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

The alternation of long series of cycles of asexual reproduction with one cycle of sexual reproduction is characteristic for many groups of unicellular organisms.  During asexual reproduction, the viability of the organisms frequently decreases, i.e. the clone gradually degenerates.If we prevent organisms from reproducing sexually, they can eventually die out as a result of this degeneration.In nature, these organisms frequently undergo sexual reproduction under quite specific situations, most frequently when living conditions deteriorate, so that it can be expected that the population as a whole would die out and a new population will emerge at a different place and time from individual cells (e.g. spores).It is quite possible that the cycle of sexual reproduction involves correction of mutations that accumulated since the previous cycle of sexual reproduction, so that the subsequent population could begin “with a clean desk”.