In Cecil’s column on inbreeding, there was a comment I didn’t really understand:
What amount of inbreeding can be accounted for by chance? What statistical method is used to account for inbreeding?
I assume that, in a given population, a certain number of people are going to breed. (Damn breeders!) With a small population there will be more chance of inbreeding. But, how does one determine what level of inbreeding will occur by chance in the entire population?
How many people are in your range of meeting folks (your city, or your town, or your school, or whatever)? How many of those are your cousin (to whatever degree we’re using as the standard of inbreeding)? The latter number over the former would be the chance level of inbreeding. Or at least, so I presume: It seems pretty straigtforward to me.
welcome to tennessee. 
If you never really leave the area where your family is and you have astranged family I guess that it’s very possible to marry your cousin.
There are also a lot of adopted kids out there. Isn’t this the reason for the blood test for people getting married?
The 2 blood tests I know about associated with marriage are the Wasserman, for a venerial disease, and a blood typing test. At least that is what our state requires, and I had no problem taking. Keep in mind the blood testing thingy seriously predates DNA typing…
Nope. When blood tests were required, and most (if not all states) no longer require them, it was to screen for untreated syphilis, which can cause congenital abnormalities in infants whose mothers have the disease.
The programs were discontinued after it was determined that it took a few million dollars worth of tests to discover one case of untreated syphilis in folks who were applying for a marriage license.
And also to test for (as noted by aruqvan) RH factor incompatability, which also can cause problem pregnancies. However, since RH screening is standard for pre-natal care, there was really no point to require it for a marriage license either.
=) was married 14 years ago - no clue if they still test or not … probably still do - connecticut still has colonial laws still on the books =)
See Cecil’s column on the subject: What is the purpose of premarital blood testing?
They still do, for syphillis. The test takes at LEAST a week to come back, is not covered by insurance, and is in addition to the $70 (approx) fee for the license.
This is why DrLoveGun and I scampered off to NYC, a mere half hour away, where a license could be had for $35 and they left our blood alone.
I know first cousins that had a child together. He is 14 now. Yep, Grandmas’ are sisters. And this is in a “blue state”! :smack:
I think what Cecil was getting at was that we’re all cousins, so the average degree of consanguinuity is a theoretically, & often practically, definable number. That degree is often closer on average (for a locale) than you might think.
In some cultures (East European Jewish, my own background, among them) it was the norm to marry your second or third cousins from a nearby town or village. Given that two of my great-grandparents on opposite sides of the family are from small towns a few miles from each other in what is now Ukraine, I imagine I’m probably related to myself on several levels. ;j
I also imagine this pattern explains the genetic predisposition of Ashkenazi Jews to certain hereditary (or at least partially hereditary) diseases: Tay-Sachs, breast cancer, etc.
OTOH an ex of mine, also of Ashkenazi origin from Ukraine (though much more recently - he was a first-generation immigrant) had two first cousins, sisters, whose parents were first cousins and married and had children before realizing they were first cousins. The large extended family was from the part of Ukraine that had been under Nazi occupation during WWII (and in fact, my ex’s father was a concentration camp survivor). During and after the war, his extended family had been scattered to the four winds, and many branches of the family (as was common during that time) had lost track of each other. Years after the wedding, while the children were small, his cousins’ parents were having a discussion about their childhoods and extended families, and realized just how closely they were related.
(While dabbling in Jewish genealogy over the past few years, I posted the small chunks of my family tree that I have documented so far online, and believe me, relatives started coming out of the woodwork. Even as recently as my mom’s childhood in NJ, there were something like 200 people from her extended family living in her hometown - there is no way I could name 200 relatives, total, so I imagine if I moved to parts of the NY/NJ area it wouldn’t be too difficult to run into a close relative without realizing it. Just a couple of generations ago, when family sizes were larger, just think: if your parents each had 5 siblings, each of whom had 6 kids, that’s a whole ton of first cousins - 60 on each side. And then if they each had 6 kids? Ouch.)
My family has two cousins who got married and their mothers were identical twins! They now have three normal boring children and live a very normal, boring life.