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

Any physical contact between the members of the same species including contact mediated, e.g., by insects transferring pollen, exposes the organisms to the risk of parasitism (Hastings 1999).In this aspect, sexual reproduction is frequently the Achilles heel of organisms. The transfer of a parasite or other infectious agent need not occur during the actual act of sexual reproduction.Sexually reproducing organisms cannot live in isolation; the members of the same species must stay together for at least part of their lives, creating suitable preconditions for transfer of infection.

            Parasite – host interactions and the phenomenon of parasitism is probably a factor with greatly underestimated importance in biological evolution.Adaptation of living organisms to a change in abiotic factors is a relatively simple, one-step matter.An abiotic environment does not actively resist evolution.If, for example, a species adapts to increased temperature of the local climate modifying its metabolism or its behaviour, the environment will not “spoil” this by reacting with a further increase in the temperature of the local climate.In contrast, the mutual interactions between organisms frequently have the character of a sort of evolutionary “arms race”.Every new evolutionary feature on the part of a parasite leads to selection pressure on the creation of a counter measure on the part of the host.These arms races, although they may not be the main motor, are certainly the main content of the activities of biological evolution.Very complicated adaptations emerge in this arms race and any structure or pattern of behaviour affecting the result of the parasite – host interaction, i.e. also sexual reproduction, is most certainly a subject of intense natural selection.