Expository conversation from random genetic-bottleneck-based dystopia setting idea

[A conversation at Ana Mardoll's got me thinking about this.]
[Italics person has broken into a secret library and is trying to find out the truth of the society's history.  Non-italics person comes out and starts correcting her, then the scene starts]

Who are you?

I'm the record keeper, the archivist, the librarian.  Take your pick.  Back before history was deemed heretical we were a respectable group who existed to help anyone and everyone learn about the past, do our best to record the present, and work to make sure those in the future would remember.

We didn't used to to be hereditary, we didn't used to be underground--

We?

Well, when I talk about the group I say "we".  I'm the only one left, but I'm part of a group that stretches back to the beginning.  Not that you'd know about that.  I doubt you even know that there was a beginning.

Everything has a beginning.  Besides, there's no way things could have always been as wrong as they are now.

Smart one.  What else do you know?  Do you know why we call everyone who hasn't been outcast Dellidies?

Uh, it's the name of our people.  What else would we call them?

Well, originally, we were called "Aridellidies".  It means "the children of Aridell".  Actually it means "the two sons of Aridell" but the founders liked the way "Aridellidies" sounded, didn't want to have to make up a new suffix meaning "children, in general, of", and figured most people wouldn't care.

Do you know what the Aridell was?

They say it's the source.  The place from which all life sprang.  A sacred place.

It was a ship.

Ship?  Like the ones on the eastern ocean?

No.  A space ship.  And not some puny planet hopper either, interstellar.  It went between stars.

That's impossible.

Don't believe you can fly over the firmament?

Even if things hadn't stagnated, it would be hundreds of years before we could even reach the near moon.  It's impossible to go between stars.  The technology doesn't exist.

Doesn't exist anymore.  Did you ever wonder why none of the animals look like us.

Because we're not animals.

Because we're not from here.  Human beings came from elsewhere.  The Aridell was a twelve person exploration ship.  Something went wrong, and when they tried to send out an SOS--

A what?

Cry for help.  When they tried to send it out they discovered that every CRD--

What's with the three letter crap?

Communications Relay Device.  They let you send signals further than you could on your own.

Like the messenger stations?

But in space and with less mirrors.  And no people.  Entirely automated.

You could never automate something like that.

Why did you come here?  It's a crime to be in this place, it's a crime to even know about this place if you're not part of internal security, and even then they don't know where it is, otherwise they would have destroyed it.  So why risk everything to come here?

I want to know the truth.

Well I grew up here, I've read these books, I've listened to recordings, I've accessed computers, I've watched videos, I've looked at pictures, and I know that truth you're looking for.  I'm guessing you know, at most, what three of the five things I just mentioned are, so --rather than having to learn all that crap yourself-- why not listen to me?

Why should I trust you?

I haven't had anyone to tell the story to since I was five.  Why waste this chance with lies?  Will you listen?

Fine.

Thanks.  They couldn't communicate with anyone to get help or repairs, they eventually figured out that there had been some kind of war, and the CRDs were probably destroyed as part of that.  The fact that they hadn't been replaced meant that that part of the frontier had probably been abandoned, and --like I said-- it was an exploration ship.  They were way beyond the frontier.

So no help was coming.

Exactly.  The good news is that they made it to Terra Nova.

The earth mother.

If you want to call it that.  It's not what the words mean.

I know that, but she's the earth mother.

I won't disagree.  Anyway, they were able to land without incident before the ship failed, and they found this world a paradise.  Compatible life.  Which they'd kind of expected, actually.  It was what the exploration had been about.  There were thousands upon thousands of colonized planets in the old empire, not one of them had life compatible with humans before terraforming; the possibility that this one would was what led to the Aridell being launched in the first place.

What do you mean, compatible?

Not at all curious what "terraforming" means?

Earth making.  I'm not stupid.

So you keep on proving, but you are ignorant ---no fault of your own--* so I never know what you'll know.  Anyway, let's get rid of more of that ignorance since that's why you came here.  We can eat a lot of the fruit and a lot of the animals, we can breathe the air.  Terra Nova didn't need to be changed, "earth made" if you like, for people to live here.  That's what compatible means in this context.

Better still, there were no predators and none of the local diseases could touch humans because we were different enough to be incompatible with those.

And predators are?

Animals that hunt down, kill, and eat, other animals.

Proactive scavengers.

I've never thought of it that way.  Yes.

*pause*

With no real dangers, and a safe landing, the crew was safe, unscathed, and could live out their lives as they saw fit.  They just had to decide what they saw fit.  It was as was traditional in those days to have the crew evenly split between men and women.

What about people who were neither?

The founders were many things, and a lot better than the current rulers in a lot of ways, but they were by no means perfect and neither was their culture.  Anyway, even split.

Six women; six men.

Well remembered.  They eventually decided that they'd like to have kids, but they knew that the results could be catastrophic a few generations down the line so they set up a breeding program.  Unlike the current monstrosity participation was volunteer only.

It just so happened that they all volunteered, doubtless helped by the medical technology still available on the ship making having kids a lot easier.

What did they have on the ship?

Well, for one thing, they were able to use various components to create artificial wombs.  No one had to get pregnant, and that makes things a lot less dangerous.  Also, no one had to have sex, which made that a lot less fraught.

You're talking about magic.

No.  Technology the likes of which you or I have never seen.

To avoid genetics becoming unnecessarily linked, every possible pairing was made.

Six per person, thirty six children total.

Good math, but there was a set of twins, so thirty seven.  In the most simplistic theory six kids per person should mean a better than 98% retention of genetic diversity --and, even though they're discrete not continuous, the chromosomes do a pretty good job of following that pattern, binomial and all that-- but that two percent is about, though somewhat less than, a chromosome worth.  Of course chromosomes come in pairs, which changes things a bit.**

Is there a point coming?

With twelve people you'd expect to lose four or five chromosomes in the first generation, ignoring transposons of course, so it's only about a tenth of a person being lost.

Even so, when you've only got 12 people worth of gene pool to go around, losing a tenth of a person is kind of a big deal.  Sure, it's less than a 1% reduction in genetic diversity, but this is before the inbreeding even starts, so you get the idea.

And I'm waiting for you to get on with it.  You've been vaguely hinting that I'll get the answers I came here for if I listen to you drone for long enough.

Everything you want to know; yeah.  First generation, no inbreeding, obviously, second generation could pair off with whomever provided they didn't share a parent.  Breeding program still entirely voluntary as it was intended to be forever.  No one was ever supposed to be coerced into anything.

On with it, you are not getting.

Grammar, you are not doing it right.  Along side the "Let's not inbreed till we absolutely have to, and then only do it as little as possible" part of the plan was a second breeding program to deal with the problems inherent in inbreeding.

The biggest one is that it allows detrimental but non-survival-threatening traits to spread throughout the genepool until the preponderance of them becomes survival-threatening.

So the second program was to try to recognize and weed out those traits in a subgroup.  Since most of the traits in question are recessive it's impossible to be absolutely sure you got rid of them, but you can make semi-decent guesses by looking at the offspring, relatives, relatives of offspring, and so forth . . . under certain conditions, at least.

Thus the general population, whose only rule was as little inbreeding as possible, and the second group to make sure the non-bad genes would survive.

The pure ones.

Yup.  Here's the the thing that should really piss you off: they were never supposed to be set above the rest of us.

What were they supposed to do?

Just make sure the non-crap genes didn't get lost in the shuffle.  Every generation they'd have kids with the rest of us to get those genes back out there so we didn't all end up with autosomal recessive disorders, and with each other to maintain their own population.  Again, all of this was meant to be forever voluntary.

So when they demand conjugal rights to--

They're misusing the word "conjugal", are morally bankrupt, and ought to be shot.

You're violent for a book keeper.

You'd be amazed how much violence there is in books, especially the historical, religious, and historical religious ones.  Also, imagine the possible reasons that I haven't had anyone I could talk to these things about since the age of five.

*pause*

Anyway, that was the set up: General population is made up of almost everyone, special population that exists to preserve and distribute good genes, which members of the general population were supposed to be inducted into, should they want it, if they demonstrated good genes and an apparent lack of bad ones, And everyone lives under whatever government we all agree to provided that said governance has protections and representation for minorities.

What about protecting majorities?

They started as a democracy, I don't think they thought the majority needed protecting.

So what happened?

At some point the "pure ones" looked on the rest of the people and what they saw there disgusted them.  We do have all sorts of problems that they don't.  The argument had something to do with inbreeding reducing intelligence unless you specifically selected for high intelligence or some such.

Records from that period are kind of hazy.  There had been a lot instability leading up to it, in retrospect it's simple to see that the conditions for a coup were ideal, then the records get hazy for a bit, and then my people rebuilt in secret as the "pure ones" tried to erase everything that didn't agree with their divine genetic right to rule.  By which point, as you might guess, the coup had already finished with success.

And that's your answer.  It started out as nothing more than voluntary gene pool maintenance in an attempt to survive --as a species, in the long term-- with an extremely shallow gene pool.  There was no political element, and the "pure ones" weren't supposed to be treated any differently than anyone else except in how they participated, if they so chose, in the ongoing breeding program.

Eventually they decided that, as the bearers of the theoretically good genes, they ought to be in charge, and they used the genealogical records they seized when they took over as a way to enforce their nice little class system.

Sure.  All my questions answered.

I like your sarcasm.  You'd be a good record keeper, but you're after more than that, aren't you?

I thought you knew everything.

Never said that; I just know more than you.

*pause*

The records of how previous revolutionaries were crushed are kept over here.  I'd recommend reading them in depth so you don't repeat their mistakes.

[Exit stage somewhere]

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* This is said without intended offense.  The record keeper grew up in the only library of accurate information on the planet, and for most of that time had only the records for company.  The record keeper could go out and act like a normal member of the under classes, but since any details about self, home, or history could get one arrested if said to the wrong person, most of the record keeper's life has been spent examining the records.

The record keeper assumes that everyone knows less, and further that revolutionary wouldn't be seeking out the records without ignorance of the truth as a driving force.  If revolutionary were not ignorant, it would mean she already knew what she needed to know, so why she have sought out the library?  So record keeper's reasoning goes.

** It has been so long since I did binomial distribution crap that I initially fucked up the odds on chromosome retention in the first generation.  Basically what you want to do is think in pairs (23 of them.)  Then you apply the odds that both members of the pair will be passed on (1-.5^6) as the probability, 23 as the number of trials, and get an expected value of 22.64051.  Now in practice if the the result is the usual 46 that's going to be either 22 or 23 because you can't have a 0.64051 chromosome passed on.  But we need those odds for when we expand to multiple people.

Now, 22.64051 is for the pairs that get their second member (doesn't matter how we choose first or second) so 22.64051 is the expected number of second members.  All pairs get at least one passed on, so we add 23 to find that we expect each person to pass on 45.64051 chromosomes.  Multiply by 12 people.  Now we have an expectation that 547.68612 are passed on in total out of the 46 * 12 = 552 we started with, which means we're losing 4.31388.

Again, you can't have a partial one (well . . . you can, but this math doesn't account for that) so four or five is what we expect to be lost in generation one.  Obviously it's possible none were lost and it's also possible that significantly more were lost.

All of the above assumes 46 chromosome individuals, which one shouldn't, but it's simplified a lot.

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