Most organisms have finite life spans. The maximum life span of mammals, for example, is at most some years, decades, or centuries. Why not thousands of years or more? Can we explain and predict maximum life spans theoretically, based on other traits of organisms and associated ecological constraints? Existing theory provides reasons for the prevalence of ageing, but making explicit quantitative predictions of life spans is difficult. Here, I show that there are important unappreciated differences between two backbones of the theory of senescence: Peter Medawar's verbal model, and William Hamilton's subsequent mathematical model. I construct a mathematical model corresponding more closely to Medawar's verbal description, incorporating mutations of large effect and finite population size. In this model, the drift barrier provides a standard by which the limits of natural selection on age‐specific mutations can be measured. The resulting model reveals an approximate quantitative explanation for typical maximum life spans. Although maximum life span is expected to increase with population size, it does so extremely slowly, so that even the largest populations imaginable have limited ability to maintain long life spans. Extreme life spans that are observed in some organisms are explicable when indefinite growth or clonal reproduction is included in the model.

中文翻译：

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长寿和漂移障碍：弥合Medawar和Hamilton之间的鸿沟。

大多数生物的寿命有限。例如，哺乳动物的最大寿命最多为数年，数十年或几个世纪。为什么不数千年或更久？我们能否根据生物的其他特征和相关的生态约束来理论上解释和预测最大寿命？现有的理论为衰老的流行提供了原因，但是很难对寿命进行明确的定量预测。在这里，我证明了衰老理论的两个主干之间存在重要的，未认识到的重大差异：彼得·梅达瓦尔的言语模型和威廉·汉密尔顿的后续数学模型。我建立了一个更接近Medawar口头描述的数学模型，并结合了具有较大影响和有限人口规模的突变。在这个模型中 漂移障碍提供了一个标准，通过该标准可以测量针对特定年龄突变的自然选择限制。所得模型揭示了典型最大寿命的近似定量解释。尽管预计最大寿命会随着人口规模的增长而增加，但增长速度却非常缓慢，因此，即使可以想象到的最大人口，维持长寿命的能力也很有限。当模型中包含不确定的生长或克隆繁殖时，可以解释在某些生物中观察到的极端寿命。因此，即使可以想象的最大人口，维持长寿的能力也有限。当模型中包含不确定的生长或克隆繁殖时，可以解释在某些生物中观察到的极端寿命。因此，即使可以想象的最大人口，维持长寿的能力也有限。当模型中包含不确定的生长或克隆繁殖时，可以解释在某些生物中观察到的极端寿命。