Aging – a strategy to fight parasites?

"War" with parasites may be the cause of aging

Ilya Vedmedenko, Naked Science

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 that lead to wear and tear of the body;

– mutations, failures and deterioration of the "repair" abilities of cells.

According to a number of scientists, aging is designed to give evolutionary advantages to the species. But how is this achieved?

The American scientist Richard Y. Chin presented his conclusions on this matter. The researcher applied the so - called the hypothesis of the Black Queen 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 fittest descendants appear. They can fight parasites and infections more effectively, which ultimately allows the species to confidently maintain its niche in the ecosystem.

Richard Chin has created a computer model that shows the dynamics of populations of parasites and their hosts over one five-hundred-year cycle. In each population there were 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 remaining one (Chin distributed these relationships between phenotypes randomly). In total, the model had 1000 cycles. Richard Chin tested the dynamics of populations with several variants of the onset of host aging: 2, 5, 10 and 20 years.

The deceased organism was replaced by another one possessing 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 parasite damage to the population and the rate of reproduction, which were initially established.

The model showed that with the shortest life span 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 consider 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 organisms.

The article Aging As A Defense Strategy Against Parasites is published in the journal of bioRxiv preprints.

Portal "Eternal youth" http://vechnayamolodost.ru  17.07.2017