Deriving node calibrations from fossils remains by far the most common method for attaching an absolute timescale to a molecular tree. But this 'node dating' approach has a credibility problem: different studies using the same molecular data and even the same sets of fossils regularly arrive at drastically different age estimates. A major reason for these differences is well known: even well‐dated and firmly placed fossils can only provide a minimum age for a particular node. The time lag between that node and the fossil (or in other words: between the origin of a clade and its first appearance in the fossil record) is on the other hand notoriously difficult to quantify. Using recent studies on the age of the insect tree of life as an example, I discuss different rationales for choosing calibration priors based on fossils and argue that none of them is entirely convincing. I thus suggest shifting the objective of node dating analyses back to what can be achieved in a scientifically justifiable way: a dated tree that reflects the minimum ages of its constituent taxa. While this interpretation of time trees was followed widely in the early years of molecular dating, its conceptual advantages seem to have been suppressed over the promises of methods that allow integrating more complex node‐age constraints, even when those are difficult to justify. I argue that ‘minimum age trees’ should be revived for groups for which more sophisticated approaches, such as total‐evidence dating, are currently infeasible. Although minimum age trees do not provide mean estimates for the age of a group, they hold a lot of information in their own right and allow the testing of various hypotheses from the areas of biogeography and co‐evolution, while avoiding reliance on ad hoc assumptions about calibration densities.

中文翻译：

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昆虫的年龄和最低年龄树的复兴

迄今为止，从化石中得出节点标定仍然是将绝对时标附加到分子树上的最常用方法。但是这种“节点定年”方法存在一个可信度问题：使用相同分子数据甚至同一组化石的不同研究，经常得出的年龄估计差异很大。造成这些差异的主要原因是众所周知的：即使年代久远，位置牢固的化石也只能为特定节点提供最小年龄。另一方面，众所周知，该节点与化石之间的时间差（或换句话说：进化枝的起源与其在化石记录中首次出现之间的时间差）非常难以量化。以有关昆虫生命树年龄的最新研究为例，我讨论了基于化石选择校准先验的不同原理，并认为它们都不是完全令人信服的。因此，我建议将节点约会分析的目标移回以科学上合理的方式可以实现的目标：一棵过时的树，反映其组成分类单元的最小年龄。尽管对时间树的这种解释在分子测年的早期被广泛采用，但它的概念优势似乎比那些允许整合更复杂的节点年龄约束的方法的承诺受到了抑制，即使这些条件难以证明是正确的。我认为，对于目前尚无法使用更复杂的方法（如总证据测年）的人群，应恢复“最小年龄树”。尽管最低年龄树无法提供一组年龄的平均值，关于校准密度的特殊假设。