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A Neglected Dimension of Evolution and the Origin of Species

机译：被忽视的进化维度和物种起源

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Some of Darwin's crucial views and ideas have been refuted by his followers in the 20th century.In this essay,I will first discuss how one of the centerpieces of Darwin's theory,the Principle of Divergence,a theory in which Darwin himself expressed "very great confidence",fared in the last century.I will then argue for the importance of linkage,a prominent factor of evolution that has been largely neglected in modern evolutionary theory.I propose that there is now sufficient evidence suggesting that linkage should be added to the list of evolutionary forces.This essential and general yet longneglected factor constitutes an intrinsic isolating mechanism of evolution (referred to as ‘genealogical isolation'),constituting a key principle for understanding speciation andthe inevitable discontinuities of life forms in the hierarchical biological system.Moreover,linkage can form a theoretical mechanism for Darwin's Principle of Divergence.Multiple genetic variations in gene(s) that are strongly linked can be inherited as a single unit along genealogical lineages,a phenomenon referred to as the ‘block transmission' of genetic variation.A greater understanding of this characteristic of variation and inheritance may shed light on several puzzles currently facing evolutionary biologists.First,block transmission suggests that gaps among species are the inevitable results of evolution stemming from within-species divergence; therefore,the lack of immediate transitional forms would be expected as largely natural and not entirely due to the incompleteness of the fossil record.Second,geographical isolation is not a prerequisite for speciation since genealogical isolation,despite interbreeding,is inevitable.Consequently,the primary obstacle to sympatric speciation disappears.Third,any gene,if obtaining a selective advantage following accumulation of mutations,can act as a speciation gene,if it is physically or functionally linked to another gene,which subsequently builds up mutation(s) leading to incompatibility.Thus,universal speciation gene does not exist.Reproductive isolation is a by-product of evolution due to mutations causing incompatibility either physiologically,ecologically or behaviorally.Fourth,the presence of extensive genetic polymorphism in natural populations may be due to various levels of buffering effects that offset the deleterious nature of mutations.This makes many mutations appear effectively neutral,or nearly neutral.Therefore,most mutations are probably not predetermined at birth to have an inherent nature that is neutral,beneficial or deleterious.Rather,their nature largely depends on their context,defined by genetic background,physiological states,ecological conditions,and other variables.The deductions outlined in this essay are rather preliminary.However,our hypotheses are falsifiable since they allow many predictions to be made,and,importantly,they are consequently amenable to rigorous testing.
机译：达尔文的一些批判性观点和思想在20世纪遭到了他的追随者的反驳。在本文中，我将首先讨论达尔文理论的核心内容之一-发散原理，达尔文本人表达的这一理论“非常伟大”。信心”，这在上个世纪就已经存在。然后，我将探讨连锁的重要性，连锁是现代进化论中已被很大程度上忽略的重要进化因素。我提议，现在有足够的证据表明连锁应该被添加到进化力列表。这个必不可少且普遍但长期以来被忽略的因素构成了进化的内在隔离机制（称为``遗传隔离''），构成了理解物种形成和分级生物系统中生命形式不可避免的不连续性的关键原理。连锁可以形成达尔文发散原理的理论机制。甘氨酸链可以沿着家谱世系作为一个单元遗传，这种现象被称为遗传变异的``阻断传递''。对变异和遗传特征的更深入了解可能为目前进化生物学家面临的若干难题提供了启示。块传播表明物种间的差异是种内差异导致进化的必然结果。因此，人们认为缺乏直接的过渡形式在很大程度上是自然的，而不是完全由于化石记录的不完整。第二，地理隔离并不是物种形成的先决条件，因为族谱隔离（尽管是近亲繁殖）是不可避免的。第三，任何基因，如果在突变积累后获得选择优势，则可以作为物种形成基因，如果它在物理上或功能上与另一个基因相连，则随后会形成导致不相容性的突变。因此，不存在通用的物种形成基因。生殖分离是进化的副产品，是由于突变引起的生理，生态或行为失配。第四，自然种群中广泛遗传多态性的存在可能是由于不同水平的缓冲作用所致。抵消了突变的有害性质的影响。这使得许多突变出现了效果因此，大多数突变在出生时可能并未预先确定为具有中性，有益或有害的内在本质。相反，其性质很大程度上取决于其背景，具体取决于遗传背景，生理状态，生态条件本文中概述的推论是相当初步的。但是，我们的假设是可以证伪的，因为它们可以做出许多预测，因此重要的是，这些假设可以接受严格的测试。

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