Further reference from Straight Dope columns for additional reference:
Inbreeding in rural areas:
http://www.straightdope.com/classics/a980724.html
http://www.straightdope.com/columns/051028.html
Cousin Marriage:
http://www.straightdope.com/columns/041001.html) (Nic2004’s link)
The germ of the idea arises from the very real issue that if you are in a small, isolated rural (or insular) community, unless you have vigorous migration after a few generations everybody will be some degree of cousin to everybody else. Look up also the case of the inhabitants of isolated Pitcairn Island, all descended from a handful of HMS Bounty mutineers.
Now, what constitutes “incest” is culture-dependent(*) – and depending on the culture there are many degrees of cousinhood or nephew/niecehood that may be fair game. In many cultures “first cousins” are entirely fine and dandy as potential mates. Siince in that culture, it’s NOT “incest” to do your cousin, the problem if any is not of prevalent “incest” but of inbreeding – a depleted gene pool. You throw into that also the association of “hill people” villages with “old country” traditions or religions that promote endogamy, i.e. marriage within the group. If the group is not too big, again… This was a bigger potential problem before advances in transportation and access, when it could be a major endeavor to travel to the nearest decently-sized town and a particular valley could be cut off all through the winter or the flood season. Still, you do not need a situation of massive less-than-4th-degree-of-consanguinity pairings to cause a noticeable inbreeding effect – and NEITHER does that sort of pairing guarantee ill effects.
(which is not to say there may be social environments where what the culture itself calls incest has a higher frequency: Jerry Springer keeps finding cases of Dad/Daughter, Son/Mom, Bro/Sis, Sis/Sis, Mom/Daughter, etc. “happy couples”… but they are not necessarily from the hills and hollers, some are from in-town)
Cecil does hint, in the column on the source of social oprobium and bans upon 1st-cousin marriage, that the use of this as a stereotype put-down of rural people (and in the USA, of even not-quite-so-rural so-called “Trailer Trash” [sub]What the hell does the trailer have to do with it anyway?[/sub]) derives from a belief in the moral superiority of the urban, cosmopolitan lifestyle brought about by “progress”. It correlates with the old idea of “degeneracy”, wherein those deprived of the favorable influences of progress (or of wiser elites) will become “degenerate” and that will include their morals.
[sub](*“Incest”, traditionally, is sex between two people who due to degree of consanguinity are forbidden to mary one another; in modern times it was adjusted to refer to specific degrees in its own right. You can imagine how much that may vary in time and location. Many believe the ban, anthropologically, arose not so much to combat inbreeding as to ensure that no romantic rivalries or favoritisms will arise between people who have to maintain obligations as family/clan members, and that there will be a pool of eligible mates to marry members of other clans so as to strengthen the tribe’s bonds. Any inbreeding ill-effects would be seen as a “smiting” for violating the rule.)[/sub]
[edit at poster’s req. P.S., report a post (any post), we’re more likely to see it. --G]