In many species, the production of migrants is a costly investment that may not seem very efficient. Many migrants die without offspring, many reach locations that are less favourable in terms of chances for survival. Hamilton (Hamilton & May 1977; Comins, Hamilton, & May 1980) (Fig. VII.2) suggested reasons why many species nevertheless invest a large part of their reproduction potential into producing migrants. By moving farther away from their parents, migrants reduce the chance of offspring competing with their own family. This situation is extremely beneficial from the point of view of individual inclusive fitness. Thus, an allele “programming” its bearer to produce primarily migrants will be preferred in interallelic competition over an allele reducing the number of migrants produced in favour of production of non-migrant offspring. Another advantage of investing in migrants lies in the fact that migrants have a non-zero chance of reaching an unoccupied location and also in the exponential rise of the newly established population producing more offspring in subsequent generations than the non-migrating individuals under the possibly better conditions in the territory of the parent sub-population, which, however, is already occupied by the species.