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A visionary multi-billionaire wants to colonise the Universe with his Von Neumann probe printer to create a stunning variety of life and culture within our awe-inspiringly huge yet silent universe.

In order to do this a 3D-printing probe would be launched, travel for thousands of years, land on another planet, print itself (Von Neumann-style), and then spend the rest of the time printing life forms. The probe can happily keep printing any object of any size up to perhaps the size of a large tree (say a redwood), and can walk around the planet, and do so for millions of years.

So the question is: with the goal in mind of creating a high tech human society eventually, what is the absolute minimum list of species needed to create a thriving ecosystem for humans to survive on the surface (who would be printed last) of these planets?

Keep in mind the following:

  • Although the probe will land on every planet within reach (including ice giants etc), it is only necessary for the probe to create life on rocky planets roughly earth-sized with a light atmosphere with a temperature already similar to Earth.
  • The atmosphere may indeed be toxic initially, but over millions of years the probe by printing life can alter it
  • The probe has an unobtainium energy source that allows indefinite energy to print. It can print itself or biological life, but cannot print anything else - for millions of years (target perhaps 1 million years to accomplish its goal)
  • The probe can reconfigure matter it finds on a molecular level into a biological form (ie. nitrogen, carbon, hydrogen can be reconfigured to create any organic molecule)
  • The end-goal is a planet similar to earth prior to humans to survive - but does not need to include every species not necessary for this (ie. can skip dinosaurs, but may want chickens to eat).

Bonus points go to a list ordered in sequence of printing that achieves the result in as minimum time as possible.

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    $\begingroup$ Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Worldbuilding Meta, or in Worldbuilding Chat. Comments continuing discussion may be removed. $\endgroup$ Commented Aug 13, 2025 at 13:55
  • $\begingroup$ How freely can the printable species be designed? Part of your question of a working ecosystem hinges on a concept of reliance of one species on another (e.g. plants needing CO2 and providing O2, and animals needing O2 and providing CO2). But intelligent design of the species can significantly simplify that process. Are you trying to stick to an Earth-like ecosystem complexity/variety, or are you open to a significantly simpler version that only works based on intelligent printer designs? $\endgroup$ Commented Aug 14, 2025 at 1:17

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Note: It depends what ecosystem you're creating. A planet will have very many sub-ecosystems but some basic commonalities of interdependency.

The absolute minimum may well be down as low as half a dozen, if the colonists are prepared to eat basic yeast-algae based slop, but the greater the number of species, the greater the ultimate stability of a system.

Given time, creatures will evolve to fit niches in the world that are unpredictable. Again, the increased occurrence of this will promote the chances of resilience against extra-seasonal variations caused by eccentric orbits, freak weather, unexplained population collapse.

The species below represent a stab at a general ecosystem. The numbers represent the number of species. The number of genetically distinct individuals in each species would vary. The minimum viable population will vary greatly by species, some only needing hundreds, some many thousands. The fewer supplied, the greater the chances of the population suffering failure through lack of variability in the genome (and the physiological/behavioural and immune-responses of individuals).

The machine, being a quasi-omnipotent AI would need to constantly monitor the balance and make adjustments until the system showed signs of homeostasis without too many wild swings - and step in again if things needed adjusting.

First 1000 years:

  • Cyanobacteria. Initial oxygen production. (~10 species) The species number will increase as niches are colonized over time - allow for mutations and speciation at this stage.

  • Nanophytoplankton. (~10 species) Carbon fixation in oceans (chalk formation etc..)

  • Nitrogen fixers. Converts gaseous nitrogen to various salts available in the water-table. (~5 species)

1000 - 50,000/100,000 years:

  • Algae. Greater oxygen generation capacity, more biomass generated. (~5 species)

  • Fungi. Breaking down dead biomass. (~5 species)

100,000 year point:

Land:

  • Tough grasses. Soil stabilization and creation of humus in decomposing. (~5 species)

  • Flowering woody-shrubs, trees. Carbon fixation. (~10 species)

  • Fertilizing insects. Apis melifera (honeybee), bumble bees, ants, wasps. (~20 species)

  • Butterflies, moths. (Aesthetics, pollination.) (~20 species)

  • Worms - earthworms and various nematodes and flatworms (land and aquatic). Soil creation and improvement. (~30 species)

  • Mosses, lichens, ferns and Worts. Humus creation and spreading biomatter over inorganic substrates - paving the way for larger species. (Plus, they're laying down peat should the future need it.) (~20 species)

  • Slugs, snails. Turning organic matter into altered biomass, stimulating plant growth. (~10 species)

  • Flies. Dragonflies. Spiders. (~20 species)

  • Termites. Increase wood breakdown. (~5 species)

  • More fungi. Cellulose breakdown. (~5 species)

  • Tardigrades in the soil to deal with the tinyest fragments of cell-debris.

  • More bacterial strains (land/water): Rhizobium leguminosarum, Pseudomonas putida, Bacillus subtilis, Desulfovibrio desulfuricans, Actinomyces israelii, Bacteroides fragilis, Geobacillus stearothermophilus, Methanococcus (Methanocaldococcus) jannaschii - This list of 8 strains is provisional and I will update as I can. Given the timescales and bacterial reproduction/mutation rates, I would expect hundreds of thousands to millions of strains to be available around the 1 million year mark.

Sea:

  • Phytoplankton, small shrimps. Corals for more carbon-fixation. (~15 species)

  • Multicellular algae. (~5 species)

  • Kelp, sea-grasses. (~10 species)

  • (Aquatic) Slugs, snails. Turning organic matter into altered biomass, stimulating plant growth. (~10 species)

  • Echinoderms (urchin-family) and bivalves. (~10 species)

500,000 year mark:

Land:

Flora:

  • More flowering plants. Squash, legumes (nitrogen fixation by bacteria in root nodules) fruit trees, nut trees. (~20 species.)

  • More grasses. Maize, barley, wheat, oats, wetland grasses, reeds etc.. (~20 species)

Fauna:

  • Herbivores, mainly small grass-eating. Hares, rabbits, deer. (~5 species)

  • Carnivores. Foxes, eagles. (~5 species)

  • Omnivores. Small rodents - mice, voles, shrews. Chickens, pigeons. (~10 species)

  • Ophidians (snakes). As poisonous or not as you like, keep the rodent population down. (~10 species)

  • Beavers and amphibians. Wetland species will begin to thrive. (~5 species)

Sea:

  • Fish. Minnows, bream, bass, ray, tuna. (~10 species)

  • Shoreline. Muscles, limpets. (~5 species)

  • Larger shrimp, crabs, squid/octopus. (~5 species)

950,000 Year mark:

  • Caprinae (goats, sheep). Great for varied landscape and produce milk and meat. (~10 species)

  • Bison, wolves, camelids (as pack animals in various terrain), medium-sized cats. (~10 species)

  • Corvids for scavenging. (~5 species)

  • Sharks, eels, salmon, carp, catfish. (~5 species)

  • Cockroaches. (Yep.) (~5 species)

  • Small birds. Finches, tits, basket-weavers, songbirds. (~10 species)

To improve the livestock and ensure immune-fitness, a number of parasites (ecto and entero might be introduced). Mosquitos, horseflies. Bats would come in handy at this time. (~30 species)

  • Total: 419 species.

Note 2:

It may be necessary to reintroduce species that have fallen to over-predation and catastrophe - the perfect storm can ruin any plan, so corrective measures should be able to be taken. In an idealized scenario, the AI driving the terraforming would be able to compensate for minor changes to genomes such that any unexpected aberrations through mutation produced strange forms that threatened the stability of the whole.

There is also no reason not to include any species you fancy. For example, elephants are great clearers of new-growth and will devastate woodlands wherever the herds wonder, but maybe that's an effect you want.

I figure that a few alligators in the fresh water lakes/waterholes/rivers in equatorial regions wouldn't go amiss, but I leave that to the discretion of the worldbuilder.

Aquatic mammals tend to fit at the top of (or somewhat adjacent to) food chains and can be added at the discretion of the w/b during the latter stages, let the fish-stocks build up and stabilize first.

Note bee:

Honeybees don't have much by way of an immune-system of their own. The immunity that colonies have they gain from the various trees, shrubs and plants they visit, using Phyto-chemicals to ward-off infections and parasites. The greater the variety of trees and flowering plants, the more chance of bees flourishing and getting the job done.

1,000,000 years:

In real-life, Hominidae, the family containing us, produced the last common ancestor of chimpanzees and humans (Hominini) roughly 10 million years ago, having split and the ancestor disappearing perhaps 5 million years since. Lucy (Australopithecus) dates to around the 3.2 million year mark. Homo arriving on the scene around the 2.75 million year mark - in many varieties.

The "mitochondrial Eve" from whom all women descend is estimated to have lived 155, 000 years ago. Y chromosomal Adam (from whom all men inherit their Y chromosome) somewhere between 200,000 and 300,000 years ago - which roughly coincides with the advent of physiologically modern humans.

If you want humans to evolve, then you need a much longer plan. Alternatively, print them whole at some suitable point in their ancestry. We modern humans are thought to derive our existence from repeated mixing and separation, then mixing again between all the many, many separate lineages with each mix altering the genome and the creature you'd see.

You've a whole menagerie to chose from to create the finished product with at least 8 different distinct lineages of Homo going into our makeup in varying amounts at different times.

  • Additional Homo varieties: ~8. Possibly more variations by height, pigmentation etc..
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    $\begingroup$ Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Worldbuilding Meta, or in Worldbuilding Chat. Comments continuing discussion may be removed. $\endgroup$ Commented Aug 15, 2025 at 21:19
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I think the movie The Martian gave you a big hint.

You need:

  1. bacteria to make the ground into soil where plants can grow, nitrogen fixers among them
  2. algae and plants to produce oxygen,
  3. bacteria, worms and fungi to do the decomposition of the wastes

Once you have a cycle ensuring your humans can breathe, you can start adding the most relevant plants for human feeding: wheat, corn and rice with their pollinators and the livestock.

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    $\begingroup$ Worms! (That is not a comment about the userbase.) $\endgroup$ Commented Aug 12, 2025 at 7:55
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    $\begingroup$ @Escapeddentalpatient. Onceupona Timetherewere Somesmallworms Whogotveryvery Annoyedand Decidedto Gotoarmsin Ordertowipe Outtheir Viciousenemy Counterparts.... $\endgroup$ Commented yesterday
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There are many conditions that the Von Neumann machine will have to tackle. It may land on an inner planet with heavy minerals and little water. It may land on a water world with deep water and all the heavy elements have gone to the bottom. It may land on Mars with peroxides and bleach in the soil which would kill most earth-like lifeforms.

I imagine the Von Neumann machine can capture energy and materials from its environment and create complex structures at the atomic level. I imagine it uses carbon for its own internal circuitry which would also be handy for creating simple carbon-based lifeforms that are suited to the planet.

We do not know much about very early life on Earth. It is likely that the first forms that could reproduce themselves may have done by slowly gathering material from their environment, looking more like crystallisation than life as we currently know it. They may not have had a cell wall at all. We see fossilised remains of stromatolites, and possibly remains of early bacteria. It is quite possible that the original first thing that could copy itself was something quite different, and that was completely lost when more complex life forms preyed on it. People have suggested structures in early clays may have been a sheet-like silicate proto-lifeform which reproduced by peeling off layers.

The first step to creating life might then be to create some simple photo-lifeform tailored to suit the ambient chemistry. This would make copies of itself, and also concentrate resources in one place. Once you had a good starting point, it might then jump to something like stromatolites. It is not just making copies of Earth species and setting them loose, but making something suited to the environment. However, it could proceed much more rapidly than evolution as it could add cell walls, photosynthesis, flagella, multicellular forms, and so on without waiting for them to occur by chance.

It would probably take millions of years to affect the whole planet starting from one point no matter how clever the machine was. We know a few cases where a life form has changed the atmosphere. Trees took carbon dioxide out of the atmosphere in the carboniferous period. The Azolla Event may have ended the Eocene in just under a million years. We are doing serious things right now, but it took a long while for us to get started.

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  • $\begingroup$ Didn't know about the Azolla event. Turns out it's a sort of fern. Totally agree about timescale being unrealistic. $\endgroup$ Commented Aug 13, 2025 at 18:06
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    $\begingroup$ @Escapeddentalpatient. It may be possible to speed things up a bit of the Von Neumann machine could make lots of other copies of itself, so what it does would be more like farming. It might be possible to make artificial life that fixed carbon from atmospheric carbon dioxide much faster than the plants of the carboniferous, or anything that evolved to fill a niche. If the story required it, we could probably remove an order of magnitude. $\endgroup$ Commented Aug 13, 2025 at 19:43

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