To start a genetically diverse, self‑sustaining colony on another planet you need at least a few hundred people for a very “bare minimum” scenario , but realistic, safer designs usually aim for several thousand to tens of thousands , depending on trip length, technology, and how conservative you want to be about genetic health and social stability.

Quick numerical ranges

Different studies and experts give different numbers because they assume different conditions:

  • ~110 people : One mathematical model focused only on survival on Mars (not on long interstellar travel) found that, with a well‑organized society and strong sharing of tasks, you could get long‑term survival with about 110 settlers. This is more about labor and time requirements than genetic diversity.
  • ~160 people : An older study for a 200‑year space journey (roughly 8–10 generations) suggested about 160 people as the minimum to keep genetic variety stable, giving roughly 10 potential partners per person.
  • ~100–1,000 people : Forum discussions and some analyses argue that, if you can only send living humans, a bare minimum gene pool is around 100 people, but you’d ideally want up to 1,000 if your ship and mission can support it.
  • ~14,000–44,000 people : For a 150‑year interstellar voyage, anthropologist Cameron Smith modeled that a founding population of 14,000–44,000 would maintain good health over five generations and avoid an extinction vortex; he recommends about 40,000 as a “safe and well‑considered figure” (roughly 23,000 of reproductive age).
  • ~50–500 people (rule of thumb) : The so‑called “50/500 rule” in conservation biology says:
    • At least 50 individuals to avoid immediate inbreeding problems.
    • At least 500 to reduce long‑term genetic drift and maintain diversity.

These are not exact “laws” but guides used by biologists and population geneticists.

Why the numbers vary so much

The answer depends on several key variables:

  1. Trip length / number of generations
    • A short trip (decades, 1–2 generations) can tolerate much smaller groups.
    • A 150–1,000 year trip (many generations) needs far more people to avoid inbreeding and loss of diversity over time.
  1. Genetic diversity goals
    • “Just avoid obvious inbreeding” vs. “maintain full human genetic diversity like Earth” are very different targets.
    • Higher diversity requirements push the number into the thousands.
  1. Technology and buffers
    • If you can carry cryopreserved sperm/egg banks and have advanced medical genetics, you can reduce the living population needed.
    • If you rely only on the living crew, you need more people to cover the same genetic base.
  1. Social and economic complexity
    • A colony that wants to be fully self‑sufficient (medicine, engineering, agriculture, manufacturing, education, governance) needs many specialized roles.
    • More roles → more people. Smith argues that large populations give you the “extreme specialization” needed for true self‑sufficiency.
  1. Risk tolerance
    • “Bare minimum to squeak by” vs. “good margin for disaster” are opposite philosophies.
    • Conservative designs (extra safety against accidents, disease, social conflict) push numbers up dramatically.

How this looks for different scenarios

1. Mars or nearby planet (short trip, Earth backup possible)

  • Minimal viable group : ~110–200 people, if you:
    • Organize society very efficiently,
    • Share tasks heavily,
    • Accept some loss of long‑term genetic diversity,
    • And assume you can still call on Earth for help or resupply.
  • More realistic “decent colony” : 1,000–5,000 people to:
    • Cover many specialties,
    • Reduce inbreeding risk over many generations,
    • Build a more resilient social and economic system.

2. Interstellar colony (no Earth backup, centuries of travel)

  • Very conservative, long‑term healthy colony : ~20,000–40,000 people, as modeled for a 150‑year voyage.
  • Optimistic “minimum that might work” : ~1,000–5,000 if:
    • You use advanced genetic management,
    • You accept some loss of diversity,
    • And you’re okay with higher risk of long‑term health and social problems.

3. “Just don’t inbreed quickly” (very short horizon)

If the question is only “how many to avoid obvious cousin‑marriage in the first few generations”:

  • The 50/500 rule suggests at least 50 people to avoid immediate inbreeding, but 500 to maintain diversity over time.
  • For a 1,000‑year trip (≈33 generations), a simple calculation suggests you’d need at least ~66 distinct partners (33 men + 33 women) just to avoid all cousin relationships in the first few generations, but that’s far too small for long‑term viability.

Bulleted takeaways

  • Absolute bare minimum for genetic viability : around 50–100 people, but this is risky and not sustainable over many generations.
  • More comfortable minimum : 160–1,000 people, depending on how much diversity you want to preserve and how long the mission lasts.
  • Safer, robust interstellar colony : 20,000–40,000 people to maintain health and diversity over multiple generations and handle disasters.
  • Mars‑style, short‑trip colony : 110–2,000 can work if you’re very efficient and accept some genetic limitations.

Final concise answer

If you want a truly genetically diverse, resilient, self‑sustaining human colony on another planet, especially with no Earth backup and long travel times, most serious models suggest tens of thousands of people (around 20,000–40,000).

If you’re asking for the absolute theoretical minimum just to avoid immediate inbreeding and get a small colony started, you can get into the low hundreds (roughly 100–200), but with significant long‑term genetic and social risks.

Information gathered from public forums or data available on the internet and portrayed here.