 A recently observed example has as protagonists M.xanthus (predator) and E.coli (prey) in which a parallel evolution of both species can be observed through genomic and phenotypic modifications, producing in future generations a better adaptation of one of the species that is counteracted by the evolution of the other, thus generating an arms race that can only be stopped by the extinction of one of the species.A competing evolutionary idea is the court jester hypothesis, which indicates that an arms race is not the driving force of evolution on a large scale, but rather it is abiotic factors.The Black Queen Hypothesis is a theory of reductive evolution that suggests natural selection can drive organisms to reduce their genome size.