Researchers are trying to figure out the ideal number of people needed to create a viable population for multi-generational space travel. They?ve decided it needs to be 160 people. But with some social engineering it might even be possible to reduce this to 80.
Anthropologist John Moore of the University of Florida wondered how future humans might successfully undertake century-long journeys out into space. Other scientists have concentrated on freezing people with cryogenics or taking along sperm banks, but Moore says, ?the ?right stuff? for a journey into space is the family?a million-year-old institution designed to assist reproduction.?
Moore has previously studied small migrating populations of early humans and has developed simulation software called Ethnopop that analyzes the reproductive viability of small groups. A space trip of 200 years would perhaps take eight to 10 generations, and for this, his calculations suggest a minimum number of 160 people are needed to maintain a stable population. This would produce around 10 potential marriage partners per person, he says, and if this seems too small a number, ?think about how many people you dated before you got married.?
Room would be at a premium on any spacecraft and reducing the number of people initially required might be desirable. Moore suggests two ways to accomplish this. The first is to begin with young childless couples, the way Polynesian seafaring colonists once did. The second is to ask the space crew to postpone reproduction until the woman is 35 to 40 years old, creating longer time gaps between the generations. This results in a stable population of just 80 but the consequences of the increased medical risks of late childbirth have to be considered.
Small populations can suffer a damaging reduction in genetic diversity due to inbreeding, says Dennis O?Rourke of the University of Utah. He considered the same 10-generation, 200-year journey as Moore did, looking at both genetic drift and inbreeding, and found there wasn?t a problem. ?The decrease in genetic variation is actually quite small and less than found in some successful small populations on Earth,? he says. ?It would not be a significant factor as long as the space travelers come home or interact with other humans at the end of the 200 year period.?
O'Rourke believes that a more serious concern would be the presence of potentially damaging genotypes in the initial space pioneers. Genetic screening might be needed when choosing the first space colonists. He says, ?Any harmful recessive characteristics might lead to increased healthcare loads which would deplete scarce resources.?
A final concern is the possibility of infighting. Small communities isolated for long periods at research stations in Antarctic have shown how small conflicts can quickly escalate. But Moore says, ?Some small island communities on Earth have lived in peace and harmony for thousands of years because they have developed ways of solving conflicts. These [solutions] are not taken to Antarctica.?
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Unlike today?s relatively small space stations, the craft of tomorrow will have to be the size of small cities and will be constructed in orbit. Transporting large numbers of people across the galaxy to new worlds will require vast ships driven by gigantic sails, blown across deep space by intense bursts from a giant laser. American space agency researcher Dr. Geoffrey Landis says, ?You could have a sail that is perhaps hundreds of miles across. It would be huge but extremely light and then the colony itself that?s being pulled by the sail would be just a tiny little speck compared with this enormous sail. It would glide serenely through space, lit up from time to time as the sail hit dust particles on the way.?
An interstellar ship would be like an ark, carrying everything the colonists might need, including greenhouses for growing food and sophisticated manufacturing facilities. Anthropologists think it could be important for the crew to be composed of a variety of nationalities to increase the size of the gene pool. And if these humans remained in reproductive isolation for long enough, they could evolve into another species altogether.
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The volunteers who went on a long mission would have to realize that they would probably not live to see the ship?s final destination. Linguistics expert Professor Sarah Thompson of the University of Michigan, believes the colony could soon have difficulties communicating with Earth. ?Let?s say you start with one language?perhaps English,? she says. ?After 500 years, English will have changed so much on Earth and so much, and completely independently, on the spaceship that they will be mutually unintelligible. So, you'll have space English and Earth English and they won?t be able to communicate.?
Basic vocabulary like mother, father, run, walk and sit would still be used but words that don?t apply to life in space, like car and train, would die out. Thompson thinks the most noticeable change will be the dialect they speak. She says, ?This single relatively homogeneous dialect will be noticeable with the first generation of children born on the space vehicle and will surely result in a dialect that differs from all of the parents? dialects, and from every other dialect of English spoken on Earth.?
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