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Friends are as genetically similar as fourth cousins

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Re: Friends are as genetically similar as fourth cousins

#102

Earlier quoted context omitted.

Arbitrary? You have the same parents with sibling; with cousin you share only one of the two pairs of grandparents.

Actually that's often but not always true - brother b1 and sister s1 from family 1, with parents g1 brother b2 and sister s2 from family 2, with parents g2 s1 has child x with b2 - x has grandparents g1, g2 s2 has child y with b1 - y has grandparents g1, g2 x and y are cousins, and also share the same 2 pairs of grandparents :-)

It can get even more fun!

If instead of two brothers marrying two sisters, you have two brothers marrying two first cousins, like so...

    b1 and b2 are brothers
    c1 and c2 are first cousins
    b1 and c1 marry and have child x
    b2 and c2 marry and have child y
... then x and y are both first and second cousins (and their children are second + third cousins, etc).

Re: Friends are as genetically similar as fourth cousins

#103
post #15
post #3

In case you were also wondering what a "fourth cousin" was, someone who shares a pair of great-great-great grandparents[0]. Wikipedia has a great set of diagrams[1] in case you're also confused about first, second, or third cousins. I figure through induction you can presume any nth and nth removed from that page (I foolishly thought 3rd was where people arbitrarily stopped keeping count....) [0] https://www.referenc…

I get mad at people who think sons of first-cousins are second-cousins all the time -- and, frankly, almost everyone I know think this way. I'm glad you linked to this Wikipedia article that proves I'm not mad into thinking there is a simple logic pattern that can be applied to cousinship. However, this "once removed" notation is crazy. Why not second-uncle for parents of second-cousins and so on?

That's how we've always done it.

* Brother of father is uncle. Son of uncle is cousin. Son of son of uncle is second cousin.

* Brother of grandfather is great-uncle. Son of great-uncle is second cousin.

Re: Friends are as genetically similar as fourth cousins

#104

The lead author, Nicholas Christakis, is the man who was reviled by some students at Yale during the Halloween costume debacle: http://www.theatlantic.com/politics/archive/2015/11/the-new-... .

I hope you're not suggesting that has any bearing on the quality of the paper?

Re: Friends are as genetically similar as fourth cousins

#105

The lead author, Nicholas Christakis, is the man who was reviled by some students at Yale during the Halloween costume debacle: http://www.theatlantic.com/politics/archive/2015/11/the-new-... .

Thanks for reposting that article. I swear I'm starting to feel like an old man "back in my day, vigorous intellectual disagreement and debate was the point of living on campus during college"

Re: Friends are as genetically similar as fourth cousins

#106

The lead author, Nicholas Christakis, is the man who was reviled by some students at Yale during the Halloween costume debacle: http://www.theatlantic.com/politics/archive/2015/11/the-new-... .

I hope you're not suggesting that has any bearing on the quality of the paper?

I don't think there's any implication of that. It's just a nice piece of trivia.

Re: Friends are as genetically similar as fourth cousins

#107
post #15

Earlier quoted context omitted.

I get mad at people who think sons of first-cousins are second-cousins all the time -- and, frankly, almost everyone I know think this way. I'm glad you linked to this Wikipedia article that proves I'm not mad into thinking there is a simple logic pattern that can be applied to cousinship. However, this "once removed" notation is crazy. Why not second-uncle for parents of second-cousins and so on?

Pardon me for my ignorance, but wouldn't sons of first cousins be second cousins?

He must be referring to one's own first cousin's children. Not the children of two first cousins.

Re: Friends are as genetically similar as fourth cousins

#109
post #3

In case you were also wondering what a "fourth cousin" was, someone who shares a pair of great-great-great grandparents[0]. Wikipedia has a great set of diagrams[1] in case you're also confused about first, second, or third cousins. I figure through induction you can presume any nth and nth removed from that page (I foolishly thought 3rd was where people arbitrarily stopped keeping count....) [0] https://www.referenc…

It is mentioned in some comments of comments further down but Wolfram Alpha has some great family tree generation.

http://www.wolframalpha.com/input/?i=fourth+cousin

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