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Evolutionary layering and the limits to cellular perfection

机译：进化分层和细胞完善的局限性

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摘要

Although observations from biochemistry and cell biology seemingly illustrate hundreds of examples of exquisite molecular adaptations, the fact that experimental manipulation can often result in improvements in cellular infrastructure raises the question as to what ultimately limits the level of molecular perfection achievable by natural selection. Here, it is argued that random genetic drift can impose a strong barrier to the advancement of molecular refinements by adaptive processes. Moreover, although substantial improvements in fitness may sometimes be accomplished via the emergence of novel cellular features that improve on previously established mechanisms, such advances are expected to often be transient, with overall fitness eventually returning to the level before incorporation of the genetic novelty. As a consequence of such changes, increased molecular/cellular complexity can arise by Darwinian processes, while yielding no long-term increase in adaptation and imposing increased energetic and mutational costs.
机译：尽管从生物化学和细胞生物学获得的观察结果似乎说明了数百种分子适应性的例子，但是实验操作常常可以改善细胞基础设施这一事实提出了一个问题，即最终限制了自然选择可以达到的分子完善水平。在这里，有人认为随机遗传漂移会通过适应性过程对分子提纯的发展施加强大的障碍。此外，尽管有时可以通过出现对先前建立的机制进行改善的新型细胞特征来实现对适应性的实质性改善，但预计这种进展通常是短暂的，总体适应性最终会恢复到纳入遗传新奇性之前的水平。这些变化的结果是，达尔文过程可能会增加分子/细胞的复杂性，而适应性不会长期增加，并且精力和突变成本也会增加。

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