Aging as a defense strategy against parasites

The teleology of aging has been one of the more vexing and controversial question in biology. One potential evolutionary driver of programmed aging is selection pressure from parasites and other infectious organisms. While selection pressure from parasites and other infectious organisms have long been considered by many biologists to have led to the evolution of sexual reproduction, it has only rarely been considered as a potential driver for evolution of aging, a biological process that likely evolved contemporaneously with sexual reproduction. Here I describe stochastic simulations of host and parasite populations with senescence as an independent variable. The results show that populations with more rapid senescence bear lower parasite loads and oscillate more quickly through alternate phenotypes with differential resistance against parasites. I conclude that programmed aging and death may promote host evasion of parasites in a co-evolutionary competition against parasites.