Bernstein H, Byerly H C, Hopf F A, Michod R E
J Theor Biol. 1984 Oct 5;110(3):323-51. doi: 10.1016/s0022-5193(84)80178-2.
The competitive advantage of sex consists in being able to use redundancy to recover lost genetic information while minimizing the cost of redundancy. We show that the major selective forces acting early in evolution lead to RNA protocells in which each protocell contains one genome, since this maximizes the growth rate. However, damages to the RNA which block replication and failure of segregation make it advantageous to fuse periodically with another protocell to restore reproductive ability. This early, simple form of genetic recovery is similar to that occurring in extant segmented single stranded RNA viruses. As duplex DNA became the predominant form of the genetic material, the mechanism of genetic recovery evolved into the more complex process of recombinational repair, found today in a range of species. We thus conclude that sexual reproduction arose early in the evolution of life and has had a continuous evolutionary history. We cite reasons to reject arguments for gaps in the evolutionary sequence of sexual reproduction based on the presumed absence of sex in the cyanobacteria. Concerning the maintenance of the sexual cycle among current organisms, we take care to distinguish between the recombinational and outbreeding aspects of the sexual cycle. We argue that recombination, whether it be in outbreeding organisms, self-fertilizing organisms or automictic parthenogens, is maintained by the advantages of recombinational repair. We also discuss the role of DNA repair in maintaining the outbreeding aspects of the sexual cycle.
性别的竞争优势在于能够利用冗余来恢复丢失的遗传信息，同时将冗余成本降至最低。我们表明，在进化早期起作用的主要选择力量导致RNA原始细胞的出现，其中每个原始细胞包含一个基因组，因为这样能使生长速率最大化。然而，RNA的损伤会阻止复制，且分离失败，这使得与另一个原始细胞定期融合以恢复繁殖能力变得有利。这种早期、简单的基因恢复形式类似于现存的分段单链RNA病毒中发生的情况。随着双链DNA成为遗传物质的主要形式，基因恢复机制演变成了如今在一系列物种中发现的更复杂的重组修复过程。因此，我们得出结论，有性生殖在生命进化早期就已出现，并且有着连续的进化历史。我们列举了一些理由，以驳斥基于假定蓝藻中不存在有性生殖而提出的有性生殖进化序列存在缺口的观点。关于当前生物体中有性生殖周期的维持，我们谨慎地区分了有性生殖周期中的重组和远交方面。我们认为，无论是在远交生物体、自体受精生物体还是兼性孤雌生殖体中，重组都是由重组修复的优势所维持的。我们还讨论了DNA修复在维持有性生殖周期远交方面的作用。
