It is quite amazing how, since the first DARPA/NASA interstellar voyaging conference was held (I was happy to be invited to the second conference, in Houston), awareness of exoplanets and the 'interstellar realm' in general have come in science and in the public imagination. I'm thrilled to be contributing in this research field, updating important estimates generated over a generation ago and with quite different overall paradigms regarding ''humans-in-space'', some of which I tackle in my popular-science title, "Emigrating Beyond Earth".
Smith, C.M. 2014. Estimation of a genetically viable population for multigenerational interstellar voyaging: Review and data for project Hyperion. Acta Astronautica Volume 97, April–May 2014, Pages 16–29.
Highlights • I review the literature on human populations for multigenerational interstellar travel. • I find previous estimates might be possible but are risky over multiple generations. • I suggest space voyaging populations on the order of 20,000–40,000. • Other figures can be proposed providing they are safe through multiple generations.
Designing interstellar starships for human migration to exoplanets requires establishing the starship population, which factors into many variables including closed-ecosystem design, architecture, mass and propulsion. I review the central issues of population genetics (effects of mutation, migration, selection and drift) for human populations on such voyages, specifically referencing a roughly 5-generation (c. 150-year) voyage currently in the realm of thought among Icarus Interstellar's Project Hyperion research group. I present several formulae as well as concrete numbers that can be used to help determine populations that could survive such journeys in good health. I find that previously proposed such populations, on the order of a few hundred individuals, are significantly too low to consider based on current understanding of vertebrate (including human) genetics and population dynamics. Population genetics theory, calculations and computer modeling determine that a properly screened and age- and sex-structured total founding population (Nc) of anywhere from roughly 14,000 to 44,000 people would be sufficient to survive such journeys in good health. A safe and well-considered Nc figure is 40,000, an Interstellar Migrant Population (IMP) composed of an Effective Population [Ne] of 23,400 reproductive males and females, the rest being pre- or post-reproductive individuals. This number would maintain good health over five generations despite (a) increased inbreeding resulting from a relatively small human population, (b) depressed genetic diversity due to the founder effect, (c) demographic change through time and (d) expectation of at least one severe population catastrophe over the 5-generation voyage.
Multigenerational space travel; Space genetics; Space colonization; Space settlement