Institute of Healthy Ageing, and Research Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK.
Institute of Healthy Ageing, and Research Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK.
Ageing Res Rev. 2019 Mar;50:58-71. doi: 10.1016/j.arr.2019.01.008. Epub 2019 Jan 9.
A widely appreciated conclusion from evolutionary theory is that senescence (aging) is of no adaptive value to the individual that it afflicts. Yet studies of Caenorhabditis elegans and Saccharomyces cerevisiae are increasingly revealing the presence of processes which actively cause senescence and death, leading some biogerontologists to wonder about the established theory. Here we argue that programmed death that increases fitness could occur in C. elegans and S. cerevisiae, and that this is consistent with the classic evolutionary theory of aging. This is because of the special conditions under which these organisms have evolved, particularly the existence of clonal populations with limited dispersal and, in the case of C. elegans, the brevity of the reproductive period caused by protandrous hermaphroditism. Under these conditions, death-promoting mechanisms could promote worm fitness by enhancing inclusive fitness, or worm colony fitness through group selection. Such altruistic, adaptive death is not expected to evolve in organisms with outbred, dispersed populations (e.g. most vertebrate species). The plausibility of adaptive death in C. elegans is supported by computer modelling studies, and new knowledge about the ecology of this species. To support these arguments we also review the biology of adaptive death, and distinguish three forms: consumer sacrifice, biomass sacrifice and defensive sacrifice.
从进化理论中广泛得到认可的一个结论是，衰老（老化）对于受其影响的个体没有适应价值。然而，对秀丽隐杆线虫和酿酒酵母的研究越来越多地揭示了一些积极导致衰老和死亡的过程，这使得一些生物老年学家对既定理论产生了怀疑。在这里，我们认为增加适合度的程序性死亡可能发生在秀丽隐杆线虫和酿酒酵母中，这与衰老的经典进化理论是一致的。这是因为这些生物进化的特殊条件，特别是存在克隆种群，其扩散能力有限，而且在秀丽隐杆线虫的情况下，由于雌雄同体的性成熟前现象导致生殖期短暂。在这些条件下，促进死亡的机制可以通过提高适合度，或通过群体选择提高线虫群体的适合度，从而促进线虫的适应性。这种利他的、适应性的死亡预计不会在具有杂交、分散种群的生物中进化（例如大多数脊椎动物物种）。计算机建模研究以及对该物种生态学的新知识支持了秀丽隐杆线虫中适应性死亡的可能性。为了支持这些论点，我们还回顾了适应性死亡的生物学，并区分了三种形式：消费者牺牲、生物量牺牲和防御性牺牲。
