The disproportionately high appearance of polydactylism among the amish suggests that a.. it is a common mutation. b.. it is a common birth defect in pennsylvania. c.. it was overrepresented in the gene pool of the original amish settlers. d.. humans are prone to this birth defect

C.

Marriages within stable geographical communities and the influx of few converts restricts the genetic pool of Amish society. Marriages sometimes occur between second cousins. Such intermarriage does not always produce medical problems. When unique recessive traits are common in a closed community certain diseases simply are more likely to occur. On the other hand, a restricted gene pool may offer protection from other hereditary diseases.