closed communities because they inter-marry.
Amish suffer genetic problems for a few reasons:
Small founding groups-individual Amish communities typically originate from relatively few families. Almost all of the Amish in Lancaster County, for example, originated from a few dozen 18th-century immigrant families.
Genetic isolation-converts to the Amish have been rare, and Amish only marry other Amish. This practice of endogamy, with few new bloodlines entering the population, has led to limited variation of genes.
These two factors combine to create a “founder effect”. A founder effect means that genetic variation is lost over time due to a limited number of founding individuals. Certain recessive traits found in a small founding population are amplified in future generations.
Amish face a particular challenge. The Amish way of life and culture, requiring members to restrict use of technology, live in a generally austere manner, and master a specific dialect for worship and day-to-day communication, makes it particularly difficult for non-Amish to join the Amish church.
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