The Dunkers is a religious group which moved from Germany to Pennsylvania in the 1700's. The Dunkers do not mate outside of their small group, and this has led to a change in the frequency of certain genes. The Pennsylvania Dunkers are now unique for other populations, including their German relatives. Which of these best describes this occurred?

Because the situation above describes a small population that does not mate with those who are outside their group, we can say that they reflect a small population with no migration or immigration. It's as if they live and act in isolation from other populations. One result of this set-up is genetic drift or the change in allele frequency of the genes currently present in the gene pool. Reproduction within the small group may further result to inbreeding, which can also lead ultimately to genetic drift.