This argument implies that evolution can only occur if mutant mates cannot be avoided, as a result of a severe scarcity of potential mates. This is most likely to occur in small, isolated communities. These occur most commonly on small islands, in remote valleys, lakes, river systems, or caves, or during the aftermath of a mass extinction. Under these circumstances, not only is the choice of mates severely restricted but population bottlenecks, founder effects, genetic drift and inbreeding cause rapid, random changes in the isolated population's genetic composition. Furthermore, hybridization with a related species trapped in the same isolate might introduce additional genetic changes. If an isolated population such as this survives its genetic upheavals, and subsequently expands into an unoccupied niche, or into a niche in which it has an advantage over its competitors, a new species, or subspecies, will have come into being. In geological terms, this will be an abrupt event. A resumption of avoiding mutant mates will thereafter result, once again, in evolutionary stagnation.
this argument implies that evolution can only occur if mutant mates cannot be avoided as a result of a severe scarcity of potential mates this is most likely to occur in small isolated communities these occur most commonly on small islands in remote valleys lakes river systems or caves or during the aftermath of a mass extinction under these circumstances not only is the choice of mates severely restricted but population bottlenecks founder effects genetic drift and inbreeding cause rapid random changes in the isolated population's genetic composition furthermore hybridization with a related species trapped in the same isolate might introduce additional genetic changes if an isolated population such as this survives its genetic upheavals and subsequently expands into an unoccupied niche or into a niche in which it has an advantage over its competitors a new species or subspecies will have come into being in geological terms this will be an abrupt event a resumption of avoiding mutant mates will thereafter result once again in evolutionary stagnation