The Samaritans are a fascinating people. Once a group that numbered up to a million people in late Roman times, the Samaritan population is now just over 700. I found this information about the dilemma of Samaritan continuity very interesting:
One of the biggest problems facing the community today is the issue of continuity. With such a small population, divided into only four families (Cohen, Tsedakah, Danfi and Marhib; a fifth family died out in the last century) and a general refusal to accept converts, there has been a history of genetic disease within the group due to the small gene pool. To counter this, the Samaritan community has recently agreed that men from the community may marry non-Samaritan (primarily, Israeli Jewish) women, provided that the women agree to follow Samaritan religious practices. There is a six-month trial period prior to officially joining the Samaritan community to see whether this is a commitment that the woman would like to take. This often poses a problem for the women, who are typically less than eager to adopt the strict interpretation of Biblical (Levitical) laws regarding menstruation, by which they must live in a separate dwelling during their periods and after childbirth. Nevertheless, there have been a few instances of intermarriage. In addition, all marriages within the Samaritan community are first approved by a geneticist at Tel HaShomer Hospital, in order to prevent the spread of genetic disease. In meetings arranged by "international marriage agencies," a small number of Ukrainian women have recently been allowed to marry into the community in an effort to expand the gene pool.