# A mathematical question about inbreeding **URL:** \ **Category:** Factual Questions\ **Created:** [June 16, 2009, 6:39pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971 "2009-06-16T18:39:14Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Sampiro](https://avatars.discourse-cdn.com/v4/letter/s/2acd7d/32.png) [@Sampiro](https://boards.straightdope.com/u/Sampiro)\ **Post date:** [June 16, 2009, 6:39pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/1 "2009-06-16T18:39:14Z")
Hypothetical question (though I’m sure there’s an inbred part Eskimo Little Susie somewhere): Little Susie’s parents are happily married first cousins. (For the purposes of this I could make them brother and sister but even for hypothetical that’s a bit icky, so I’ll stick to first cousins.) So, Little Susie’s parents are first cousins, meaning they share one set of grandparents. Let’s further suppose that one of their shared grandparents is an Eskimo. This means that Little Susie has two parents and four grandparents. However, because her parents are first cousins there are only six individuals who are her great-grandparents. Does this mean that Little Susie is 1/6 Eskimo (since one of her six great-grandparents is an Eskimo) or that she is 1/4 (2/8) Eskimo (since each of her parents has one Eskimo grandparent, who happens to be the same person, and each of her parents is 1/4 Eskimo)? Now let’s assume that one of Susie’s parents had a grandmother who was Lithuanian, and it was NOT one of the shared grandparents the cousin/spouses had. This makes her parent 1/4 Lithuanian. So is Little Susie 1/8 Lithuanian (because she’s 1/2 of a 1/4 Lithuanian parent) or does it make her 1/6 Lithuanian (since of the 6 individuals who were her great-grandparents, 1 was Lithuanian)? ---
**Author:** ![JonathanTheRed](https://avatars.discourse-cdn.com/v4/letter/j/8491ac/32.png) [@JonathanTheRed](https://boards.straightdope.com/u/JonathanTheRed)\ **Post date:** [June 16, 2009, 6:58pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/2 "2009-06-16T18:58:27Z")
Susie is 100% human. Categories like “Eskimo” and “Lithuanian” are vague enough that the genetic implications are unclear. But that’s a dodge. Susie is 1/4 Eskimo and 1/8 Lithuanian, as you suspect. More precisely: she gets 100% of her genes from her parents. She gets 50% of her genes from her maternal grandparents, 50% from her paternal grandparents. And she gets 25% of her genes from one of her sets of great-grandparents, 25% from another set, and 50% from the great-grandparents shared as grandparents to her parents. Half of those genes come from her Eskimo double-great-grandparent, so she shares 25% of her genes with him. ---
**Author:** ![ITR\_champion](https://avatars.discourse-cdn.com/v4/letter/i/c67d28/32.png) [@ITR\_champion](https://boards.straightdope.com/u/ITR_champion)\ **Post date:** [June 16, 2009, 7:01pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/3 "2009-06-16T19:01:02Z")
In terms of genetic material, 25% (one quarter) of Susie’s came from Eskimos and 12.5% (one eighth) came from Lithuanians. Whether that’s the legal answer, I’m not sure and the answer may be different in different countries. ---
**Author:** ![Sampiro](https://avatars.discourse-cdn.com/v4/letter/s/2acd7d/32.png) [@Sampiro](https://boards.straightdope.com/u/Sampiro)\ **Post date:** [June 16, 2009, 7:02pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/4 "2009-06-16T19:02:58Z")
> [@JonathanTheRed](#): > > Susie is 100% human. Categories like “Eskimo” and “Lithuanian” are vague enough that the genetic implications are unclear. Then I’ll rephrase. Susie’s parents have one grandfather who is from [Orion](http://www.thehollywoodgossip.com/images/gallery/all-green.jpg). Her mother, but not her father, is also 1/4 vampire. Now that the human element is gone… how non human is Susie? ---
**Author:** ![JonathanTheRed](https://avatars.discourse-cdn.com/v4/letter/j/8491ac/32.png) [@JonathanTheRed](https://boards.straightdope.com/u/JonathanTheRed)\ **Post date:** [June 16, 2009, 7:08pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/5 "2009-06-16T19:08:59Z")
> [@Sampiro](#): > > Then I’ll rephrase. Susie’s parents have one grandfather who is from [Orion](http://www.thehollywoodgossip.com/images/gallery/all-green.jpg). Her mother, but not her father, is also 1/4 vampire. > > Now that the human element is gone… how non human is Susie? Well, she’s got 25% Orionese blood, which I think we can all agree are non-human. The vampire question is tougher, since the humanity or lack thereof of the undead is open to debate. As far as I know, most vampires were once ordinary people, and does vampirification alter the DNA, including the DNA in the sex cells? I’ve only seen a couple of peer-reviewed articles on the subject, and their results were inconclusive. As an aside: if vampires remain fertile, that implies that premenopausal female vampires menstruate. The implications of this are left as an exercise for the sick mind. ---
**Author:** ![Sampiro](https://avatars.discourse-cdn.com/v4/letter/s/2acd7d/32.png) [@Sampiro](https://boards.straightdope.com/u/Sampiro)\ **Post date:** [June 16, 2009, 7:12pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/6 "2009-06-16T19:12:55Z")
> [@JonathanTheRed](#): > > Well, she’s got 25% Orionese blood, which I think we can all agree are non-human. The vampire question is tougher, since the humanity or lack thereof of the undead is open to debate. As far as I know, most vampires were once ordinary people, and does vampirification alter the DNA, including the DNA in the sex cells? I’ve only seen a couple of peer-reviewed articles on the subject, and their results were inconclusive. > > As an aside: if vampires remain fertile, that implies that premenopausal female vampires menstruate. The implications of this are left as an exercise for the sick mind. In Little Susie’s case it becomes extra difficult as the Vampire great grandfather has recently become a born again Baptist and is participating in their RESURRECTION program which they claim makes vampires human again. (It meets in the same places as EXODUS and there’s been bloodshed and hook ups galore, but it’s been covered up.) AND The vampire has a grandmother who was a weredolphin. ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [June 16, 2009, 7:31pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/7 "2009-06-16T19:31:51Z")
> [@Sampiro](#): > > In Little Susie’s case it becomes extra difficult as the Vampire great grandfather has recently become a born again Baptist and is participating in their RESURRECTION program which they claim makes vampires human again. (It meets in the same places as EXODUS and there’s been bloodshed and hook ups galore, but it’s been covered up.) AND The vampire has a grandmother who was a weredolphin. I don’t think the weredolphin screws up the genetics. Now if she was, say, a were-aphid (aphids can reproduce parthenogetically or sexually, depending on situation), the genetics could get interesting… ---
**Author:** ![JonathanTheRed](https://avatars.discourse-cdn.com/v4/letter/j/8491ac/32.png) [@JonathanTheRed](https://boards.straightdope.com/u/JonathanTheRed)\ **Post date:** [June 16, 2009, 8:03pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/8 "2009-06-16T20:03:50Z")
> [@Sampiro](#): > > In Little Susie’s case it becomes extra difficult as the Vampire great grandfather has recently become a born again Baptist and is participating in their RESURRECTION program which they claim makes vampires human again. Oh, for the love of Pete. What is this, Lysenkoism? You can cut off a rat’s tail and its offspring will still have tail-lengths dictated by the parent’s genes, not outward characteristics. The Baptists can do whatever they want to Susie’s great-zayde, and it won’t change the nucleic acid packed into his sperm. Judging from its symptoms, onset, and mode of transmission, vampirism is a disease brought about by an external agent, not a genetic abnormality. (At worst, genotype might make an organism more _susceptible_ to vampirism.) So calling Susie “1/8 vampire” makes as much sense as saying that Ichiro Suzuki’s grandchildren are 1/4 Seattle Mariner. > [@](#): > > (It meets in the same places as EXODUS and there’s been bloodshed and hook ups galore, but it’s been covered up.) AND The vampire has a grandmother who was a weredolphin. Well now I’m starting to suspect that you’re just making this up. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [June 16, 2009, 8:27pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/9 "2009-06-16T20:27:28Z")
I don’t know what the hell is going on here, but I’d like to volunteer to head up the research program. ---
**Author:** ![Sampiro](https://avatars.discourse-cdn.com/v4/letter/s/2acd7d/32.png) [@Sampiro](https://boards.straightdope.com/u/Sampiro)\ **Post date:** [June 16, 2009, 9:10pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/10 "2009-06-16T21:10:38Z")
> [@JonathanTheRed](#): > > Judging from its symptoms, onset, and mode of transmission, vampirism is a disease brought about by an external agent, not a genetic abnormality. (At worst, genotype might make an organism more _susceptible_ to vampirism.) So you’re saying “It’s just a lifestyle choice” then? You fangophobes make me sick. 😉 ---
**Author:** ![JonathanTheRed](https://avatars.discourse-cdn.com/v4/letter/j/8491ac/32.png) [@JonathanTheRed](https://boards.straightdope.com/u/JonathanTheRed)\ **Post date:** [June 16, 2009, 9:15pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/11 "2009-06-16T21:15:22Z")
> [@Sampiro](#): > > So you’re saying “It’s just a lifestyle choice” then? You fangophobes make me sick. You’re the one meticulously trying to figure out Susie’s exact percentage of vampire blood. Why, if it’s too high you’ll make her ride at the back of the bus? ---
**Author:** ![Sampiro](https://avatars.discourse-cdn.com/v4/letter/s/2acd7d/32.png) [@Sampiro](https://boards.straightdope.com/u/Sampiro)\ **Post date:** [June 16, 2009, 9:27pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/12 "2009-06-16T21:27:10Z")
> [@JonathanTheRed](#): > > You’re the one meticulously trying to figure out Susie’s exact percentage of vampire blood. Why, if it’s too high you’ll make her ride at the back of the bus? No, but in a coffin on a dog sled maybe. Actually I’m doing genealogy and trying to figure out how to figure descent from direct ancestors who appear in more than one place on the family tree. (My own family tree could just about be drawn on a Möbius strip due to an odd series of intermarriages, but like most people who’ve had ancestors in the US for centuries there are some cousin marriages in there as well.) ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [June 16, 2009, 10:05pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/13 "2009-06-16T22:05:22Z")
> [@JonathanTheRed](#): > > Judging from its symptoms, onset, and mode of transmission, vampirism is a disease brought about by an external agent, not a genetic abnormality. But not everybody is 100% vampiric or not; surely some people are bi-vampiric, to varying degrees. And I, for one, find the term “disease” to be offensive. Remember, this is GQ. ---
**Author:** ![missred](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/missred/32/14096_2.png) [@missred](https://boards.straightdope.com/u/missred)\ **Post date:** [June 16, 2009, 11:05pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/14 "2009-06-16T23:05:59Z")
To use the original ethnicticities: Susie would be 1/4 Eskimo and 1/4 other from one parent and 1/4 Eskimo and 1/4 Lithuanian from the other. Total of 1/2 Eskimo, 1/4 Lithuanian and 1/4 other. Common ancestors count on both sides seperately. I’ve run into a few of these in my family as well. ---
**Author:** ![JonathanTheRed](https://avatars.discourse-cdn.com/v4/letter/j/8491ac/32.png) [@JonathanTheRed](https://boards.straightdope.com/u/JonathanTheRed)\ **Post date:** [June 16, 2009, 11:54pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/15 "2009-06-16T23:54:12Z")
> [@missred](#): > > To use the original ethnicticities: > > Susie would be 1/4 Eskimo and 1/4 other from one parent and 1/4 Eskimo and 1/4 Lithuanian from the other. Total of 1/2 Eskimo, 1/4 Lithuanian and 1/4 other. Sorry, Miss Red, this is wrong. Susie’s parents were _first cousins_, not siblings. This means that Susie’s parents do not share parents, and all four of Susie’s grandparents are unique. It’s Susie’s \*great-\*grandparents in which there is overlap. Susie has six distinct people for great-grandparents, two of which appear twice at that level in her family tree. We’re given that one of those two is Eskimo, and another great-grandparent is Lithuanian. Of the eight “slots” of Susie’s ancestry three generations ago, two are filled with Eskimos (but only one person, appearing twice) and one by a Lithuanian. Susie’s 1/4 Eskimo, not 1/2, and 1/8 Lithuanian, not 1/4. (edit: I completely misread where you went wrong. If one of your parents is half Klingon and your other parent is half Klingon, you’re half Klingon, not full.) Sampiro, I hope this thread has answered your question and helps you in your genealogical research. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 17, 2009, 12:18am UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/16 "2009-06-17T00:18:34Z")
> [@](#): > > (edit: I completely misread where you went wrong. If one of your parents is half Klingon and your other parent is half Klingon, you’re half Klingon, not full.) [chief grukgruk half-orc, too. other half, also orc.](http://www.giantitp.com/comics/oots0555.html) ---
**Author:** ![missred](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/missred/32/14096_2.png) [@missred](https://boards.straightdope.com/u/missred)\ **Post date:** [June 17, 2009, 11:04pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/17 "2009-06-17T23:04:41Z")
> [@missred](#): > > To use the original ethnicticities: > > Susie would be 1/4 Eskimo and 1/4 other from one parent and 1/4 Eskimo and 1/4 Lithuanian from the other. Total of 1/2 Eskimo, 1/4 Lithuanian and 1/4 other. > > Common ancestors count on both sides seperately. I’ve run into a few of these in my family as well. Oops! Read the next post. ---
**Author:** ![missred](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/missred/32/14096_2.png) [@missred](https://boards.straightdope.com/u/missred)\ **Post date:** [June 17, 2009, 11:29pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/18 "2009-06-17T23:29:56Z")
Sheesh…and I still didn’t get it right :smack:. I meant 1/4 Eskimo. :smack::smack::smack: ---
**Author:** ![goodie](https://avatars.discourse-cdn.com/v4/letter/g/839c29/32.png) [@goodie](https://boards.straightdope.com/u/goodie)\ **Post date:** [June 19, 2009, 12:53pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/19 "2009-06-19T12:53:05Z")
My vampire granny used to make the BEST blood pudding at Thanksgiving. 😉 ---
**Author:** ![AskNott](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asknott/32/5790_2.png) [@AskNott](https://boards.straightdope.com/u/AskNott)\ **Post date:** [June 19, 2009, 2:32pm UTC](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971/20 "2009-06-19T14:32:38Z")
> [@goodie](#): > > My vampire granny used to make the BEST blood pudding at Thanksgiving. 😉 Served with the 1/4 Eskimo Pie? [Next page](https://boards.straightdope.com/t/a-mathematical-question-about-inbreeding/499971.md?page=2)