The "magic number" of people needed to create a viable population for multi-generational space travel has been calculated by researchers. It is about the size of a small village - 160. But with some social engineering it might even be possible to halve this to 80.
Anthropologist John Moore from
University of Florida tackled the problem as part of a combined effort
with space scientists to determine how in future humans might
successfully undertake century-long journeys out into space.
In the past, attention has been
focused on cryogenics, sperm banks and military-style modes of
operation, says Moore, but "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 - for analysing the viability of small
groups.
Marriage partners
For a space trip of 200 years, perhaps
eight to 10 generations, 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 a small
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 strategies. The first is to begin with
young childless couples, echoing the practice of Polynesian seafaring
colonists.
The second is to ask the space crew to
postpone reproduction to later in woman's fertile period, perhaps age
35 to 40, creating longer time gaps between the generations. This
measure results in a stable population of just 80 but the consequences
of the increased medical risks of late childbirth have not yet been
considered.
A potential concern is that small
populations can suffer a damaging reduction in genetic diversity due to
inbreeding, says Dennis O'Rourke from the University of Utah. He
considered the same 10-generation, 200-year journey as Moore and looked
at both genetic drift and inbreeding.
"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 travellers come home or interact with other humans at
the end of the 200 year period."
Gene screening
O'Rourke believes that a more serious
concern would be the presence of potentially damaging genotypes in the
initial space pioneers. Genetic screening might well be needed, he says:
"Any harmful recessive characteristics might lead to increased
healthcare loads which would deplete scarce resources."
A final concern raised at the American
Association for the Advancement of Science's annual meeting in Boston
was the possibility of infighting. Small communities isolated for long
periods at research stations in Antarctic and even families travelling
on long car journeys, provide examples of how small conflicts can
quickly escalate.
But Moore points out: "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 are not taken to Antarctica."
Via newscientist.com
Via newscientist.com
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