This news article about the Fundamentalist Church of Jesus Christ of Latter Day Saints (FLDS) kills two topics with one stone.
1. The often, yet unintended, destructive effects of crazy religious beliefs.
2. Evolution in action.
This was in the news a few years ago, about this offshoot of Mormons who forced teenage girls into marriage with much older men, essentially as sex slaves. The latest result of this cult is that children born of these marriages, often between cousins, are afflicted with a genetic disorder known as fumarase deficiency. This enzyme deficiency prevents brain cells from receiving sufficient nutrition causing mental retardation, frequent epileptic seizures, episodes of coma and other problems. The extent of the problem in this particular cult in indicated by the fact that half of the worlds known cases are in one particular town in Arizona, where this cult was situated.
Local historian Benjamin Bistline said 75 to 80 percent of people in the area are blood relatives of two men — John Y. Barlow and Joseph Smith Jessop — who founded the sect on the remote desert plateau in the early 1930s.
The irony here is that this sect, like most fundamentalist cults based on a strict biblical adherence, most likely scoffs at evolution. But most evolutionary biologists would probably agree that incest is a taboo across almost all cultures, precisely because in our evolutionary history, humans discovered that too much inbreeding weakened the population. The chance of passing on defective genes multiplies when relatives reproduce, because the mutated gene may be present in both parents, thereby increasing the odds of it being passed to the next generation.
Interesting explanation of the adaptive incest avoidance mechanisms here.
So what we are looking at is evolution in action. Take that, Ken Ham!