A/N: I apologize for this and the previous chapter. I have no idea what happened to the text to make it crush like that and drop some words.
Pokémon Evolution, distinct from natural selection-driven adaptation, is the process by which a Pokémon experiences spontaneous, non-reversible changes in biology, type, and combat potential.
Forcing a Pokémon to Evolve is usually frowned upon. Let the Pokémon have some agency and voice in when it Evolves.
Do keep in mind that severe changes in personality do occur in many Evolutions.
Many different triggers have been found for Evolution.
Accumulation
As mentioned previously, level does not exist. The majority of Evolving Pokémon do so by accumulating energy. Aging and training both provide ways to gather the needed energy.
Mood
Some Pokémon require a state of supreme contentment or happiness in their lives before they Evolve. In the wild, this usually involves having a mate to help them guard the nest. With trainers, keeping the team fit, healthy, happy, and occupied is the way to go.
Moves
Knowing a move triggers Evolution in some Pokémon. In all cases aside from Sylveon, these Evolution-inducing moves are powerful attacks that can protect a nest full of eggs, though some researchers suggest that the moves actually affect the environment in such a way as to mimic the otherwise nonexistent conditions that induce evolution.
Stone
Evolution-inducing stones are a moderately rare commodity. The cost a few thousand credits each. Simply coming in contact with such a stone is not enough to trigger evolution. The Pokémon needs to channel some of their Energy into the stone to cause the resonance feedback that then triggers evolution.
Do note that once Evolved, most Pokémon that use this method cannot learn any damage dealing Moves naturally.
Item
Some Pokémon evolve in the wild using methods that can take centuries or requires environments that humans cannot survive in. Items and systems that provide a controllable means of simulating some of those conditions can induce evolution.
Interaction (replaces trade)
Sometimes social interaction can be a catalyst. Some Pokémon will evolve when given a chance to interact with multiple trainers and learn more about the world.
Pokémon
Sometimes the presence of another Pokémon is necessary to induce evolution. In some cases, simply having the two Pokémon train together would be enough.
Both of Slowpoke's evolutions require a Cloyster. Slowbro needs to have a Cloyster biting its tail, while Slowking needs a Cloyster biting its head.
In the cases of Magnimite and the Beldum Evolutionary line, having multiple of the same Pokémon in the area is required. Three Magnimite become bonded by magnetic force into a single creature. Beldum fuses with another Beldum to become Metang, which then fuses with another Metang to become Metagros.
Environment
Some Pokémon Evolve when exposed to environmental factors that humans cannot replicate, such as strong electromagnetic fields, the energy of ancient glaciers, and the energy of the heart of a forest. Even a natural rainy day can be a trigger.
Time
Some Pokémon require moonlight or sunlight to evolve. This is always a secondary condition to one of the other conditions listed on this page.
Other/Unique
Sometimes a Pokémon needs strange conditions to evolve. These will be covered in the chapter for that Pokémon.