# Brother from Another Mother



## Androxine Vortex (Jun 20, 2012)

Yo!

Ok, enough of that!

My MC in a novel I am working on lives in a very primitive tribe (culturaly based off of the native American Indians) They are very loyal to their clan family and never mate anyone from another tribe or leave their tribe. There are roughly about thirty people in the clan.

But this is the issue: At some point they would have to start mating with people that they would be related to. Thirty is a pretty small number too. I haven't a clue about this stuff but I do know that it can lead to genetic problems. I really don't know what I should do about this. I want to emphasize the fact that they are very close and tribalistic but I don't want my characters to have genetic problems. And again thrity is kind of small. Would there be any genetic problems? I just don't know anything about this stuff. Thanks a lot if you can help!

EDIT: Yes I suppose I could have them just find partners from outside their tribe but if i can have it this way I would prefer it, thanks


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## Steerpike (Jun 20, 2012)

There wouldn't have to be genetic problems. If you have a small population like that, then genetic abnormalities can easily become fixed in a population, if they exist. Also, to the extent that members of the population are carrying a detrimental genetic trait (for example one that is recessive), mating with related individuals increases the likelihood that the child will have the genetic disorder. But the bad gene has to be there to begin with. That's an oversimplification, but the upshot is that there is no reason a small population that interbreeds HAS to have genetic abnormalities.

Since it is a common assumption that they would, however, it might be worth addressing why they do not.


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## Androxine Vortex (Jun 20, 2012)

Steerpike said:


> There wouldn't have to be genetic problems. If you have a small population like that, then genetic abnormalities can easily become fixed in a population, if they exist. Also, to the extent that members of the population are carrying a detrimental genetic trait (for example one that is recessive), mating with related individuals increases the likelihood that the child will have the genetic disorder. But the bad gene has to be there to begin with. That's an oversimplification, but the upshot is that there is no reason a small population that interbreeds HAS to have genetic abnormalities.
> 
> Since it is a common assumption that they would, however, it might be worth addressing why they do not.



Ok good. I didn't really know anything about inbreeding so I wasn't sure. And who says the bad gene has to be something horrendous?  Maybe one tribe's defect is that all of their eyes are yellow or something like that.


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## Steerpike (Jun 20, 2012)

Or it could be an advantageous gene. Same principle. Good genes also get fixed in the population.


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## Androxine Vortex (Jun 20, 2012)

Steerpike said:


> Or it could be an advantageous gene. Same principle. Good genes also get fixed in the population.



True I read somewhere though that inbreeding can cause a greater probability of harmful genes and the closer the relation to the partners the greater the chances and severity. But I suppose beneficial genes can be factored in there as well.


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## topazfire (Jun 28, 2012)

I think thirty might be too small for a tribe actually. My immediate paternal family has over 30 people becuase my dad is one of 5 brothers (plus each with a wife and at least two kids = 30+ at our family bbq's)

I would consider a small family tribe to number at least 60, and to make sure that you can identify each generation. In such a small group it would be very important to know exactly how you are related to each other. My great aunt and great uncle (from the same small town) both moved to the big city, got married to each other, and only after, found out that they were first cousins. And yes, there are some issues that can happen with offspring of two people who are that closely relate. 

My advise would be to make sure you have a very detailed family tree, and make sure the numbers work for your story but are still realistic to readers who may come from large families and view the intermarrying situation as odd or even possibly disturbing. 

I would love to hear more!


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## Androxine Vortex (Jun 28, 2012)

topazfire said:


> I think thirty might be too small for a tribe actually. My immediate paternal family has over 30 people becuase my dad is one of 5 brothers (plus each with a wife and at least two kids = 30+ at our family bbq's)
> 
> I would consider a small family tribe to number at least 60, and to make sure that you can identify each generation. In such a small group it would be very important to know exactly how you are related to each other. My great aunt and great uncle (from the same small town) both moved to the big city, got married to each other, and only after, found out that they were first cousins. And yes, there are some issues that can happen with offspring of two people who are that closely relate.
> 
> ...



Well what if they followed strict rules for marrying/mating? If they kept to a standard proceedure I suppose but this is very hard to sort out in my head!


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## Caged Maiden (Jun 28, 2012)

Tribal people often swapped members to avoid just the thing you are trying to work through.  Women would join a new tribe and become a valued member of their new families.

Imagine being raised up knowing you are destined to marry your uncle who is 20 years older than you, or that when you are changing your niece's diaper, she's already slated to be your wife.

The real problem I see is that there will be generation gaps and within a few generations, everyone will be related.  Where did the current 30 individuals come from?  are they escapees from a crushed village and they band together and decide to marry their offspring to each other, or are they already related?  If these people have already been inbreeding, they are likely already showing effects, infertility being one.

Now when selectively breeding, you can combine a parent and their child better than a brother and sister.  I'd look into cattle breeding if you want to check feasibility.

The thing with cattle is that they aren't selecting mates with emotional and moral questions on their minds.  Humans are a little different.  Probably the best thing you could do for your culture is make one woman have children with three or four different men, to keep most of the people only half-related rather than having three or four or more children from having the exact two parents.

I don't know if you know a lot about history, but people sort of knew marrying your brother was a bad idea.  Look at the history of the English monarchy.  There was a reason so many royal children were sickly, they were all inbred.


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## Jess A (Jul 3, 2012)

Thirty is genetically way too small in my opinion. It would not be viable for many generations.

Maybe there is a ritual where a mating occurs between their tribe and another? A strict sort of 'swap' to introduce new genes into the genepool. Women could mate with a male from another tribe in a ritualistic manner, but the women may be married to a man from their own tribe - and together they raise the resulting children. Most males prefer to spread their own genes but humans aren't quite lions.

As Caged Maiden said - where did these people come from? Did they begin as thirty unrelated individuals or are they already all related (or made up of, for example, four or five or six family clans)? If they are an established clan then I'm betting they are already all related in some way. For a bit of fun and clarity, draw out a family tree/map of the clan families.


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## Ireth (Jul 3, 2012)

Caged Maiden said:


> Imagine being raised up knowing you are destined to marry your uncle who is 20 years older than you, or that when you are changing your niece's diaper, she's already slated to be your wife.



*shudders* That makes me think of the imprinting thing with the wolves in Twilight.


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## Saigonnus (Jul 4, 2012)

I think along the same lines as most others in that thirty is much too small of a clan to have a viable gene pool... even the smallest of the native american or island cultures had to find ways to suppliment their limited numbers to avoid inbreeding. Mostly it was the perpetual wars that actually kept most of the clans genetically clean, for their perpensity for taking captives of women from raids; who would become wives or at least breeding vessels to tribesmen.

I think 120 people at the minimum (more if they are warlike) would be sufficient to keeping the gene pool relatively clean even without the introduction of new blood into the gene pool. The breeding though would have to be strictly managed and perhaps that is a concept they wouldn't even be capable of contemplating. 

I have a concept for a story (haven't done much with it really) that is similar to yours in many ways. Basically a small group of mainlanders from the continent get stranded on a large island that is already inhabited by tribes of "primitives". Most of these tribes are at war with others but since most are fairly small, they have no choice but to find new blood where they can. Twice a year, whether they are at war with a tribe or not; it has become tradition to have gatherings in which any tribe can send their unmarried/available boys and girls to search for a mate among the gathering.

It has become almost a political force in that the leaders of the other clans (not the ones the couple belong to) will negotiate which tribe gets the newly "married couple" the boy's tribe, or the girl's so each tribe (the boys' or girls') will offer gifts or trade rights to those clans deciding will have the new couple go with them.


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## Twilight Goblin (Jul 11, 2012)

Steerpike said:


> There wouldn't have to be genetic problems. If you have a small population like that, then genetic abnormalities can easily become fixed in a population, if they exist. Also, to the extent that members of the population are carrying a detrimental genetic trait (for example one that is recessive), mating with related individuals increases the likelihood that the child will have the genetic disorder. But the bad gene has to be there to begin with. That's an oversimplification, but the upshot is that there is no reason a small population that interbreeds HAS to have genetic abnormalities.
> 
> Since it is a common assumption that they would, however, it might be worth addressing why they do not.




Since it is a tribe with thirty-odd people, it could repopulate with each other for an estimated time of about eight generations. Of course, you could have the women be like Amazons and go out to find some man to have intercourse with, then come back to the tribe to birth and raise the child.


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## Ireth (Jul 11, 2012)

Twilight Goblin said:


> Since it is a tribe with thirty-odd people, it could repopulate with each other for an estimated time of about eight generations. Of course, you could have the women be like Amazons and go out to find some man to have intercourse with, then come back to the tribe to birth and raise the child.



Also there's an opposite issue to think about. If the tribe were ever attacked by a band of pillaging and plundering bandits, there might easily be illegitimate offspring to care for as a result of women being raped. That would vary the gene pool further.


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