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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.'"
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?
The point of exploring the stars will never be to "reduce the surplus population". That's not likely to be a real problem in any case.
The point is to broaden humanity's knowledge, perspective, and diversity. To make us, collectively, more than we are now.
But the stars are out of reach without some revolutionary new understanding of physics. The energy budget for interstellar travel is insane, assuming we want to get somewhere within a generation. It's far beyond workable fusion power needed for a starship: either some sort of warp drive, or antimatter fuel and a rocket with near-light speed exhaust.
The nice thing is, relativity means you can travel ridiculously long distances in subjective time and with an energy budget not much worse than going 100 light years. Humanity on Earth, not to mention the Sun, may be long gone when you get there, but you can visit other galaxies if only you had a magical power source.
Socialism: a lie told by totalitarians and believed by fools.
to be honest what is the use of this? Why do we want embryos on an other planet. Having to much people on earth won't be solved by sending embryos to other planet... As long as they can't send a large group of people in a short time to an other planet. This whole traveling to other planets is useless...
Redundancy. Overpopulation is not the reason -- that's a self-correcting problem.
Having all of humanity stuck on a single planet in a single solar system leaves mankind open to extinction from a rare planet ending or even a more rare solar system ending event. Though we probably need to get out of the Galaxy for true redundancy. I don't think there's any way to avoid the eventual end of the universe, whether its ends in a big freeze or big crunch...But we have a bit of time before that happens, so it can be left for future generations, as long as we don't end up killing ourselves or depleting our resources before we can get off the planet.
And who says, we didn't already do this? Send out lots of ships to other planets. After that we got some water problems, like Noah's story. After that only a few people survived, started to multiply and created a new civilization. Those people we send out there, are now living happily. And yes, there comes a bunch of embryo's again....
I'm pretty sure the fossil record is complete enough to rule out modern humans suddenly popping up from seeded embryos.
Reminds me of Tau Zero. You can outlive the universe if you can squeeze yourself close enough to the speed of light...
We don't have a state-run media we have a media-run state.
I'm skeptical of those numbers anyway: There have been times where the total number of humans was less than 40k with some speculation that there were as few as 2k for a while. That discounts, say, early settles to regions that then became the native people. How large a group traveled through the Bering Strait to the Americas? With current knowledge, we could screen the initial people for genetic diseases and organize breeding programs to maintain diversity, so we could probably be successful with even less.
Anyways, the ability to freeze bits (sperm, eggs, embryos) already exists and the projected lifetime of sperm at least would easily cover the journey plus the formative years. Heck, it's probably a better solution than legions of people even from a purely genetic perspective as you could probably better control radiation damage.
So that means genetics aren't really going to be as important as:
*) Builders - You aren't going to grandma's. You'll need able-bodies people to build you colony. Robots can help, but it's still going to require a decent crew. Even if you don't maintain this size group throughout the journey, you'll need it when you arrive, meaning the ship needs to have facilities for them to grow up in.
*) Parents - You need to keep people alive to teach new people what being people is. Books and other media will help, but you need a decent assortment to give an understanding of 'society' and prevent one bad egg over the 300 years from spoiling the bunch.
*) Society - Kinda tied to the last point, but you can't just have 10 people playing poker for 300 years. You need some ability to socialize, have friends, create, consume, etc.
I'd side with the anthropologist on this one: 150ish, a small village worth. Genetics are basically a solved problem and pretty much a footnote on the laundry list of problems that colonizing would face. Heck we don't even know if Proxima Centauri has a planet!