I love Pokémon. I still remember playing Pokémon Red on my berry Game Boy Color, spending hours collecting, training, trading, and evolving as many creatures as I could. (Heck, I still play Pokémon- I’m currently working through Pokémon White right now, and of course I’m working on my Pokémon Go Pokédex.)
There’s just one problem… Pokémon don’t evolve. They undergo metamorphosis.
Evolution is the change in heritable characteristics over succeeding generations. The general idea is that those who are best adapted to their environment will have a better chance of surviving and reproducing. Their offspring, in turn, are better able to survive and reproduce. Those who are not well adapted are unable to survive and reproduce.
Charles Darwin, a naturalist known for his studies in evolution, documented the diversity of life he saw during his travels among the Galapagos Islands. He also collected specimens for study, including a series of birds. These birds had a common ancestor. Certain members were slightly better at getting food than others due to slight differences in beak size and shape. Over time, only offspring who were successful at getting food survived and reproduced. Eventually beaks differentiated, and several species evolved. For example, ground finches developed larger beaks for cracking seeds; warbler finches developed thin and sharp beaks for spearing insects.
Metamorphosis, on the other hand, is transformation. This transformation is not gradual, but involves a sudden physical change where the animal goes through two or more distinct stages. Metamorphosis does not include growth spurts.
One oft-cited example of metamorphosis on Earth involves caterpillars morphing into a butterfly. The caterpillar starts off by building a cocoon. It then digests itself, becoming caterpillar soup. The only thing left are “imaginary discs”- groups of cells that divide and form parts of the butterfly. Once complete, the butterfly emerges.
Basically, if the physical change happens to an individual within their lifetime, it’s metamorphosis. If the change happens within a population over generations, it’s evolution.
Most Pokémon follow a simple chain of change- A becomes B which becomes C. But in some cases, Pokémon follow a branched chain of change, with one Pokémon having the ability to turn into one of two or more options. Eevee, for example, can turn into one of eight different Pokémon (as of Pokémon Moon and Sun): Vaporeon, Jolteon, Flareon, Espeon, Umbreon, Leafeon, Glaceon, or Sylveon. What Eevee turns into is based on exposure to certain objects, places, or traits. (For example, and Eevee exposed to a Thunder Stone turns into Jolteon; an Eevee with high friendship that levels up during the day turns into Espeon.)
This happens in real-life as well. Take honeybees, for example. Within a hive are several castes, or types, of bees. Fertilized eggs develop into female bees. Most of these female bees are fed “royal jelly,” a honey bee secretion, and then a mixture of honey and pollen. This turns the female bees into workers, which are responsible for a variety of tasks including cleaning the hive, building combs, feeding larvae, guarding the hive, and foraging for resources. Once in a while, a female larva is chosen to become the queen bee, the member who is responsible for reproduction in the colony. This chosen larva is fed exclusively royal jelly and develops into the new queen bee. The queen bee mates with drones, male bees that develop from unfertilized eggs.
In summary, your Squirtle didn’t evolve into Wartortle- it metamorphosed.
I just checked- it’s metamorphosed. Maybe that’s why they chose to use “evolving” instead.
Keep calm and science on.