Math: Fleeting Thoughts

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Eebster the Great
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Re: Math: Fleeting Thoughts

Postby Eebster the Great » Mon Jan 14, 2019 4:35 pm UTC

doogly wrote:
gmalivuk wrote:One's son shouldn't be one's sibling...

The moral injunctions of Exodus can really go take a hike. 2019, brah.

Since this is the math forum, it's worth mentioning that the detrimental genetic effects from such a union are statistically significant but practically very small, in contrast to popular belief that they would typically be large. Also, a child of two first cousins is not significantly more likely to have genetic disorders than a random child.

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Re: Math: Fleeting Thoughts

Postby gmalivuk » Mon Jan 14, 2019 5:48 pm UTC

If someone's son is their brother, they reproduced with their mother or father. Which, in addition to having a much higher rate of defects, is also fucked up in loads of other ways that often wouldn't apply to (even double first) cousins.
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Re: Math: Fleeting Thoughts

Postby DavidSh » Mon Jan 14, 2019 5:49 pm UTC

If you are talking about half-siblings, or step-sons, you get the effects Eebster the Great was discussing. If you are genetic father of a genetic full-sibling, I think you have to be your own genetic father. That's not quite as extreme as the situation of the protagonist in All You Zombies, but still requires a causality violation. You might have genes that you inherited only from yourself, which haven't run through the process of human evolution. Who knows how well they will interact with human genes in any of your descendants? (The Time Patrol, that's who.)

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Re: Math: Fleeting Thoughts

Postby Eebster the Great » Mon Jan 14, 2019 6:00 pm UTC

gmalivuk wrote:If someone's son is their brother, they reproduced with their mother or father. Which, in addition to having a much higher rate of defects, is also fucked up in loads of other ways that often wouldn't apply to (even double first) cousins.

Yeah, the kid's parent is also his grandparent. It's fucked up, but the notion that the rate of genetic defects will be very high is simply incorrect. It will be higher than in the general population, but not by a lot. The examples of inbreeding we are used to seeing result from many generations of isolation, not just a single case of incest.

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Re: Math: Fleeting Thoughts

Postby gmalivuk » Mon Jan 14, 2019 6:09 pm UTC

Still, the coefficient of inbreeding for a son who's also a (half-)brother is four times higher than it is for the offspring of (non-double) first cousins, which is usually the point where some jurisdictions start allowing marriage. (Though I don't know how often those laws distinguish between double and non-double first cousins. That is, cousins who share one pair of grandparent, vs. those who share both.)
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Re: Math: Fleeting Thoughts

Postby Eebster the Great » Mon Jan 14, 2019 7:17 pm UTC

A majority of US states actually also prohibit first cousin marriage. North Carolina has the odd distinction of being the only state to allow single first cousin marriages but not double first cousin marriages. Sex is more broadly legal though.

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Re: Math: Fleeting Thoughts

Postby PM 2Ring » Tue Jan 15, 2019 7:19 am UTC

Wikipedia has lots of info on cousin marriage, including various maps. Also see cross cousin marriage from the University of Manitoba.

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Re: Math: Fleeting Thoughts

Postby gmalivuk » Tue Jan 15, 2019 3:31 pm UTC

All this info about marrying your cousin is interesting and all, but my initial point was that it would take several generations of cousin marriage to reach the level of inbreeding of a single parent-child pairing.
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Re: Math: Fleeting Thoughts

Postby Pfhorrest » Tue Jan 15, 2019 10:58 pm UTC

Flumble wrote:In any case, let's not discount any non-human entities that may work for degrees. They're worker-years.

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