Dec
23
2008

You know what else we do in the future? Cousins.

Prejudice against the rural poor: Well, sure, but a fictional rural poor. This gentleman is an urban musician who shops at trendy surplus stores, and it's too difficult to tell if his parents are closely related.
Prejudice against the rural poor: Well, sure, but a fictional rural poor. This gentleman is an urban musician who shops at trendy surplus stores, and it's too difficult to tell if his parents are closely related.Courtesy Poodleface
Well, Buzzketeers, we’re in the thick of the holiday season now—wading through that sticky caramel center of winter festivities, thigh-deep in a swamp of sweater clad relatives, up to our necks in mixed metaphors…

And, you know what? I hope you dig it. That’s my gift to y’all: the honest wish that you are all enjoying your elbow to elbow time with your closest kin. There’s your non-denominational seasonal gift, everyone, I hope you like it. (Personally I celebrate “Wintermania,” during which my family falls into a Wham!-induced frenzy, and then sacrifices anything to our winter deities. We come out of it with a lot fewer pets and household appliances, but it’s an exciting and high-spirited occasion. But I won’t force my beliefs on you.)

There’s some extra thought behind my gift, though. I mean, I know you’ll like it anyway, but it’s practical too! See, it just might happen that, someday, you’ll be bumping more than elbows with your cousins, and working your way up to that may start with the holiday conviviality. So you’re welcome for my making your life easier.

“What?” you say. “I’m not doing… that… with my cousin!”

Nor should you, sensitive Buzzketeer, nor should you. Necessarily.

But you could. Generally not legally, of course. But it turns out that, genetically, the whole “kissin’ cousins” thing might not be as problematic as you have been lead to believe. So says a new article on population genetics in the journal PLoS Biology.

See, the thing about serious inbreeding with close relatives is that it drains your gene pool—it reduces the variety of genes in your offspring. There are a couple reasons to have a nice assortment of genetic traits in a population. If everyone is the same genetically, then they all have the same genetic vulnerabilities, and something like a specialized disease or an abrupt change in the environment could wipe out the whole group. Also, and here’s the kissin’ cousins problem, a lot of genetic disorders result from having two recessive genes matched up in your DNA. If you just have one recessive gene for a disorder, you won’t develop the disorder, but you could pass that gene on to your kid, and if the kid got another copy of that recessive gene from his or her other parent, the kid would develop the disorder. People get disorders caused by matched recessive genes even when their parents aren’t related at all, but if a recessive gene for a particular disorder runs in a family, the chances that a kid in that family will get the gene from both parents is greatly increased if those parents are related.

That’s the idea, anyway. The folks who published this new article, however, say that, in reality, the chances that the offspring of two cousins will have birth defects (caused by recessive genes pairing up) really isn’t as great as most of us think. Specifically, the odds that two cousins would produce a child with congenital defects are only 1-2% greater than those for the rest of the un-related, child-producing population. Women over 40 have a similar risk of having children with congenital defects, the researchers point out, and there are no laws prohibiting them from having kids, whereas 31 states have laws against cousins being married. Laws like these, they say, aren’t based in solid science and reflect “outmoded prejudices about immigrants and the rural poor.”

So there. Do with your present what you will. Try it on for size, or give it to someone else—you won’t hurt my feelings. Merry Wintermania!

Your Comments, Thoughts, Questions, Ideas

Anonymous's picture
Anonymous says:

ok. well, isn't the chances only extremely higher if the pattern of marrying cousins continues for many generations within the same families. that's what i've always thought.

posted on Tue, 12/23/2008 - 9:46pm
JGordon's picture
JGordon says:

Yeah, I think you have the right idea; the more ancestors a couple of people share, the more likely the chance they'll pass on a homozygous recessive pair of genes to their offspring.

Having matched recessive genes isn't necessarily always a bad thing. Blue eyes, for instance, are the result of a pair of recessive genes, and there's nothing wrong with having blue eyes. But if members of a family are carriers of a genetic condition (meaning that they have one copy the recessive gene) like hemophilia, then passing on a matched set of genes to a child could lead to serious health problems.

posted on Mon, 12/29/2008 - 11:04am

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