To geneticists, the polygamous Fundamentalist Church of Jesus Christ of Latter Day Saints (FLDS) community, based in West Texas, might look a bit like an eddy in the river of gene flow.
Within this sect, for generations, a small number of families have married and remarried, their genes becoming subtly more similar with each passing decade.
Now, state officials have begun gathering DNA samples from the more than 400 children taken into state custody, primarily to help tease out the complex family trees within the group and determine whether sexual abuse has taken place.
But through these tests, officials may also get a glimpse of exactly how genetically similar the individuals that make up the group have become — and why the members of this sect appear to have largely sidestepped the archetypical deformities that come part and parcel with close inbreeding.
Martha Bradley is a sociologist at the University of Utah in Salt Lake City and author of the book "Kidnapped From That Land," which documents the government's 1953 raid on a polygamous fundamentalist community in Short Creek, Ariz. She is also an expert on the FLDS, having studied the group in the early 1990s, and she believes it is likely that some degree of inbreeding has already occurred within the sect.
"I wouldn't be surprised if there were [inbreeding]," Bradley says. "It's such a small pool of members, and it has been since the '20s."
Yet, in a community roster that contains hundreds of names — but remarkably few different surnames — some wonder why the more obvious physical defects associated with inbreeding, such as cleft palate and encephalopathy, have not yet manifested themselves in the appearance of the sect members.
The answer — give it many more generations. So says Jonathan Turner, a professor of sociology at the University of California, Riverside.
"They look fine," says Turner, along with his wife Alexandra Maryanski, a co-author of "Face to Face: Toward a Sociological Theory of Interpersonal Behavior."
"You do have a relatively small breeding population, but it has not been that long," he says. "You had a fairly diverse pool to start with, so only if that went on for a long time within this same population would you see real effects.
"Now, if you went down several generations to where people lost track of who was marrying whom, you might start to see the same kinds of problems you see with [marriage between] first cousins."
Incest Taboo Keeps Inbreeding in Check
Another feature of the sect that has likely helped members avoid the problems associated with inbreeding is the incest taboo — no marriage or sexual relations between fathers and daughters or brothers and sisters, for example.
Bradley says this prohibition is observed within FLDS — though she adds that the group does not keep an official database to explicitly prevent unions between members who were related at some level.
Turner is not surprised that such a prohibition was in place, considering the religious nature of the sect. But he says other factors could also be at play which would encourage the occasional introduction of new genes into the rarified pool. Movement of members between communities within the sect could "reshuffle the deck" when it comes to genes, further reducing the likelihood of some of the more severe effects of inbreeding.
This, combined with observance of the incest taboo, could offer enough diversity to sidestep major problems.
"A lot of people may share one-eighth or one-sixteenth of their genes, which probably doesn't create big problems," Turner says. "When you share 25 to 50 percent of your genes, that's when you start to get abnormalities."
Inbreeding May Still Leave a Mark
But just because the more overt evidence of inbreeding within the group has not yet surfaced, it does not necessarily mean that the group is untouched by the problem.
"There were frequent cases when first cousins married each other," Bradley says. "When you think of the complexity of the family situation, almost everyone is related to everyone else in the society at some level."
In his past research, Mark Leone, a professor of sociology at the University of Maryland, showed that more subtle health effects, including nearsightedness and mental problems, could be seen in some isolated groups in which inbreeding was known to have occurred.
And Bradley notes that a further narrowing of genetic diversity within the group may accompany another practice that has been seen within FLDS — a skewing of the male to female ratio.
"When I did my work in the early '90s, it was pretty close to 50-50," she says. "But increasingly in the last five years, these groups have been sending young boys out of the community. They're essentially getting rid of competition."