Many hypotheses have been proposed for how sexual reproduction may facilitate an increase in the population mean fitness, such as the Fisher-Muller theory, Muller’s ratchet and others. According to the recently proposed mixability theory, however, sexual recombination shifts the focus of natural selection away from favoring particular genetic combinations of high fitness towards favoring alleles that perform well across different genetic combinations. Mixability theory shows that, in finite populations, because sex essentially randomizes genetic combinations, if one allele performs better than another across the existing combinations of alleles, that allele will likely also perform better overall across a vast space of untested potential genotypes. However, this superiority has been established only for a single-locus diploid model. We show that, in both haploids and diploids, the power of randomization by sex extends to the multilocus case, and becomes substantially stronger with increasing numbers of loci. In addition, we make an explicit comparison between the sexual and asexual cases, showing that sexual recombination is the cause of the randomization effect. That the randomization effect applies to the multilocus case and becomes stronger with increasing numbers of loci suggests that it holds under realistic conditions. One may expect, therefore, that in nature the ability of an allele to perform well in interaction with existing genetic combinations is indicative of how well it will perform in a far larger space of potential combinations that have not yet materialized and been tested. Randomization plays a similar role in a statistical test, where it allows one to draw an inference from the outcome of the test in a small sample about its expected outcome in a larger space of possibilities—i.e., to generalize. Our results are relevant to recent theories examining evolution as a learning process. This article was reviewed by David Ardell and Brian Golding.

中文翻译：

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多位点遗传进化中性别随机化的力量

已经提出了许多关于有性生殖如何促进种群平均适应度增加的假设，例如 Fisher-Muller 理论、Muller 棘轮理论等。然而，根据最近提出的混合性理论，性重组将自然选择的重点从偏爱高适应性的特定遗传组合转移到偏爱在不同遗传组合中表现良好的等位基因。混合性理论表明，在有限种群中，因为性别本质上是随机化遗传组合，如果一个等位基因在现有等位基因组合中的表现优于另一个等位基因，则该等位基因也可能在未经测试的潜在基因型的广阔空间中整体表现更好。然而，这种优势仅在单基因座二倍体模型中建立。我们表明，在单倍体和二倍体中，按性别随机化的能力扩展到多基因座的情况，并且随着基因座数量的增加而变得更加强大。此外，我们对有性和无性病例进行了明确的比较，表明性重组是随机效应的原因。随机化效应适用于多基因座情况，并且随着基因座数量的增加而变得更强，这表明它在现实条件下成立。因此，人们可能会预期，在自然界中，等位基因与现有基因组合相互作用良好的能力表明它在尚未实现和测试的潜在组合的更大空间中的表现如何。随机化在统计检验中扮演着类似的角色，它允许人们从小样本的测试结果中推断出更大的可能性空间中的预期结果——即概括。我们的结果与最近将进化视为学习过程的理论相关。本文由 David Ardell 和 Brian Golding 审阅。