Anonymous asked:
sigmaleph answered:
cousin marriage is icky
doesn’t make it wrong, but
I’ve been reading about leptin receptor deficiency recently, which is mostly (only?) observed in children of cousin marriages. Stephen Guyenet describes affected children as follows:
Usually they are of normal birth weight and then they’re very, very hungry from the first weeks and months of life. By age one, they have obesity. By age two, they weigh 55-65 pounds, and their obesity only accelerates from there. While a normal child may be about 25% fat, and a typical child with obesity may be 40% fat, leptin-deficient children are up to 60% fat. Farooqi explains that the primary reason letpin-deficient children develop obesity is that they have “an incredible drive to eat”…leptin-deficient children are nearly always hungry, and they almost always want to eat, even shortly after meals. Their appetite is so exaggerated that it’s almost impossible to put them on a diet: if their food is restricted, they find some way to eat, including retrieving stale morsels from the trash can and gnawing on fish sticks directly from the freezer. This is the desperation of starvation […]
Unlike normal teenagers, those with leptin deficiency don’t have much interest in films, dating, or other teenage pursuits. They want to talk about food, about recipes. “Everything they do, think about, talk about, has to do with food” says Farooqi. This shows that the [leptin system] does much more than simply regulate appetite - it’s so deeply rooted in the brain that it has the ability to hijack a broad swath of brain functions, including emotions and cognition.
Marrying your cousin is like winning access to a whole new, much more interesting tier of genetic diseases.
But one, HOW MUCH does it increase the risk of those diseases and two, no one said they had to reproduce (okay, so it’s usually implied, but)
There are certain rare diseases (and I think leptin receptor deficiency is one) that are pretty limited to cousin marriage, but the overall risk is still low (vanishingly low for any given one, a few percent for all put together). In terms of risk of genetic disease as a whole, I think it increases it by about 50% - 100%, from 4%ish to 7%ish.
But this can seriously compound over time. See eg http://blogs.discovermagazine.com/gnxp/2010/08/the-individual-social-risks-of-cousin-marriage/