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How Many People Does It Take To Colonize Another Star System?
Hugh Pickens DOT Com writes: "The nearest star systems — such as our nearest neighbor, Proxima Centauri, which is 4.2 light-years from home — are so far away, reaching them would require a generational starship. Entire generations of people would be born, live, and die before the ship reached its destination. This brings up the question of how many people you need to send on a hypothetical interstellar mission to sustain sufficient genetic diversity. Anthropologist Cameron Smith has calculated how many people would be required to maintain genetic diversity and secure the success of the endeavor. William Gardner-O'Kearney helped Smith build the MATLAB simulations to calculate how many different scenarios would play out during interstellar travel and ran some simulations specially to show why the success of an interstellar mission depends crucially on the starting population size. Gardner-O'Kearny calculated each population's possible trajectory over 300 years, or 30 generations. Because there are a lot of random variables to consider, he calculated the trajectory of each population 10 times, then averaged the results.
A population of 150 people, proposed by John Moore in 2002, is not nearly high enough to maintain genetic variation. Over many generations, inbreeding leads to the loss of more than 80 percent of the original diversity found within the hypothetical gene. A population of 500 people would not be sufficient either, Smith says. "Five hundred people picked at random today from the human population would not probably represent all of human genetic diversity . . . If you're going to seed a planet for its entire future, you want to have as much genetic diversity as possible, because that diversity is your insurance policy for adaptation to new conditions." A starting population of 40,000 people maintains 100 percent of its variation, while the 10,000-person scenario stays relatively stable too. So, Smith concludes that a number between 10,000 and 40,000 is a pretty safe bet when it comes to preserving genetic variation. Luckily, tens of thousands of pioneers wouldn't have to be housed all in one starship. Spreading people out among multiple ships also spreads out the risk. Modular ships could dock together for trade and social gatherings, but travel separately so that disaster for one wouldn't spell disaster for all. 'With 10,000,' Smith says, 'you can set off with good amount of human genetic diversity, survive even a bad disease sweep, and arrive in numbers, perhaps, and diversity sufficient to make a good go at Humanity 2.0.'"
A population of 150 people, proposed by John Moore in 2002, is not nearly high enough to maintain genetic variation. Over many generations, inbreeding leads to the loss of more than 80 percent of the original diversity found within the hypothetical gene. A population of 500 people would not be sufficient either, Smith says. "Five hundred people picked at random today from the human population would not probably represent all of human genetic diversity . . . If you're going to seed a planet for its entire future, you want to have as much genetic diversity as possible, because that diversity is your insurance policy for adaptation to new conditions." A starting population of 40,000 people maintains 100 percent of its variation, while the 10,000-person scenario stays relatively stable too. So, Smith concludes that a number between 10,000 and 40,000 is a pretty safe bet when it comes to preserving genetic variation. Luckily, tens of thousands of pioneers wouldn't have to be housed all in one starship. Spreading people out among multiple ships also spreads out the risk. Modular ships could dock together for trade and social gatherings, but travel separately so that disaster for one wouldn't spell disaster for all. 'With 10,000,' Smith says, 'you can set off with good amount of human genetic diversity, survive even a bad disease sweep, and arrive in numbers, perhaps, and diversity sufficient to make a good go at Humanity 2.0.'"
By the time we have the tech to build a starship we can just ship out as many embryos as we can fit in a freezer. Job done.
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With technology, we can preserve a lot of genetic diversity in frozen embryos, eggs, sperm. So there are ways of mitigating the risk of genetic trait loss with a lower population.
How about a smaller sample of people and a large sperm and egg bank instead?
If it's just genetic diversity you're worried about, why send the people themselves? It seems to me that sending that many people would be a massive over-expenditure of resources. Why not send much more manageable number of people to run the ship and build the initial settlement along with preserved genetic material for a massively larger population. Breed, predominantly, through artificial insemination for the initial generations until you are back to having the desired diversity in the actual living population.
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A lot of people (not us Slashdotters, of course) have the misconception that other solar systems are right next door to ours. So I always illustrate it like this: The fastest spacecrafts we've ever built take about 9 years or so to go from Earth to Pluto. At that rate, they would take about 120,000 years to reach the next closest solar system. I also saw a great illustration once using a quarter (coin), to represent our solar system, and the next solar system being something like two football fields away.
SJW's don't eliminate discrimination. They just expropriate it for themselves.
Five hundred people picked at random today from the human population would not probably represent all of human genetic diversity . . . If you're going to seed a planet for its entire future, you want to have as much genetic diversity as possible, because that diversity is your insurance policy for adaptation to new conditions
when it comes to preserving genetic variation
Except that's not the goal.
If you're talking about colonizing another star system (presumably this is way the fuck after we colonize mars, the moon, IO, Titan, Venus, Murcury, and whatever else we feel like) then little things like genetic diversity upon reaching the target are of little concern.
No, you care about GETTING THERE with enough wits about you that you can continue to function, and set up something to expand your capabilities.
The fight is not to keep the diversity we see on earth circa 2000, but rather the fight is against inbreeding from making everyone retarded to the point where they can no longer function.
Once you get there, and establish colonies, food supply, and your ecosphere can expand past the mothership, you can breed like rabbits and let nature take it's course to overcome whatever detrimental effects that being cooped up in a closed space for 30 generations might have had.
Or every generation could be a fucking clone while on the way there. Seriously, this is colonizing ANOTHER SOLAR SYSTEM. This is WAY OUT THERE. It's science fiction. Just what the hell were you planning of propelling this ship with for 30 years?
Hell, taking the long view, just spreading ANY form of sustainable life is a viable goal for this sort of project. At this scale, "humans" are transient things.
I wonder if they are taking into account whether the people involved will want to procreate with each other. Just because there are enough bodies to maintain adequate diversity, doesn't mean everyone will happily pair up to make that happen. That is a much more difficult calculation. That being said, if you have a short list of potential breeding partners, some people will become less picky.
Ninjas don't carry tic tacs
To me, the question is not really how many people, but how many earthworms, and in general plants, bugs, birds, animals, etc.? At present, we really have no idea what is needed, nor in how much variation within each species, but I suspect the real answer will always be "more that we think."
On a vaguely related note: Assume you send N ships on this voyage. Do you send N copies of the same ship, and hope the design has no fatal flaw (while acknowledging the advantages of parts redundancy) . Or do you send N different designs in the hope that diversity of design is overall more reliable?
While you would clearly be getting volunteers for the start of this task, there is an ethical dillema as far as future generations. Just because parents / grandparents / great-grandparents were totally OK living their entire lives in what would be a fairly finite space, it doesn't mean some members of a future generation wouldn't consider it torture. I guess it might be hard for me to see things from their eyes since they would be born into it, but I'm thinking that after I got to learn some history and see some videos / pictures of Earth, I'd be pretty unhappy stuck on a spaceship forever. I wonder how many would refuse to breed and do the same to their offspring (which would screw up the "diversity", or decide to turn back, or just go stark-raving-mad and murder someone or everyone (destroy the ship), and then your genetic diversity is REALLY screwed.
Why not just allow for inbreeding and do continuous genetic testing on all embryos generated, terminating those that will turn into West Virginians?
Why not just allow inbreeding? It's how we fucking colonized Earth. Genetic diversity isn't something to strive for, it's simply a result of a population surviving long enough in different circumstances (from diet to weather to disease). Absolutely none of the issues our current genetic diversity handles will be an issue for a colonization program. All people chosen will be screened appropriately so we'll know they're all decently healthy, and all potential catastrophic problems will be completely unlike those encountered (and survived) on Earth by humans before the advent of clothing, medicine, etc. The risk of inbreeding creating disfigured/disabled/impaired offspring is really quite low, especially if you screen for known issues in advance. It's a taboo with no basis in science. Yes, bad shit can happen when you start with bad genes, but that's just as likely as good shit happening when you start with good genes. Inbreeding is how all populations of sexual species bootstrap. When you get right down to it, ANYONE you marry is your cousin, and it doesn't fucking matter.
Early human population dwindled to as few as 2000 individuals with most living in isolated pockets of a few hundred. Given enough time the population and genetic variability rebounded. Colonization of other worlds is most definitely a long-term project and while a bigger sample might give you better chances its probably possible with far fewer individuals.
How many people does it take to colonize this star system? Apparently more than the 6 Billion we have on Earth, since we haven't even bothered to get off this damn rock.
Send people to Mars first, then worry about Alpha Centauri (which is a terrible place to send people to anyway. The only thing there is a backwaters galactic planning council office)
--Joe
Assuming the closest is even viable, which it probably isn't, 4.2 Light Years = 39735067984839.36 Kilometers. The fastest thing (only thing) man has sent out of our solar system is Voyager 1, which at its current speed, if it was pointed in the right direction would take about 73,775 years to reach the target. Considering you probably don't want to run into it at that speed, you will have to accelerate and decelerate. Which it doesn't have the fuel for (never mind its RTG energy source is only good for 60-80 years), but even if it did would roughly double the time to reach the intended target to about 147,550 years. OK well that's not quite true, it would only add an insignificant amount of time because not a lot of time was actually spent to accelerate in the first place. However in the example below where you do not coast for tens of thousands of years, and accelerate til the midway point and then immediately start to decelerate it would double whatever you speed VS distance is anyway.
Sure you could accelerate and decelerate much harder than that to get there much faster, approaching whatever value of c is currently capable at launch. However by any measure, unless some magic energy source and method of propulsion is devised, the required energy at least at today's standards would require carting around the hydrogen energy mass of our sun for the trip. Some other methods of insitu material gathering such as ram scoops picking up interstellar dust are as likely as the fiction, as again unless some dark matter type thing which is everywhere (presumably) is harnessed, the amount of mass available is pretty low, space as it turns out is pretty damn empty.
Not to mention the weirdness of relative time as one approaches c on a ship compared to Earth, as while it may take less than the 75k years voyager would, here on Earth many more years will have elapsed. As to how many, I have no idea, that is beyond my math calculating ability (as is generally most of what I have currently written I am sure will be pointed out).
Never mind trying to maintain a ship, machinery, technology, or even a society that long!
More likely colonization will involve self replicating and regenerating robotic ship carrying a genetic payload and an informational database (likely with a terra forming mission proceeding it). Which would be more like favorable seeding for similar evolution and life to occur, than an actual "colony". Then again, that would also require pretty adaptive programming and AI, which would likely mean we would probably be fertilizer for our robotic overlords petunia plants.
So I guess I am saying as a thought experiment it is sort of interesting, but at this point (or any really foreseeable point in our future), it is all a bit far fetched by even the loosest standards.
2) It assumes that transportation will take 100's of years. Within 100 years, our space technology should be able to deliver 10 people 4 light years away (one way trip), in no more than 50 years travel time. That is two generations.
3) There is no reason to select people 'randomly', we can easily intentionally select people non-randomly, making sure that they have minimal DNA in common. Often 'random' ensures that weird coincidences happen.
4) The Toba theory claims that humans had a bottleneck of 3,000-10,000 individuals. 10,000 is a HIGH end, not a low end of what we need.
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Generation ships are impossible** for humans, which will likely cause our extinction.
Although technically and logically, it is not an insurmountable problem. You need a small crew, 6 or 7 women per generation. A high number of frozen male and double that many frozen female embryos (which we will assume are viable forever, though we don't know).
All crew members birth one daughter. If one is not successful, one crew member births 2 daufghters.
They are raised to be the next generation of crew.
Many generations later, strict population control (through gender homogeny) 6 or 7 women will land on target planet (or more likely orbit it)
Exploratory team of males/females are raised during the last "transport" generation, then they are sent on a lander as a pilot program, meanwhile another generation of female crew is needed.
If pilot program is successful and either farming is not needed (if gatherer lifestyle is possible on destination) either send more landers, or land the craft and begin large scale birth-rate increases, with every female birthing 6 or more embryos as health allows.
While using up the rest of the embryos (which will be an exponential thing) Ease humanity into a reproductive lifestyle, as it will be culturally foreign to them.
**This requires so much space culture cooperation and "unethical" planning that humans would never do it. We are more likely to spend all of our natural resources to make a GIANT space ship that crashes and kills thousands of people instead, because of the "religion/culture" problem, which is unsolvable.
Sending meat bags into space is not very practical at all. It's more likely that we'll develop nano-factories and the capability of offloading intelligence into machines. Then we can just create intelligent space drones that replicate themselves as they go along and thus populate the galaxy.
This is actually one of the reasons why some think there is no extraterrestial life advanced enough to pull this off, as we would have noticed it by now. The reasoning behind this is that any society that has such capabilities more than likely destroyed itself before being able to reach this state. Of course, we might just be the first in our universe to pull this off, but don't count on it.
Ten women for every man and they woman ..."I hasten to add that since each man will be required to do prodigious... service along these lines, the women will have to be selected for their sexual characteristics which will have to be of a highly stimulating nature. "
Just don't bring the mosquitoes. Or the Toy Poodles
Send a sperm bank and a handful of (very dedicated) women, deter first cousins or closer from breeding, population remains low it doesn't expand until the ship nears it's destination, it then expands at a predetermined rate to provide the workforce needed to construct the colony upon arrival.
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