Colony Ships

[Battlehymn Republic]

Does anyone know any good texts or sites that have to do with the sci-fi notion of intergenerational colony ships, where the people live aboard the ship in daily life as opposed to sleeping cryogenically?

What's the minimum population size needed to prevent genetic drift?

[CaptainChewbacca]

Does anyone know any good texts or sites that have to do with the sci-fi notion of intergenerational colony ships, where the people live aboard the ship in daily life as opposed to sleeping cryogenically?

What's the minimum population size needed to prevent genetic drift?

Technically, the minimum population you need is about 30 mating couples. I'd go a bit higher, though.

[Zor]

Does anyone know any good texts or sites that have to do with the sci-fi notion of intergenerational colony ships, where the people live aboard the ship in daily life as opposed to sleeping cryogenically?

What's the minimum population size needed to prevent genetic drift?

Generally for a stable population 500 individuals is the given minimum i get. For generational ships to sustain, i would say a cylindrical grav equiped habitation/agricultural cylender about 100 meters in diameter and 500 meters long should be suffisiant to support said group so long as they maintain proper population growth control durring the flight. Industry for producing replacement parts should be built outside

For the Colony ship itself, for STL Colony ships i generally set the starting length at a kilometer. Atomic Rocket is a good websight on this matter.

Zor

[Sea Skimmer]

Potentially a stock of frozen embryos carried onboard (not sure how long those last) could provide for enormous genetic diversity among a relatively small population.

[drachefly]

If you can find it, the tail end of Asimov's book Extraterrestrial Civilizations deals with such ships.

Keep in mind, too, that a generational traveling space colony may not be centralized in one ship for a variety of reasons. Principal among these is redundancy -- the 'all eggs in one basket' thing.

To put it another way, engineers are often told "how many 9's are needed"
in other words, does something have to work 99% of the time? (2 nines) 99.99% of the time? (4 nines), etc. And among the time it's down, how much of it will be unexpected, how much planned, and how long are the gaps?

Well, a space colony can't afford to have ANY down time. It just has to work. This gets a hell of a lot easier to arrange if you can shuffle all the people off of one ship so IT can be down while the colony as a whole is not.
The need for stability against catastrophe is obvious, but even for planned down-time it helps a lot. Need to really thoroughly irradiate to get rid of mutant fungus or something? That's a lot easier with two colony ships than one -- everyone having to live in space suits for a few days is a pain in the neck.

[Ariphaos]

Technically, the minimum population you need is about 30 mating couples. I'd go a bit higher, though.

My information is several years old, but this does not work indefinitely. If you keep the population at ~64 inbreeding problems will still arise even if you somehow breed them perfectly (which will be a difficult task).

Thus Zor's comment about 500 people. I'd probably shoot for two to five thousand, myself.

[Adrian Laguna]

The entirety of humanity outside of Africa arose from one group of some 150-300 people. That's including children, the elderly, and the dumbass who destroyed his balls while fishing (ie, people who can't mate).

[Metatwaddle]

The entirety of humanity outside of Africa arose from one group of some 150-300 people. That's including children, the elderly, and the dumbass who destroyed his balls while fishing (ie, people who can't mate).

O_O Where did you read that?

[Adrian Laguna]

The dumbass coment was a lame joke.

The rest was derived from genetic analysis of the human population around ten years ago, maybe less. A Discovery channel special titled "the real Eve" explained it all. The title of the program refers to the fact that when you have a small population, eventually all its descendants become related to a single female. I forget what the name of the process is, but it happened with the humans the left Africa. According to the theory, it was just one group that crossed the straight between the Horn of Africa and Yemen. Back then the seas were considerably lower, and they probably crossed becasue they could see that Here (Africa) = Dry and brown, and there (Yemen coast) = Wet and green.

[GrandMasterTerwynn]

The dumbass coment was a lame joke.

The rest was derived from genetic analysis of the human population around ten years ago, maybe less. A Discovery channel special titled "the real Eve" explained it all. The title of the program refers to the fact that when you have a small population, eventually all its descendants become related to a single female. I forget what the name of the process is, but it happened with the humans the left Africa. According to the theory, it was just one group that crossed the straight between the Horn of Africa and Yemen. Back then the seas were considerably lower, and they probably crossed becasue they could see that Here (Africa) = Dry and brown, and there (Yemen coast) = Wet and green.

The size of the human population which gave rise to the rest of us was more like 1000 to 10,000 individuals. One of the theories advanced to explain this is the aftereffects of a super-volcano. Roughly 70,000 to 75,000 years ago, the Toba caldera in Indonesia erupted, covering the entire Indian subcontinent in a minimum of 15 centimeters (six inches) of ash. The result was a global volcanic winter lasting several years, and roughly a millenium of colder, drier climates. This had the effect of fragmenting and isolating human populations. One of these populations was better at surviving or was more favorably located than other human populations at the time. The end result being that all humans alive today descend from that particular population.

[Ariphaos]

The size of the human population which gave rise to the rest of us was more like 1000 to 10,000 individuals. One of the theories advanced to explain this is the aftereffects of a super-volcano. Roughly 70,000 to 75,000 years ago, the Toba caldera in Indonesia erupted, covering the entire Indian subcontinent in a minimum of 15 centimeters (six inches) of ash. The result was a global volcanic winter lasting several years, and roughly a millenium of colder, drier climates. This had the effect of fragmenting and isolating human populations. One of these populations was better at surviving or was more favorably located than other human populations at the time. The end result being that all humans alive today descend from that particular population.

IIRC, it's been narrowed down to about 2,000 people. The Y-Adam also heralds from this period. However, the L3 genetic subgroup, which makes up North Africans, East Africans, and everyone outside of Africa, is also the shallowest of all four major subgroups, thus Adrian's comment.

However, the ~200 people that made up that group were not population-limited, allowing defects to be bred out. So it doesn't entirely apply to a colony ship's methods.

[Adrian Laguna]

The size of the human population which gave rise to the rest of us was more like 1000 to 10,000 individuals.

That would be the anscestors of the entire human population. I'm talking about the anscestors of only the group that left Africa. The African continent has the greatest genetic diversity among its population.

[Adrian Laguna]

Edit - I should add that my position is based entirely on what I remember of "The Real Eve". So while I'm not pulling things out of my ass, I also don't have a very strong and well researched position. Take that as you will.

[DPDarkPrimus]

According to the game manual, the colony ship Marathon had an original crew of 50 senior staff, 1150 officers and 24,000 civilians. Some were kept in cryogenic stasis, but most lived and worked out their lives. The future generations of those people came to be known as "Bobs", or "born on board", which is quite the endearing term.

[drachefly]

Also, if you have the tech to run a space colony, it seems to me likely that you'll have the tech to keep the really nasty recessive pairs from doubling up.

[haard]

Also, if you have the tech to run a space colony, it seems to me likely that you'll have the tech to keep the really nasty recessive pairs from doubling up.

Why is that? You don't need much knowledge of genetics to build a spaceship, after all...?


And this might just be me, but I have the feeling that a STL colony ship could very well be built today if enough money was put into it.

[drachefly]

In addition to building the rockets, you need to have enough biological knowledge to construct a whole biosphere, even a partially artificial one. That suggests substantial knowledge of the life sciences.

But more in particular, supposing these are human colonies (which it seems most people had been supposing so far), then we are already not far from such technology at the present time; certainly by the time we're ready to build an intergenerational starship, we'll have mapped our genome well enough to figure out many of the harmful recessive gene pairs. And in particular, after a few generations, if they missed any, they'll have found them.