Among the Old Order Amish of Lancaster, Pennsylvania, there is an unusually high frequency of polydactylism (extra fingers). Since the group was founded by a small group of separatist German Mennonites in the early 1770s, some 61 cases of this rare trait have been reported, about as many cases as in the entire rest of the world since that time. Given that the trait is inherited, how can you explain the high frequency of this trait among the Old Order Amish

A founder effect

Explanation:

A founder effect is a genetic phenomenon caused by genetic drift (i.e., fixation of alleles due to random sampling). A funder effect occurs when a small group of individuals separates from an original population. Due to this separation, some randomly sampled alleles are fixed in the new population, while many other alleles are lost from the original population. Polydactylism is a trait caused by the inheritance of a dominant allele. In this case, it is expected that the frequency for this allele was increased in the original group of separatist German Mennonites, thereby increasing the frequency of the trait in the new population.