Saturday, September 7, 2013

Interstellar Migration Population paper; Edits and Revamp

After mind-melting experiences in Copenhagen I needed to change channels for a little while. I spent the last week reviewing and revamping my paper on the genetics of multigenerational interstellar voyaging. Humanity isn't ready to do this, but that's fine, it will take a long time to get ready. This is part of my effort in Icarus Interstellar's Project Hyperion, an international team laying the groundwork for a 100-year study of the physics of interstellar flight for human populations; the idea is to provide humanity with the physics and propulsion needed to make such voyages, if we want to do so, 100 years from now...pretty 'out there' stuff! I'll present this paper at a NASA-DARPA conference in Houston later this year. Abstract below. I think it;s ready for publication and am now massaging it for submission to Acta Astronautica;

Estimation of a Genetically and Demographically Viable Founding Population for Multigenerational Interstellar Voyaging

Cameron M. Smith
Department of Anthropology
Portland State University
August 2013
9,237 words, discounting references


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) and demographics (population size, age, and sex structure on departure) for human populations on such voyages, specifically referencing a roughly 5-generation (c.150-year) voyage currently in the realm of thought among the Icarus Interstellar 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 multigenerational voyage 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 ‘IMP’ or interstellar migrant population 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 and isolated 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.

4 comments: said...

Nice study. In my Sci/Fi novel I've done some similar research, (100 years/ 25,000 pax).

Anonymous said...

Hi Cameron,

Interesting problem you describe here. I assume that the population you suggest, randomly can choose their partner, with whom to produce next generation.
Then I'm curious for knowing: What is the absolute minimal population required if mating is planned and controlled.
This must be similar to problems faced by ZOO's trying to grow populations of close-to-extincted animals.

Best regards

Cameron McPherson Smith said...

Thanks, guys. An absolutely minimum population for a multigenerational voyage might be in the low 000's. However, going on such a project with the minimum possible puts you at severe risk of demographic collapse; a plague does not have to kill everyone outright to kill you off; it just needs to upset the demographic structure, e.g. finding mates of appropriate age / sex, to put you into an 'extinction vortex' (a term from conservation biology). So in this paper I recommend doubling or tripling or more a genetically viable population of about 10,000 for a total of 20-40k people. If this voyage will be generations in duration it would be wise to go in larger numbers, even though the 'startup costs' will be higher. A larger population is your insurance policy. One could 'wing it' with smaller figures, but they would always have the spectre of collapse on their heels. I will post the link to the full article when it's published. I would be thrilled to read your accounts / novels. Many have written fiction on this topic, but I'm just starting into the real-world genetics. A population of 40k is not so bad if you break it into modules, e.g. eight 'cities' of 5000 each, etc. Cheers Cameron

Cameron McPherson Smith said...

More issues regarding this topic can be found below:

My podcast at Scientific American:

(you can safely ignore the comments on that page!)

My article in Scientific American:


Anotehr article, this time at Paul Gilster's 'Centaur Dreams' site:

And in my book:

I am writing further on this topic at present and will have more articles in the peer-reviewed as well as popular literature in the next few years.