Minorities can use it to stay ethnically homogeneous over a long time as distinct communities within societies that have other practices and beliefs.
The isolationist practices of endogamy may lead to a group's extinction, as genetic diseases may develop that can affect an increasing percentage of the population.
[1] The small community on the South Atlantic island of Tristan da Cunha are, because of their geographical isolation, an almost endogamic society.
There are instances of health problems attributed to endogamy on the island, including glaucoma and asthma as research by the University of Toronto has demonstrated.
If a cousin marriage has accrued in a known ancestral tree of a person, in historical time, it is referred to as pedigree collapse.