Kimura M
National Institute of Genetics, Mishima, Japan.
Genome. 1989;31(1):24-31. doi: 10.1139/g89-009.
The main tenet of the neutral theory is that the great majority of evolutionary changes at the molecular level are caused not by Darwinian selection but by random fixation of selectively neutral (or very nearly neutral) alleles through random sampling drift under continued mutation pressure. The theory also asserts that the majority of protein and DNA polymorphisms are selectively neutral, and that they are maintained in the species by mutational input balanced by random extinction rather than by "balancing selection." The neutral theory is based on simple assumptions. This enabled us to develop mathematical theories (using the diffusion equation method) that can treat these phenomena in quantitative terms and that permit theory to be tested against actual observations. Although the neutral theory has been severely criticized by the neo-Darwinian establishment, supporting evidence has accumulated over the last 20 years. In particular, the recent burst of DNA sequence data helped to strengthen the theory a great deal. I believe that the neutral theory triggered reexamination of the traditional "synthetic theory of evolution." In this paper, I review the present status of the neutral theory, including discussions of such topics as "molecular evolutionary clock," very high evolutionary rates observed in RNA viruses, a deviant coding system found in Mycoplasm together with the concept of mutation-driven neutral evolution, and the origin of life. I also present a worldview based on the conception of what I call "survival of the luckiest."
中性理论的主要宗旨是，分子水平上绝大多数的进化变化并非由达尔文选择引起，而是在持续的突变压力下，通过随机抽样漂变使选择性中性（或非常接近中性）的等位基因随机固定所致。该理论还断言，大多数蛋白质和DNA多态性是选择性中性的，并且它们在物种中通过随机灭绝所平衡的突变输入得以维持，而非通过“平衡选择”。中性理论基于简单的假设。这使我们能够发展出数学理论（使用扩散方程方法），可以从数量上处理这些现象，并允许将理论与实际观测进行对比验证。尽管中性理论受到了新达尔文主义学派的严厉批评，但在过去20年里支持性证据不断积累。特别是，最近涌现的DNA序列数据极大地强化了该理论。我认为中性理论引发了对传统“进化综合理论”的重新审视。在本文中，我回顾中性理论的现状，包括对诸如“分子进化时钟”、在RNA病毒中观察到的极高进化速率、在支原体中发现的异常编码系统以及突变驱动的中性进化概念，还有生命起源等主题的讨论。我还基于我所谓的“最幸运者生存”概念提出一种世界观。
