，在冰岛两个多世纪的历史中，直接的父母投资而非基因，可能对终身生殖成功产生了重要且持久的影响。
