An evolutionary "arms race" between parasites and their carriers was named as one of the possible causes of aging.
Until now, scientists do not have a common understanding of why species (including humans) age and die. Most often this is associated with two aspects:
- genetic or epigenetic programs leading to wear and tear of the body;
- mutations, failures and deterioration of the "repair" ability of cells.
According to a number of scientists, aging is intended to give evolutionary advantages to a species. But how is this achieved?
American scientist Richard Y. Chin presented his conclusions on this score. The researcher applied the so-called. the Black Queen's hypothesis to explain sexual reproduction and the evolutionary "arms race" of parasites and their carriers. The microevolutionary version of the hypothesis suggests that when the genes of the mother and father are mixed, the most adapted offspring appear. They can fight parasites and infections more effectively, which ultimately allows the species to confidently maintain its niche in the ecosystem.
Richard Chin created a computer model that shows the dynamics of populations of parasites and their hosts over one five-hundred-year cycle. Each population contained 100 organisms with three host phenotypes and three parasite phenotypes. Each of the host phenotypes showed resistance to one of the three parasite phenotypes, partial resistance to the other, and susceptibility to the rest (Chin randomly distributed these relationships between phenotypes). In total, the model consisted of 1000 cycles. Richard Chin tested the dynamics of populations under several variants of the beginning of the aging of the host: 2, 5, 10 and 20 years.
The deceased organism was replaced by another one with one of several phenotypes. His choice was determined by the distribution of all three phenotypes in the previous period. The latter, in turn, was determined by the level of infestation of the population by parasites and the rate of reproduction, which were established initially.
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The model showed that with the shortest lifespan of a single individual, the population demonstrates the best ability to resist parasites. If we assume that sexual reproduction has developed as a way of cyclical change of alternative host phenotypes of resistance to parasites, then aging increases the efficiency of this process. And if we take into account that in many species aging and sexual reproduction are closely related, and the development of these traits could go on simultaneously, then it is likely that they evolved in response to the same evolutionary pressure - interaction with parasites. Thus, Richard Chin concludes that the fight against "uninvited guests" is one of the main causes of aging of organisms.
Ilya Vedmedenko
