An island may be colonised by just a few individuals, or just a pair:, or even a single gravid female. When a new population develops from these early colonisers of the island, they undergo drastic genetic repatterning. This is sonletirnes described as a genetic revolution. The founder being small in number, the first major change in the colonisers is a drastic reduction in the variability. Inbreeding further reduces variability. Inbreeding eliminates recessives as homozygotes and the genetic load is reduced. The decisive change is from a large open population to a small closed population. In the closed population, overdominance, that is the superior fitness of the heterozygote (say, Aa) over the other two homozygotes (AA and aa), increases. Non-allelic epistatic interactions of genes greatly alter the functioning of the gene complexes. As a result the genetic cohesiveness is broken and the founder population becomes plastic and pliable enough to be moulded into a newer one with better adaptations. This, in essence, is the genetic repatterning or the genetic revolution.