Population modification

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This article is for the PC version of Stellaris only.
Every species can be radically changed through genetic or cybernetic modification
See also: Traits

Population modification refers to the process of altering a population's traits either to change its habitability, create subspecies suited for different tasks or improving it after unlocking more trait points through research. Both organic and robotic pops can be modified and each has its own set of traits. In addition, a small number of events can modify the population of a colony.

Species types

Species types define the trait types a species can have, the type of possible population modification, the way they unlock additional Trait Points and how their rights are determined.

Type Required Trait Modification type Initial Trait Points Rights
Biological None Genetic modification 2 Determined by Species Rights
Robotic Trait mechanical.png Mechanical Robomodding 0 Determined by Artificial Intelligence Policy
Machine Auth machine intelligence.png Machine Robomodding 1 Determined by Species Rights
Pre-sapient Trait uplifted.png Any pre-sapient trait Uplifting 1 Determined by Pre-Sapients Policy

Trait points and Picks

The two primary limiters to how many traits in what combination one can have are the Trait Points and Trait Picks. The first Contact with both is during on species creation screen. Various technologies add additional Trait Points but Trait Picks are always capped at 5. In Utopia traits given by ascension paths do not count towards either limit.

Species templates

The genetic modification menu.

Population modification is done via templates. Templates can be applied to pops residing on a planet or to the entire species, previously modified or not. Modified pops are considered part of the same species as the original even if the name and portraits have been changed. As such any change to the species rights of a template will be applied to the entire species, not just the template.

Templates with zero current pops can be freely modified or deleted however the ones with at least one pop cannot be changed and the template modification window presents only the option to create a new one.

After a template has been applied a special project to start modifying the selected pops will appear in the situation log. The project will timeout in 30 days if not started. Depending on the kind of modification, how severe the modification (total amount of trait point differences) and how many pops were picked, this special project can be very expensive in science. The system is currently designed towards favoring bulk modification of many traits over specific via a high base cost.

Type Genetic Modification Robomodding
Unlocked by Tech gene tailoring.png Gene Tailoring for traits
Tech glandular acclimation.png Glandular Acclimation for climate preference
Tech robomodding.png Machine Template System
  • 3000 Society Research Society Research
  • +5 per affected Pop
  • +20 per affected Pop per Trait Point Difference between the old and new Templates
  • +60 per affected Pop if climate preference is changed
  • -25% for Ap engineered evolution.png Engineered Evolution ascension perk
  • -25% for Ap evolutionary mastery.png Evolutionary Mastery ascension perk
  • 1500 Engineering Research Engineering Research
  • +20 per affected Pop
  • +40 per affected Pop per Trait Point Difference between the old and new Templates
  • -33% for Ap synthetic age.png Synthetic Age ascension perk
  • -50% for Ap synthetic evolution.png Synthetic Evolution ascension perk
Trait Points
  • Tech gene tailoring.png Gene Tailoring technology grants +1
  • Tech gene expressions.png Targeted Gene Expressions technology grants +1
  • Ap engineered evolution.png Engineered Evolution ascension perk grants +3
  • Ap evolutionary mastery.png Evolutionary Mastery ascension perk grants +3
  • Ap xeno compatibility.png Hybrid species have one additional trait point and one additional trait pick
  • Tech robomodding points 1.png Cross-Model Standardization / Binary Motivators technology grants +1
  • Tech robomodding points 2.png Fungible Circuitry / Nanite Assemblers technology grants +1
  • Tech robomodding.png Machine Template System technology grants +2
  • Tradition versatility adaptive programming.png Adaptive Programming Versatility tradition grants +1
  • Ap synthetic evolution.png Synthetic Evolution ascension perk grants +1
  • Ap synthetic age.png Synthetic Age ascension perk grants +2

The Biological Ascension path focuses entirely on genetic modification, granting new trait points, cheaper genetic modification and access to Tech genetic resequencing.png Genetic Resequencing technology, which gives the ability to rewrite ALL traits and allows access to Advanced Traits.


Uplifting is the process of turning a pre-sapient species into a fully sentient species. Uplifting a species has some advantages over conquering another species or other forms of genetic engineering.


  • Uplifting requires the Tech epigenetic triggers.png Epigenetic Triggers technology, and costs 5000 Society Research Society research.
  • Upon completion, the uplifted species is immediately integrated into the empire which uplifted it, and the homeworld is added to the empire as a free colony. Additionally, it will generate a large amount of Influence.
  • All uplifted species have a special trait that cannot be acquired during Empire creation or genetic modification. This trait will make them excel at some jobs far beyond what normal species can do, but often at the downside of making it unsuitable for other purposes.
  • The species will naturally be thankful to the species that uplifted them and get +10% Mod pop happiness.png happiness via the free Trait uplifted.png Uplifted Trait if staying in the same empire as their benefactors.
  • The species will appear with Random Ethics. Several prompts give the uplifting Empire an opportunity to help decide the species' ethics to override the original setting for all pops. The species is fully susceptible to Ethics divergence.


This special Citizenship with associated Living Standards allows the conversion of pops to better fit the existing empire, without the hassle of regular modification. Each year up to 4 pops will be assimilated: 1 pop (50%), 2 pops (30%), 4 pops (20%).

Assimilation type Requirements Trait changes
Ap evolutionary mastery.png Hive Dissociation Ap evolutionary mastery.png Evolutionary Mastery
Not Auth hive mind.png Hive Mind
Remove Hive-minded.png Hive-Minded
Hive-minded.png Identity Sublimation Ap evolutionary mastery.png Evolutionary Mastery
Auth hive mind.png Hive Mind
Add Hive-minded.png Hive-Minded
Trait cybernetic.png Identity Sublimation Civic machine assimilator.png Driven Assimilator Add Trait cybernetic.png Cybernetic
Remove Hive-minded.png Hive-Minded
Trait cybernetic.png Transubstantiation Synthesis Ap the flesh is weak.png The Flesh is Weak Add Trait cybernetic.png Cybernetic
Remove Hive-minded.png Hive-Minded
Trait robotic 3.png Transubstantiation Synthesis Ap synthetic evolution.png Synthetic Evolution Replace pop with Trait robotic 3.png Synthetic
Trait psionic species.png Transcendent Awakening Ap transcendence.png Transcendence Add Trait psionic species.png Psionic
Remove Hive-minded.png Hive-Minded

If primitives were invaded, Assimilation will remove Culture Shock.

Ascension paths

Genetic modification can be used in conjunction with some of the ascension perks.

  • The biological ascension path focuses entirely on genetic modification. Each of the two ascension perks grants 3 additional trait points and reduces the genetic modification projects by 25% as well as unlocking early the Tech gene seed purification.png Gene Seed Purification and Tech genetic resequencing.png Genetic Resequencing technologies respectively.
  • The psionic ascension path adds the Trait psionic species.png Psionic trait that cannot be acquired or removed through genetic modification. At first, only the founding species will get it, but other species living in the empire can get it through the aforementioned assimilation.
  • Choosing the synthetic ascension path will first enhance the empire's every species with the Trait cybernetic.png Cybernetic trait. Cybernetic species are still organic enough to be genetically modified. Finishing the synthetic ascension path will upload all Trait cybernetic.png Cybernetic pops into Robotic bodies, replacing genetic modification with robomodding. Trait cybernetic.png Cybernetic pops are prohibited to be assimilated, as Synthetic empires are always also a Cybernetic empire.

Hybrid species

Xenophile.png Xenophile and Fanatic Xenophile.png Fanatic Xenophile empires that research the Tech gene tailoring.png Gene Tailoring technology can pick the Ap xeno compatibility.png Xeno-Compatibility Ascension Perk and allows the reproduction of two species into hybrid species. Hybrid species take a portrait from one of the parent species and a mix of traits from both parent species, with at least one trait being inherited from each. They also get 1 additional trait point and trait pick.

Genetic modification events

Aside from scheduled genetic modification species can also be spontaneously modified as a result of some events.

  • If a colony in the empire has less than 40% Mod habitability.png Habitability and the Tech gene tailoring.png Gene Tailoring technology is researched will lead 200 months later to part of the population modifying itself to better suit the environment. As a result of the event chain half of the population will gain the Rapid Breeders.png Rapid Breeders,Strong.png Strong and Trait cybernetic.png Self-Modified traits.
  • One of the Horizon Signal events will issue a special project to investigate an escape pod. Not ending the event with any of the next two choices will result in the scientist unleashing a retroviral agent on the empire's planets. The option is given to either limit it to the homeworld or allow it to change the entire main species. The appearance of the modified pops will change, Militarist.png Militarist and Fanatic Militarist.png Fanatic Militarist empires pops will gain the Intelligent.png Intelligent trait and become pacifist, and non-militarist empire pops will gain the Resilient.png Resilient trait and become militarist. Only Authoritarian.png Authoritarian and Fanatic Authoritarian.png Fanatic Authoritarian empires can prevent the change by purging all but one pop from the homeworld.
  • Finishing the Horizon Signal and accepting the Worm's offer will give all Pops in the home system the Natural Physicists.png Natural Physicists and Repugnant.png Repugnant traits and the Trait pc nuked preference.png Tomb World Climate Preference.
  • Forming a Covenant with the Composer of Strands in the Shroud will mutate every Trait psionic species.png Psionic species in the empire roughly every 25 years, changing traits completely at random.
  • One of the anomaly events will give the option to start a Neural Symbiont Special Project if not Auth machine intelligence.png Machine Intelligence. Finishing it will give the option to allow a scientist leader to become a host for a neural slug. If allowed a month later the option to bond the population of the capital with the slugs become available. Agreeing will give 3 Pops on the capital the Trait brainslugged.png Brain Slug Host trait.
  • One of the anomaly events will find a high-speed box orbiting the planet. Any choice except ignoring or selling it will end with opening the box and using one of the substances to instantly enhance the main species with the following trait:
    • Red solution grants Social Pheromones.png Social Pheromones
    • Green solution grants Bioadaptability.png Bioadaptability
    • Blue solution grants Limited Regeneration.png Limited Regeneration


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