Pregnancy on Generation ship

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Pregnancy on Generation ship

Postby caters on July 24th, 2017, 8:38 pm 

I was thinking about the generation ship in my sci fi story and I am working on a book about specifically the generation ship.

I thought this thing about pregnancy deserved a topic here so here I go.

Starting with a few weeks before mating, half of the people on the generation ship will stay diurnal while the other half transition over those few weeks from diurnal to nocturnal. The aliens on the generation ship have already mastered this but this is partly due to how their sleep schedule is determined by photosensitive proteins and genetics.

This all happens in the primary sleeping quarters. The secondary ones are reserved for mating.

Now Diurnal-Diurnal couples will most likely have Diurnal children but there is a possibility that their children will be Nocturnal instead. And very little emotional upset occurs(at least that caused by sleep schedule)

Nocturnal-Nocturnal couples are similar in the fact that very little emotional upset occurs.

Diurnal-Nocturnal couples on the other hand can only have sex during the 2 twilights(morning and evening) because those are the only times when both the diurnal humans and the nocturnal humans are awake.

When the time for mating comes, each M-F pair will be selected randomly to increase genetic diversity. Once those pairs are selected there can't be any deviation from that for a week(fertile window). Now of course this could cause issues like for example there is an equal chance that a woman will be in her fertile window and that a woman will be on her period.

But anyway, after that 1 week everyone goes back to sleeping in the primary sleeping quarters.

2 weeks later all the women that aren't on their period head to the medical bay for pregnancy tests. Those that come up negative are asked to come back in a week if they still have a missed period. If their period comes within that 1 week, it is a true negative. If however the test comes up positive or a transvaginal ultrasound shows an embryo, that negative was false. Of course there is a grey area. Very rare but possible is there being no sign of pregnancy via either pregnancy test or symptoms(known as cryptic pregnancy) until labor. And then those women with cryptic pregnancy could easily be mistaken for those people with appendicitis.

A few months later they are tested again but this time to see if the baby has any external defects. If the baby does have external defects, there are 2 options. 1 option is for the baby to adapt to the defect(like for example hand walking if a leg is missing). The other option is for the aliens to fix the external defect which could be as simple as cutting an extra limb off and skin grafting or as complicated as forming a new limb for several years.

After birth, all babies are tested for internal defects and if there are internal defects, they are diverted right to surgery to fix it. They have all kinds of machinery to sustain homeostasis during surgery.

Do you think that this is reasonable or not and if not, why not? I certainly think it is reasonable.
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Re: Pregnancy on Generation ship

Postby BioWizard on November 12th, 2017, 7:44 am 

I didn’t the premise for why the population needs to be split into nocturnal and diurnal some weeks before mating. And selecting mates at random doesn’t necessarily increase genetic diversity. Selecting them based on genetic distance does.

By the way, have you never stayed up all might “mating” (or heard stories about it)? You don’t have to become fully nocturnal to do it once in a while. Definitely worth the next day grogginess.
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Re: Pregnancy on Generation ship

Postby caters on November 12th, 2017, 7:18 pm 

But randomness increases the chance of high genetic distance and decreases the chance of low genetic distance for any given male-female pair. And that change to nocturnal is several weeks before mating so that should give plenty of time to adapt to it. Besides, doing tons of genetic testing I don't think is worth it for a generation ship with thousands of people unless they want to absolutely make sure that there is no inbreeding(which is pretty much impossible for large populations).

Randomness will give the impression that genetic diversity increased because most often it would if left to randomness. Just like how the chances of you getting several 1s in a row in an irrational number are infinitesimally low(because of infinite digits), the chances of getting a pair of siblings or other closely related pair when randomly selecting people is very low and gets lower and lower as population increases.
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Re: Pregnancy on Generation ship

Postby BioWizard on November 12th, 2017, 7:53 pm 

caters » 12 Nov 2017 06:18 pm wrote:But randomness increases the chance of high genetic distance and decreases the chance of low genetic distance for any given male-female pair.


Not as much as actively selecting mates in a manner that maximizes genetic distance between them.

Imagine you have bag of green and red balls mixed together. You need to draw two at a time. Which will allow you to draw two differently colored balls more frequently, grabbing two randomly or selectively picking one green ball and one red ball?

Same concept applies to selecting mates. When you select them to maximize genetic diversity, you get more mixing than random picking. And the smaller and more homogenous your population is, the better you do with active matching by genetic distance.

And that change to nocturnal is several weeks before mating so that should give plenty of time to adapt to it. Besides, doing tons of genetic testing I don't think is worth it for a generation ship with thousands of people unless they want to absolutely make sure that there is no inbreeding(which is pretty much impossible for large populations).


I guess I don’t see how this in itself would influence inbreeding.

Randomness will give the impression that genetic diversity increased because most often it would if left to randomness. Just like how the chances of you getting several 1s in a row in an irrational number are infinitesimally low(because of infinite digits), the chances of getting a pair of siblings or other closely related pair when randomly selecting people is very low and gets lower and lower as population increases.


Not really. See my comment above.
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