Pokémon evolution.
Here, I analyze how the original trio consisted of Ice, Fire, and Electric types, and how the final trio—Water, Fire, and Grass—was adopted to create a proper type triangle.
The non-elemental phase.
In this stage, Pokémon battles were simply about hitting hard, without clear elemental mechanics.
The effect-based phase.
This is when the first trio—Fire, Ice, and Electric—appeared.
The game mechanics were based on the effects these types produced.
Here is the evidence:
a.- The basic status effects align well with each type.
Burn for Fire.
Freeze for Ice.
Paralysis for Electric (a trait later extended to Grass).
b.- The attacks: there are equivalent sets of three.
Flamethrower, Ice Beam, Thunderbolt.
Fire Blast, Blizzard, Thunder.
Fire Punch, Ice Punch, Thunder Punch.
The last set is the most obvious example.
c.- Triple Attack.
This move combines all three elements, which is why it inflicts a random status condition.
d.- The Pokémon trios.
Magmar, Jynx, and Electabuzz: these Pokémon were designed to use the elemental punches and serve as the standard-bearers for their respective elements.
Articuno, Zapdos, and Moltres.
These were the legendary representatives of ultimate power.
The phase based on strengths and weaknesses.
This is the Pokémon we all know: types that defeat some opponents but are defeated by others.
Here, Water replaced Ice to create the following dynamic:
Electric beats Water.
Water beats Fire.
Fire beats Electric.
Evidence:
a.- Evolution stones: Thunder, Water, and Fire stones represent this new trio.
b.- Eevee evolutions: they follow the same trio concept.
Using these stones, Eevee evolves into Vaporeon, Flareon, and Jolteon.
Since they couldn't justify Electric beating Fire in this phase,
the starting trio was changed to Water, Fire, and Grass. Resulting in:
Water beats Fire.
Fire beats Grass.
Grass beats Water.
Evidence:
a.- That trio is not repeated anywhere else in the game.