I am trying to increase the diversity of beings in this sci-if futuristic project, and am considering the use of pantropy to do so. Pantropy means genetically altering humans to inhabit unfamiliar planetary environments, rather than terraforming, which involves changing the planets to suit the humans.

However, I have put a lot of work into imaging methods of terraforming other planets, many of which I have already integrated into this project. If I keep them, then this means that people will be terraforming some planets and adapting colonists for others. But why would we do this? Why would terraforming and pantropy coexist in the same setting?

(A note on answering: please don’t give a list of reasons why terraforming is costly or pantropy unethical to explain why the other is a better idea; I am looking for ideas as to why both should be used, not one over the other.

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    $\begingroup$ VTC: Brainstorming, Storybuilding, All answers have equal value, open-ended, opinion-based. See help center. $\endgroup$
    – JBH
    Commented Dec 17, 2022 at 22:08
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    $\begingroup$ Why do you think having both is incompatible? different solutions for different problems. $\endgroup$
    – John
    Commented Dec 18, 2022 at 0:08
  • $\begingroup$ @John Stack exchange isn't designed for popularity contests where a question can have many equally valid answers. That's every SE site prohibits such questions. It's in the boilerplate policy for every site on the network. $\endgroup$
    – sphennings
    Commented Dec 18, 2022 at 0:24
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    $\begingroup$ @sphennings John might have been referring to the question and not my comment. $\endgroup$
    – JBH
    Commented Dec 18, 2022 at 3:13
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    $\begingroup$ Uh… how could it be problematic for both genetically modified humans and terraforming to exist? $\endgroup$ Commented Dec 19, 2022 at 1:54

17 Answers 17


Different goals


Pantropy requires much less resources. You just modify a set of people who are going to live on that one colony, and they will procreate and thus generate new people to work there.

But it's also rather limited. Since you are editing genes, that means it would be really hard to modify an already-born person. In vitro gene modification is much easier, cheaper and way more effective.

So if you modify some people to live in really hot climates, they probably won't work well in temperate climates.

A pantrope is more or less limited to their world.


Terraforming is a really expensive process. You literally have to transform a whole planet for it to be worthwhile.

But the outcome means that the unmodified "standard" humans can live there.


Pantropy is for the low-class workers on low-importance colonies. These will be your farmers, miners, ..., who do dangerous resource extraction on otherwise unimportant planets. These planets might feature smaller biospheres for the standard humans who are managing the colonies.

Terraforming is for the upper-class planets with regional or super regional importance. This is where your upper-class standard humans live and rule the galaxy from.

When I say "standard humans", that doesn't necessarily mean they are unmodified. But they are made for living in the galactic standard living circumstances: moderate temperature, moderate humidity, 1G gravity, non-toxic food with normal nutritional values and such.

The pantropes on the other hand are specialized for a specific habitat.

Depending on the topics you want to touch on, this also gives you the foundation for some discrimination/class conflict/race conflict themes in your story.

For comparison look at the belters in The Expanse. They are pretty much that, though not created on purpose.

  • Pantropy during the early stages of terraforming, then it just sticks.
    Say you have a world that should be shirtsleeve-habitable for unmodified humans in just, oh, three or four centuries. So the colonists alter their offspring to meet the terraforming project halfway. A modified colonist will be able to survive outside in a century or so. Much better for their mental health that they could go out, in case a seal breaks. And by the time a baseline human could survive outside, will the colonists change back? That's assuming the pantropic mods can survive in earthlike environments.
    (Various writers have expounded on how supposedly the first generation builds things, the second maintains them, and the third lets maintenance slide. So it is a bad idea to rely on domed cities for centuries.)

  • Terraformed worlds can be visited by everybody.
    That's assuming space travel is reasonably easy. Once you go through the effort and time of terraforming, you can attract visitors and immigrants without multi-generation schemes to alter their offspring.
    An artist could come for a tour, a scientist could come for a conference, and so on. That means you can attract top talent to your world.


History is a hodgepodge of historical events

World 'A' was terraformed by a rich organisation who valued their default human bodies and had the resources to terraform it. In addition this particular world was well suited to terraforming, which is why they chose it.

World 'B', a waterworld, is inhabited by fish people, all descended from a group of refugees from a war, who were desperate for somewhere to live and had the technology to transform their genetics. The rich 'default human' inhabitants of world 'A' would quite like to terraform world 'B', but they can't, because the fish people live there.

World 'C' wasn't always a waterworld, but it is now, having been terraformed by the inhabitants of world 'B', who having lived as fish people for thousands of years have come to rather like it.

And so it goes on. As worldbuilder you get to choose the history of each world individually, and the choice of terraforming versus pantropy could easily be different for each world. Presumably terraforming will usually only be used on uninhabited worlds, and presumably some worlds will be better suited for terraforming than others, so there is a lot of scope for the decision to go different ways in different cases.


Alleviate the effects of law of diminishing returns, speed up the process

If you need one of them, as the question implies, it can be better if you do both. You aim at a (so-far unknown) sweet spot where the terraformed environment and engineered humans are as compatible as possible because it optimizes the process.

Terraforming is an enormous project, and the further you want to take it, the more it eats up resources. Due to the law of diminishing returns, the last 20 % might consume resources as much as the first 80 %, for example.

See https://en.wikipedia.org/wiki/Diminishing_returns

Engineering humans to adapt to a non-terraformed environment, on the other hand, is error-prone due the sheer complexity of any biological organism. You don't want to take it too far because you don't really know if the engineered humans function as intended: need for genetic engineering at this time strongly implies that the required genetic solution is not yet known. Therefore, you do small adaptations at a time; they are safer and easier. Law of diminishing returns also apply here.

So, it could be more reasonable to start terraforming and genetic engineering at the same time, and work up iteratively until desired level of compatibility has been achieved. That is the sweet spot where investment in time and resources is more or less as small as possible.


Comparative Advantage of the Methods

For some parts of adapting a human to a new environment it is just cheaper to alter the human or the environment respectively. Thus, simple economics creates an adaptive mish mash. For example, it is hard to supply a human brain with energy. That is why you build an oxygen atmosphere and bioreactors to produce food. But that the same time you tweak the digestive system. On another note, adjusting gravity is hard. But adopting humans for zero or low gravity is rather trivial.

Because People Want It

In settings like The Culture or Orion's Arm Automation is so advanced that economic limitations are rather inconsequential. In this case groups might just prefer one way or the other. Different groups might consider either adaptation style artistically valuable.

  • $\begingroup$ Another example - Hyperion Cantos. There was a group of people who went out into space first, adjusting their bodies because this was simpler and more in harmony with the nature of the cosmos, and they accepted the risks, and then the terraformers who only started to colonize when economy and technology advanced enough. $\endgroup$
    – Mołot
    Commented Dec 20, 2022 at 0:39

Life only works in a narrow band

Is your planet's ambient temperature above the boiling point of water? No amount of genetic engineering is likely to make a creature (beyond some extremophile bacteria) that can live in that. Is there no oxygen? Nothing resembling a human could survive until you fix that.

Most planets will require terraforming. (With the exception of Earth, every celestial body we've had a good look at would not support anything even vaguely like humans.)

Humans are optimized for conditions we may not be able to exactly duplicate.

If your planet receives half the light that Earth does, it might be easier to engineer more sensitive eyes (and less sensitivity to light-based mood disorders?) than to make the local star brighter, or to drag the planet closer to the star, or to set up orbital mirrors to make things brighter...

Terraforming and pantropy are not mutually exclusive ways to address colonizing other worlds.


Scary Sensitive Aliens

The baddy alien empire is out to get us! The aliens like the same atmosphere and gravity as baseline humans do. And they cannot or will not do genetic engineering to their people. That is why we engineer ourselves to live where the aliens cannot. Invading our home worlds is difficult when every invader needs a space suit not to suffocate, melt, and collapse all at once.



One interest conducts colonization using pantropy. Another terraforms worlds and drops in unmodified humans. These interests are competitive and collect returns on their investments in planets and humans. Within these two general camps are subgroups: terraformers using brute force to wipe a world clean and more delicate terraformers making precise alterations. Pantropists who tweak the human genome and pantropists who are making frank human - nonhuman hybrids.

There are other schools of thought as regards colonization. Tech centered colonization uses basic humans (or modified humans; whatever is available) and unmodified worlds and leverages technology to allow human existence on these alien worlds. There are a few worlds colonized by wholly artificial / synthetic beings.

Once you have invested in an successful approach it makes more sense to improve your methods than to jettison them and start fresh.


It's considered illegal/unethical to terraform a world with native life

Suppose an interstellar colony ship reaches a planet which is not a "shirtsleeves" habitable environment to humans, but has its own native life. The planet is close enough to Earth that it could be terraformed relatively easily, but changing the environment from one that's lethal to Terran lifeforms to one that's hospitable to them would do the reverse for the native life, leading to an extinction level event, and unique life forms being lost forever.

Having seen enough native Terran species wiped out in the 20th and 21st century, humans are all too aware of the damage they can do to existing ecosystems. There's also the potential that any world with any native life at all could one day evolve a new sentient species, and wiping out any existing species could prevent that happening.

For that reason, settling humans on a planet with native life is, while not illegal, a minefield of issues the settlers must be aware of. One of those is to refrain from certain avoidable changes to the environment, the most pronounced of which is an absolute ban on any form of terraforming. Some limited form of paraterraforming might be permissible if the location being paraterraformed is somewhere isolated with no native life to displace (eg a mountain top), but otherwise settlers must either remain inside the colony, or adapt themselves to fit the environment. A standardised audit for native life, conducted by an independent observer, is an absolute requirement for any world that could potentially host life before the first colonist even lands, and that establishes what measures must be taken in that case. Any colony that broke these rules would find themselves in very serious legal trouble, with potential punishments including:

  • The colony being broken up and the colonists evacuated
  • The personnel directly responsible facing charges of crimes against humanity in a court of law
  • The organization sponsoring the colony facing an extremely substantial fine, in addition to the complete loss of all investment in the new colony, in addition to damage to their reputation, making it unlikely partners and colonists will be willing to take part in future projects

On less-habitable worlds where no native life exists to displace, no such restrictions apply. A shorter, simpler audit to establish that the world doesn't host life is generally sufficient. Colonists are free to crash comets into the surface to thicken the atmosphere, introduce algae to convert CO2 to oxygen, and so on, safe in the knowledge that no native life exists to displace.



Political party T supports Terraforming while political party P supports Pantropy. Humans are a naturally divisive species and the media loves framing things as an us vs them. As such some people go around terraforming planets while some people are investing in pantropy. They are each convinced their approach is the superior approach regardless of what the other group says.

Businesses heavily invested in genetics would be incline to support Party P while businesses heavily invested in terraforming would be incline to support Party T. This would result in lots of money being funneled through various channels into each party propping up legislation that is pro terraforming or pro pantropy. This could get rather ugly and nasty, and much like how there used to be Protestant vs Catholic countries in Europe similar could arise in this future setting but instead it is Pantropy vs Terraforming countries.

The end result is some planets are terraformed while other people are adapted to survive in them. There can be also be moderates who try to compromise and do a bit of both.


On a single world? People want to take their dogs and cats: those animals need terraforming if they’re going to be the same dogs and cats we love. People who can redesign their kids’ genetics will have all sorts of fashion, supply-chain, and cultural pressures that push both for diversity and purification at different times. Gills may be in fashion, especially on a water-common world. Multiple arms could be useful. Bring back the prehensile tail! Lots of useful body-mods for functionality and fashion exist even within Earth-normal parameters.

Across many worlds, this should obvious: the galaxy is big, cultural homogeneity is unlikely. Some worlds will push toward standard humans and some will push away, with all the usual reasons for humans to do anything.

  1. Even on an ideally terraformed planet, as-is humans cannot fill all niches, for example on Earth humans are basically absent at the poles and barely present in the oceans. If your planet has some good resources in those areas then it makes sense to put people there.

  2. Excessive and/or fast terraforming will destroy the resource you're trying to get. Say you find a planet that has some plant/animal which produces the most wonderful perfume or foodstuff or other luxury item. If you alter the planet then you'll kill off your resource. Even if you try to modify the resource to grow in other environments that's going to be slow to figure out this new plant/animal and you want it now. You already know about adapting humans so do that instead.


Why do footwear (mechanically modified humans) and sidewalks both exist?

Modified humans would be used in places where that process is too expensive (replacing an entire atmosphere), or where the modification is actually desirable (we can fly!).

Terraforming would be used for places that don't need much effort to improve, that could be used for high population densities, that are desirable destinations. If the shoe fits, they wear it.


There are some very good answers here already, I would just like to add some more.

Here are some examples why I think they could co-exist:

Reasons for Pantropy to exist:

  1. Planet core is already solid and therefore no magnetic protection from radiation.

  2. Sun / Starlight that reaches the planet is of a specific colour / wavelength that is not ideal for original species.

  3. gravity of said planet is too high / too low to sustain the current size of species.

Reasons for Teraforming:

  1. not wanting to make too many differences in the species which can eventally lead to a different enough species which then would become their own species and in case of central government, want to be sovreign and self governing.

  2. use of already established ways (legacy technology) of doing the following for example:

    • Generating energy (i.e. rivers, wind geo etc. (assuming that they are not using fusion yet)

    • Agriculture

    • Animal husbandry (I am assuming they are still being used as food source which sounds weird when you consider that this race is advanced enough to terraform and geneticly modify itself)


Contingency Planning for the Known & Unknown

Octavia Butler's Xenogenesis series (Dawn, Adulthood Rites, Imago) offers a deep-dive into this debate, casting both terraforming and pantropy as contingency solutions for long-term survival - of the species, not necessarily any subgroup.

The story focuses a lot on balancing survivability, agency, and adaptability, with the humans and their alien rescuers/invaders differing [sometimes violently!] on the relative priorities of each.

At any encounter with a new world, three groups are formed:

  • Planet-side terraformers, with the goal of reshaping the new world to better meet existing, known needs (max survivability)
  • Space-based explorers, who will remain unchanged on their ships, and continue traveling after major resupply (max agency)
  • Evolutionary cohort, modified to not only thrive in their terraformed "homeworld", but also ultimately leave for worlds unknown (max adaptability)

Essentially having both tools (plus the "neither" stay-in-space option) covers multiple contingencies, and avoids putting all the species' eggs in one easily-destroyed basket.


Your worldbuilding is more serious than George Lucas's

Don't get me wrong, I like Star Wars as much as the next nerd. But it's got a lot of horrible scifi in it, to the point that sometimes I don't want to watch it, nor even show it to my kid.

One of the things that I hate about it is how every planet has a single biome. Every place in that universe is either a planetary snowball, desert ball, jungle ball etc. but without any good reason.

If you are being serious about your work, then a planet that has been terraformed for humans will have multiple biomes, because it will have different latitudes (unless you're building something that would not qualify as a planet). It will necessarily have water bodies that are separate from land masses, and different wind and water current patterns in different places.

With a range of different biomes in a single planet, humanity may be able to colonize the whole of it by using technology - but some people will adapt to some environment more easily due to their genetic modifications. For example, people with whale-derived physiology will be much more comfortable at the bottom of the ocean than people who need a giant suppository just to not die there.

People with hands at the end of every limb and a prehensile tail could move more nimbly among both trees and skyscrapers. People who can see infrared would do better in very dark areas, etc. You can be as creative as you want there.

You can even take it up a notch and terraform the planet for the modified humans, and see how a non-modified human deals with it. There is this book I love, The Left Hand of Darkness, and while the planet in it is not terraformed, it is home to a variety of humans who have adapted to its cold environment. It practically never goes above freezing temperature, even at the lower latitudes. The protagonist is a regular human who is an alien in that world, and the poor guy has a very hard time dealing with the constant cold while the people of that planet are just fine. In one scene, the protagonist and the deuteragonist have to share a small tent, and the heating becomes a problem - whatever is comfortable for one of them, is terribly bad for the other. I can imagine many similar situations between modified and non-modified humans in places that have been artificially adapted to one but not the other.


Pantropy during the early stages of terraforming, then it just sticks.

"As of 1 December 2022, there are 5,284 confirmed exoplanets in 3,899 planetary systems, with 847 systems having more than one planet."

Presumably humans would start colonizing "first-generation" worlds that are both relatively nearby (relatively easy to travel to) and easy to transform (and not already filled with alien species). Once those are occupied (by Earthlings or alien species), humans would start colonizing worlds that are more distant or more difficult to transform or both.

As o.m. suggested,

Say you have a world that should be shirtsleeve-habitable for unmodified humans in just, oh, three or four centuries. So the colonists alter their offspring to meet the terraforming project halfway. A modified colonist will be able to survive outside in a century or so. Much better for their mental health that they could go out, in case a seal breaks. And by the time a baseline human could survive outside, will the colonists change back? (Various writers have expounded on how supposedly the first generation builds things, the second maintains them, and the third lets maintenance slide. So it is a bad idea to rely on domed cities for centuries.)

Let us assume that most planetary-mass objects under consideration for terraforming are on a linear spectrum of high-gravity world, therefore dense atmosphere, therefore high oxygen on one end, vs. low-gravity, therefore low oxygen at the other end, with Earth at 21% oxygen somewhere in the middle. (I feel this is plausible enough and useful for plot reasons, although there are likely many other variables that can't be condensed down into a single linear spectrum).

Assuming space travel is reasonably easy (especially if the more extremely modified colonists can't survive in conditions that are shirtsleeve-habitable for unmodified humans), after the first "generation" of worlds are completely terraformed (or perhaps 50% terraformed), and colonists begin to be selected to send to the second "generation" of worlds to be terraformed, it seems likely that second-generation low-oxygen worlds will have more volunteers from low-oxygen first-generation worlds, and second-generation high-oxygen worlds will have more volunteers from high-oxygen first-generation worlds.

Even if space travel is difficult, the genetic engineering will probably be easier / more successful starting from the descendants of already-modified colonists and making smaller tweaks, rather than starting from scratch from baseline humans every time.

If space travel is very easy, some colonists modified to thrive in, say, 15% oxygen levels may decide to travel for the first half of their lifespan, helping terraform even lower-oxygen planets (where they only need the equivalent of scuba gear to work outside, rather than the bulky spacesuits required by baseline humans or colonists modified to thrive at 50% oxygen), then later "retire" on some currently-near-15% oxygen world that is shirtsleeve-habitable to them (or will reach 15% oxygen / shirtsleeve-habitable in a few years).

After a few "terraforming generations" (likely each one several human generations), there will be a spectrum of modified humans.

Also, at any one time there will be a spectrum of worlds inhabited by human descendents:

  • worlds slightly past the ends of the spectrum of "shirtsleeve-habitable" by any human descendent that are being actively terraformed to bring into the modified-colonist range;
  • worlds that are technically inside that spectrum, but are still being actively terraformed because it is still "relatively easy" and would allow a greater variety of plants and animals to grow;
  • worlds that for a variety of reasons are not currently actively being terraformed, but are currently inside that spectrum (possibly because of terraforming activity in the past that was halted before it became habitable by baseline humans).

(this builds on o.m.'s answer).


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