beccaelizabeth: my Watcher tattoo in blue, plus Be in red Buffy style font (Default)
[personal profile] beccaelizabeth
So, I read a story where the Earth's entire colonisation effort was something like thirty women, and they were going to get implanted with preserved embryos on their first day there because they might be the whole hope of survival for the human race.

... which bothers me on several levels.

They were all women because they needed to be surrogates for as many babies as possible. But that just needs a functioning uterus. So, choose for half your mission trans men who are willing and able.

The timing looks ridiculous. Your entire colony being pregnant at once means your entire colony being huge with child at once, including whoever you have by way of midwives, obstetricians, and neonate paediatricians, doctors and nurses. ... also, thirty isn't enough to get a modern hospital going, so good luck having all the medical expertise you need to keep mortality down to modern non USA levels.

It only might maybe possibly make sense if there was a hard limit they were heading into. So, I looked up how long embryos can be cryopreserved for. And in the top four google results science says something fuzzy, because the technique has only existed thirty years, so the upper limit on what they've got data for is thirty, but after that long the donors are rather unlikely to come back and use them, so in practice they haven't tested that. I kept finding thirteen, for practical experience. But legally Britain and Australia both say maximum ten, with possible extensions in the UK if you fit certain criteria or, I guess, have a good lawyer. So data for longer than ten years would be scarce.

Ten, fifteen, or even thirty years to get to another planet is actually a limit you could run into. Or over. If by the time you arrive you're breaking new limits in cryopreservation, a certain sense of urgency might prevail.

But the science also say in theory that once they're frozen they aren't changing. Storage should, theory says, be indefinite.

But keeping them frozen needs work. Needs new liquid nitrogen every week, though automated systems exist. If it goes wrong it gets up to use it or lose it temperatures in less than 24 hours. If the whole ship is hibernating, they either need to be able to wake up fast, or they're going to lose some. If a maintenance crew stays awake, there will be someone whose job is to check the freezers are frozen. And not leaking in such a way as to screw up the nitrogen balance of the ship's life support. Huh, would you use another liquid, to match your life support? Either way, it's not the most complex looking aspect of starship maintenance, but if it goes wrong enough you lose your colony just the same.

And here we have reason the first why bringing zero cis men seems to me strange: no backup plan. I mean, maybe you can bring sperm, but that'll have all the same life support needs. Humans are the only way to generate more of that resource.

A colony that tiny couldn't bring sufficient genetic diversity walking around though.

You'd get weird new social effects if you had so much as a generation without any men. ... you might want those.

You'd also need to screen out heterosexuals who value relationships in the first generation if you didn't want them to get miserable. Bringing trans men means you wouldn't need to choose only wlw, as long as the hets understand pregnant men are men.

... possibly we need to recruit from mpreg fandom?

You want a bigger crew. I mean if you want to build houses when you get there you want a bigger crew. To run childcare and schools you definitely want a bigger crew. If you're going to keep everyone continuously pregnant you'll need to cope with school years at least as large as the original colony. ... I purely don't see that working, how are they envisaging caring for thirty toddlers and thirty infants while all thirty of them are pregnant? I mean once they get big enough to babysit you've got a production line going, but before that?

Start with something like the old school Orion and you start with a crew of 150 to 200 even if they're all awake in their own individual quarters. Turns out nuclear bombs can make you go zoom and the way they do it bigger is actually better, to a point. It's real unlikely to fly in ordinary circumstances since the launch fallout would kill people, but in the story the urgency was compounded by maybe being the only humans left alive, so we can assume enough of Earth would make an exception for a last ditch evacuation that big nuclear pulse ships become plausible. Ish.

... yes I know there's whole new layers of problem and time to nearest star system is still excessive at around 44 years, let alone time to *habitable* star systems, at 0.1c.

... if published stories can skip the whole journey, so can I. Even though propulsion method and payload size is crucial to colony size, how many personnel, how many embryos each, and how long they all have to be preserved to even work when they get there.

... I much prefer playing with Stargates, but with those if you need more genetic diversity you hop over to another planet, so they're not exactly relevant here.

If all you can get is all you can pack, colony in a bottle, then viability depends on genetic variety and stuff that's just theory right now.

the range in that one article goes from 150 with very careful control of breeding to 10,000 if you're careful and never lose any before optimal reproduction. 40,000 is what you really want.

But if you read down the page their graphs assume having one child each? I guess on a generation ship you need that restriction, but on a planet, no.

So the number takes a lot of crunching and is somewhere above 150 and below 40K.


is the earlier math that reckons the magic number is 160. (not 150 as the other article says, which don't speak well as to accuracy)

but the genetic diversity is fine *if* they reconnect with other human populations later in the sim, which isn't what we're talking about here.

I reckon the only thing I'll learn by reading around more is that the initial assumptions matter a lot. And I won't know the math to tweak them.

One important bit is that a lower number requires far less personal freedom of choice if you want the colony to survive. If genetic preservation rules out marrying freely, you need heavy social engineering. I'm thinking moeity? Just for starters. You'd have lines that Do Not Cross. I mean, you'd also be tole who to breed with by the computer, that would work. Possibly you'd seperate romance and breeding? Lots of social stuff.

Obviously if everyone is women you do what the computer tells you and grow whatever was frozen well enough. Er, whoever.

How long would they keep up the Ladies Only plan?

I mean if the plan is to get as much genetic diversity as possible out of the frozen embryo stores in the ship and there's some kind of time limit on that, you'd want to make sure there's plenty of wombs to go around. Would you get everyone out in a single generation?

If you're aiming for ten thousand colonists, even if you have multiple births routinely and soak the risk, that needs a really big first gen pool. So you'd want to keep up the embryos plan for multiple generations, without losing any of the earlier generations. You could do that with donor sperm and embryos. Or with a lot of social stuff to make sure your great grandchildren are still interested in decanting old world people.

also one of the mathier pieces says "the consequences of the increased medical risks of late childbirth have not yet been considered." It wanted to stretch the generations on a generation ship by having kids around 40, but, wow is that a biggie to leave out of your math. I mean, your chances change substantially over time.
has a little table that is really, really relevant if you're planning to implant your hopes for the future.

The frozen embryos are all the genetic diversity you colony will ever have.

If there's a 90% chance of the embryo surviving cryo (I read that figure many links ago, it might be not quite... huh, other links say lower even) then you need to bring colony*1.1 embryos. Simples if colony is 160, not so simples if 40K. And if you optimise for diversity any given donor has only a 90% chance of, well, getting a chance.
has more confusing graphs for live births per embryo transfer.

There's a six year difference between 68% live births and 37%.

You want all your wombs to be under 35 then.

But you also need memetic diversity, to pack as much human expertise as you can in one can, so you might want to put a lot of PhDs and MDs in there. And that kind of learning takes time. So you're not talking about 15 years of optimal fertility, it'll be much less than that.

... also, imagine looking after 15 children each. Wow that's too many.

But optimal time between pregnancies as per google is 18 months, or risk premature babies, so you don't get 15 babies in 15 years anyway. More like six or seven. If they all go to term.

If you want 10K gene lines you need 10K*1.1*1.4 at least of embryos. That's 15400. Or around 18000 if you account for more lost pregnancies if everyone waits.

That's a lot of stored embryos.

You'd nearly double your cryopreservation needs.

Also legal standards for storage say you need backup containers for if the first ones fail. Don't think that maths right across interstellar distances, you'd just pack as many extra as you had room for, in case losses were worse than expected.

After decades to centuries in space riding nuclear bombs? You're going to have damage that earth based facilities and people do not.

Mean time to failure of all your equipment gets critical. I think that 90% survival is assuming perfect equipment function. You'd need to assume partial failure over that long.

I know embryos are really small but that still means bringing even more.

And just to get back to, some estimates say 10K babies need born to get sufficient diversity.

If every woman has 7 babies you'd need a starting generation of around 1500 women.

If anyone gets fed up before 7 live births you would need more.

If you start with a generation of 30 women of unspecified ages and need to give birth to ten thousand? I can see how that seems urgent. I don't see how that seems possible.

Maybe they've seen the 150 estimate and think they only need to make the second generation be 150 people before civilisation can glide on... but that's still five babies each.

200 women having 7 babies each gets the colony to 1400 in one generation. If that one generation is all women and they do the same thing again, 9800 for the second gen. To preserve genetic lines they'd need to have some sperm so those 1400 were represented later, or have other expedients, say twinning them to be born again later. ... it's science fiction, and stuff can happen. 9800 is nearly enough so the grandchildren would only need to have a few cryo preserved kids, but if there's room to bring more then more is better, as long as no lines die out. If the later generations start reproducing at 20 you might only need storage for sixty ish years after planetfall.

That's sixty on top of the length of the journey.

And assuming all the women got there with their reproductive organs still behaving as if they're under 35, which seems like a really specific need for a newly developed technology used to sleep between the stars.

If not, generation ship involves birthing enough women to start all this once they get there. That stable 160 the first math talked about. The new genetics encountered at the end of the journey would be the embryo pool.

But only the first 200 would be volunteers who up front believe themselves willing to act that way. The future survival of the human race would depend on their reproductive behaviour. Their choices would be severely constrained.

And to get all the embryos out of storage in the shortest generations they'd need to get their daughters to act the same way. Which seems... unlikely.

Diversity of behaviour would increase the time taken to get the colony up to size. And therefore the time in storage the embryos would need to survive.

There's some urgency then, sure, but it still makes absolutely no sense to get everyone pregnant as soon as they land. At least stagger the births so the medical staff aren't going into labour around the same time as everyone else. Make everyone be in different trimesters so they don't all go less mobile at once. ... learn first hand what it's like taking car of a baby before committing to taking care of one each for the next twenty years.

... that would be an important selection criterion for the crew. As well as engineering, childcare experience. In big families and/or busy daycares.

Hard science fiction that sets out a space colony as that baby focused without thinking through how they're actually going to feed the babies is just bad.

I mean, maybe they all get pregnant before they've got a crop going on the grounds that if they starve to death it's all one anyway, but... no.

Also the science problem in the novellette I read was far less interesting to me than the social consequences of the background setup. Humanity is now 100% women, drawn from only three cultures, and planning to have as many babies as possible for the rest of their lives. Play that through for een one generation and who do you get?

And if they choose to have only daughters so there can be more births from stored embryos faster, how do the daughters feel about it?

And at what point do they decide to introduce men?

Well, around when they start using stored sperm to make sure the first gen gene lines persist too, unless they get selective there too. It'd last longer if they used more fetility tech and planned those embryos too. But if some of the births are random and some from old Earth, what kind of social divisions do you get?

And almost all the ethnic diversity was in the stored embryos. Possibly racially diverse, but, the crew was Japanese, Indian and American, so if I've got the distinction right that's a limited set of ethnicities. And the story had an argue because the Americans were biggest and had decided English was the language of the new world.

There'd be a bunch of relevant expertise about inter racial and international adoption. For the embryo babies. Who both are and aren't adopted.

I mean personally I'd start with cultures with histories of successful island life and empty island colonisation, not that those are going to be uncolonised themselves, but still, people with a tight community and lots of cooperation in their culture. Send awake people who are most likely to cope with the world consisting of 200 people. But preserving cultural diversity would be a huge big deal. However much data storage you had it wouldn't be like bringing Earth with you. You could pack Ao3 and all associated shows, but you couldn't bring much of fandom, much less establish a civilisation big enough to reinvent Hollywood in forseeable timespans. Language you started with would matter.

Sending anyone would require filtering for people that can work in small groups with no outsider input or new faces. For the rest of their lives.

... even nuns don't really do that here. The isolation would be fascinating.

I think one big factor for viable colony size calculations is something like, if we send people who act pretty much like people of that cultural background do, how many do we need?

Like, we'd need to include murder rates from somewhere.

You do not get perfectly behaved people. No matter how you filter them at the start.

And the cultural changes would be massive even in the first generation kids. I mean how many immigrants feel like they don't really understand their children?

And if the future of the human race depends on women's reproductive choices, it's kind of more likely to work if you start with what those choices *actually* tend to be. First gen you could filter for people that want big families - though not for people that want big families once they start having them and are surrounded by them - but second gen will do as they will.

How do you design a colony socially so it does what you need genetically?

Clue: you do not stick thirty women on a one way trip and keep them pregnant from the first month they get there.

Hard science needs to at least glance at soft science or it requires the ridiculous.
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