Welch John J, Bromham Lindell
Centre for the Study of Evolution, School of Life Sciences, University of Sussex, Falmer, Brighton, UK, BN1 9QG.
Trends Ecol Evol. 2005 Jun;20(6):320-7. doi: 10.1016/j.tree.2005.02.007.
Molecular-dating techniques potentially enable us to estimate the time of origin of any biological lineage. Such techniques were originally premised on the assumption of a 'molecular clock'; that is, the assumption that genetic change accumulated steadily over time. However, it is becoming increasingly clear that constant rates of molecular evolution might be the exception rather than the rule. Recently, new methods have appeared that enable the incorporation of variable rates into molecular dating. Direct comparisons between these methods are difficult, because they differ in so many respects. However, the assumptions about rate change on which they rely fall into a few broad categories. Improving our understanding of molecular evolution will be an important next step towards evaluating and improving these methods.
分子年代测定技术有可能使我们估计任何生物谱系的起源时间。此类技术最初基于“分子钟”假设；也就是说，假设遗传变化随时间稳步积累。然而，越来越明显的是，恒定的分子进化速率可能是例外而非普遍规律。最近，出现了一些新方法，能够将可变速率纳入分子年代测定。由于这些方法在诸多方面存在差异，因此很难对它们进行直接比较。然而，它们所依赖的关于速率变化的假设可归为几大类。增进我们对分子进化的理解将是评估和改进这些方法的重要的下一步。
