THE MOLECULAR CLOCK RUNS MORE SLOWLY IN MAN THAN IN APES AND MONKEYS
THE MOLECULAR CLOCK RUNS MORE SLOWLY IN MAN THAN IN APES AND MONKEYS
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DOI：
10.1038/326093a0
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发表时间：
1987-03-05
期刊：
影响因子：
64.8
通讯作者：
TANIMURA, M
中科院分区：
文献类型：
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作者：
LI, WH;TANIMURA, M
分子钟假说1假设分子进化的速率随着时间的推移大致恒定。尽管这一假设在过去备受争议，但现在已被广泛接受2-5。速率恒定性的假设通常被视为重建生物体或基因之间的系统发育关系以及确定进化事件年代的基础2-5。此外，它被视为对中性突变假说的有力支持，该假说假设进化中的大多数分子变化是由于中性或近中性突变造成的。由于这些原因，速率恒定性假设的有效性是分子进化中的一个重要问题。最近使用 DNA 序列数据进行的研究 7-12 对这一假设提出了严重怀疑。这些研究为免疫学距离和蛋白质序列数据13,14提出的建议提供了支持，即类人猿进化速度已经放缓，并且与DNA杂交研究15,16一致，啮齿类动物的核苷酸取代率明显高于人类。据估计，啮齿类动物的核苷酸取代率比高等灵长类动物高 4-10 倍，比偶蹄类动物高 2-4 倍。此外，这项研究为人科动物减速假说提供了强有力的证据13,14，并表明人科动物进化速度进一步放缓。我们的结果表明，哺乳动物之间的速率差异主要是由于世代时间的差异8,16，而不是DNA修复机制的变化9。我们还提出了一种在违反速率恒定性假设时估计物种之间的分歧时间的方法。
The molecular clock hypothesis1postulates that the rate of molecular evolution is approximately constant over time. Although this hypothesis has been highly controversial in the past, it is now widely accepted2–5. The assumption of rate constancy has often been taken as a basis for reconstructing the phylogenetic relationships among organisms or genes and for dating evolutionary events2–5. Further, it has been taken as strong support for the neutral mutation hypothesis5, which postulates that the majority of molecular changes in evolution are due to neutral or nearly neutral mutations6. For these reasons, the validity of the rate constancy assumption is a vital issue in molecular evolution. Recent studies7–12using DNA sequence data have raised serious doubts about the hypothesis. These studies provided support for the suggestion made from immunological distance and protein sequence data13,14that a rate slowdown has occurred in hominoid evolution, and showed, in agreement with DNA hybridization studies15,16, that rates of nucleotide substitution are significantly higher in rodents than in man. Here, rates of nucleotide substitution in rodents are estimated to be 4–10 times higher than those in higher primates and 2–4 times higher than those in artiodactyls. Further, this study provides strong evidence for the hominoid slowdown hypothesis13,14and suggests a further rate-slowdown in hominoid evolution. Our results suggest that the variation in rate among mammals is primarily due to differences in generation time8,16rather than changes in DNA repair mechanisms9. We also propose a method for estimating the divergence times between species when the rate constancy assumption is violated.