Evolutionary biologists often predict the outcome of natural selection on an allele by measuring its effects on lifetime survival and reproduction of individual carriers. However, alleles affecting traits like sex, evolvability, and cooperation can cause fitness effects that depend heavily on differences in the environmental, social, and genetic context of individuals carrying the allele. This variability makes it difficult to summarize the evolutionary fate of an allele based solely on its effects on any one individual. Attempts to average over this variability can sometimes salvage the concept of fitness. In other cases evolutionary outcomes can only be predicted by considering the entire genealogy of an allele, thus limiting the utility of individual fitness altogether. We describe a number of intriguing new evolutionary phenomena that have emerged in studies that explicitly model long-term lineage dynamics and discuss implications for the evolution of infectious diseases.

中文翻译：

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适应性效应的可变性可能会妨碍选择适者

进化生物学家经常通过测量自然选择对个体携带者终生生存和繁殖的影响来预测自然选择对等位基因的结果。然而，影响性别、进化性和合作等特征的等位基因会导致健康效应，这在很大程度上取决于携带等位基因的个体的环境、社会和遗传背景的差异。这种可变性使得很难仅根据等位基因对任何个体的影响来总结等位基因的进化命运。尝试对这种可变性进行平均有时可以挽救适应度的概念。在其他情况下，进化结果只能通过考虑等位基因的整个谱系来预测，从而完全限制了个体适应性的效用。