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I'm one-third confused

Okay, tell me if my instincts are right here.

In a novel I'm reading, a character mentioned being "one-third French" and two-thirds something else. My instinct is that you can't actually be one-third, or two-thirds, anything. Doesn't your genealogy have to come in halves and quarters and eighths and so on? You have two parents, four grandparents, eight great-grandparents, etc. So is it actually possible to be "one-third" any given ethnic group?

Math people, enlighten us.

If my instincts are right, please add "I'm one-third [blank]" to the official list of fallacious things your characters should never say.

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( 19 comments — Leave a comment )
mariole
Nov. 17th, 2008 05:16 am (UTC)
> Doesn't your genealogy have to come in halves and quarters and eighths and so on?

Yeah. It's that 2-parent thing. Gilgamesh was 2/3 a diety, but it was silly back then and it's silly now.
mollyringle
Nov. 18th, 2008 12:04 am (UTC)
Hehe. Well, this novel does have paranormal aspects, but I don't think they're going quite that far.
mongo
Nov. 17th, 2008 05:58 am (UTC)
Well if you want to go poetic (and abandon the math all together).

If you had a step-parent for whatever reason, you could have 3 parents and while it would have no effect on your genetic background, it would definitely affect your cultural one.

It's a reach at best, or pretentious so it should probably go on the list anyway.
mollyringle
Nov. 18th, 2008 12:04 am (UTC)
Hm, that's true. It depends how you define your heritage, I suppose.
sea0tter12
Nov. 17th, 2008 06:07 am (UTC)
Well, I suppose if you want to get technical, there is probably some multiple of grandparents and great-grandparents, where, if you divided by three, the numbers would work. Therefore, there is probably a way to be one-third something, just not likely ;)
sea0tter12
Nov. 17th, 2008 06:08 am (UTC)
Or, if you figure in that some of the grandparents are 1/2 whatever or 1/4 whatever, there is probably a way to do it. I'm just too tired to think too hard about it :)
mollyringle
Nov. 18th, 2008 12:06 am (UTC)
As far as I can tell, it's possible to get a number very close to 33.3333%, but probably never exactly one-third, because the fractions' denominators always have to be logs of two. (2, 4, 8, 16, 32, 64, etc.) And I don't think those ever hit anything divisible by 3. But then, a list that goes to infinity could include a lot that escapes me right now. :)
second_banana
Nov. 17th, 2008 06:23 am (UTC)
I'm with seaOtter12. It's probably possible, but I'd certainly add it the list of things your characters should never say because it takes your readers waaaaay out of the story. And anything that does that is bad news bears.
mollyringle
Nov. 18th, 2008 12:07 am (UTC)
*nod* If we get a writing lesson out of it, at least, then it was worth the effort of thinking it over.
ekatarina
Nov. 17th, 2008 06:52 am (UTC)
Lineage deals only with logs of 2. So with far enough back and some rounding it would work, but, really, for all intents and purposes, no, it doesn't make sense.

Ekatarina
mollyringle
Nov. 18th, 2008 12:08 am (UTC)
That's what I came to as well. Only works if you round it a bit. But I can see how people would, since saying "21 64ths" is a bit silly. :)
shmuel
Nov. 17th, 2008 11:43 am (UTC)
I think if three out of eight great-grandparents were French (37.5%), saying "one-third" (33.3%) would be the most natural usage. (Five great-great-grandparents would be even closer, at 31.25% -- would anybody really bother saying "five-sixteenths" instead of "one-third"? -- but it's not necessary to stretch that far back.)
mollyringle
Nov. 18th, 2008 12:08 am (UTC)
I concluded that as well. Works if you round it, and it makes sense that people would. But, as a math question, it's probably never exactly one-third.
(Deleted comment)
mollyringle
Nov. 18th, 2008 12:09 am (UTC)
And didn't the Conehead aliens on SNL (from way back) claim they were "from France"? :)
(Anonymous)
Nov. 17th, 2008 11:00 pm (UTC)
Easy answer
If the character's parents are half-siblings, the character only has three grandparents. That's a bit gross, perhaps, but the principle behind it--people appearing more than once in the family tree--is common enough, and can lead to any fraction you like.
mollyringle
Nov. 18th, 2008 12:11 am (UTC)
Re: Easy answer
Hee. Yeah, my little sister and her husband proposed that too, which I hadn't thought of. But even then, does it really work?

Sure, if your one grandpa is French and your two grandmas are Spanish, you could say you're one-third French and two-thirds Spanish.

But in that scenario, both your parents would be half French, half Spanish. So wouldn't that also mean you were, too?

I can't decide.
(Anonymous)
Nov. 18th, 2008 07:30 am (UTC)
Re: Easy answer
You're right, that doesn't work--it's just a variation on the Monty Hall problem. Grandpa should be counted twice--he is functionally two grandpas, not one.
(Anonymous)
Jan. 5th, 2009 09:42 pm (UTC)
What if one grandparent was French, one was half French half something else, and the other two were something else?
So then you have one parent 3/4 French.
Which makes the character 3/8 French, like someone else suggested. Close enough, I guess.
( 19 comments — Leave a comment )