Frozen Evolution. Or, that’s not the way it is, Mr. Darwin. A Farewell to Selfish Gene.

An important mechanism enabling an increase in the chance of transmission of a parasite between hosts consists in inducing behavioral changes in the infected host that can positively affect the probability of transmission of a parasite from one host to another (Barnard & Behnke 1990; Moore 1984).The parasite can cause these changes in various ways.The most specific mechanisms include direct intervention in the central nervous system of the host, through which the parasite is even capable of initiating very complicated patterns of behavior.The simplest mechanisms, on the other hand, encompass unspecific pathogenic effects on the host organism that, while they reduce the vitality of the host and thus increasethe chance that the parasite will kill its host and die itself, also can be very functional for the parasite in some special cases, from the standpoint of its transmission in the host population.The types of behavioral changes that the parasite induces depend primarily on the mechanism of its transmission.It is understandable that the behavioral changes that assist in transmission from an intermediate host to the definitive host through predation are completely different from changes that increase the effectiveness of transmission of sexually transmitted parasites.