Evolution
and the Reasons Behind it
Everyone knows that most Pokémon evolve at some point or another, typically getting quite a bit stronger when they do. But why? Why don't they just start in their powered-up forms? Surely that would make life a lot easier for many Pokémon that would otherwise be killed by something stronger than itself.
The simplest way to think about it would be as a form of natural selection. If the Pokémon have to spend time surviving in a weaker form, this ensures that only the truly capable will survive to the higher levels of evolution. At first glance this appears to be the truth for much the same reason as natural selection in our own world. If only the stronger ones survive long enough to mate and pass on their genes, the species as a whole gets progressively stronger. In practice, however, this theory does not hold.
Why? Think about it. Barring the true baby stages, most first stage Pokémon can breed. There's even the strange case of the Nidoran line, in which only the lowest stage of the female can breed. This (however disturbing the thought is) technically means that a Pokémon could be born, mate, and then immediately die, hence completely destroying the reason for natural selection. So what's the true reason?
Perhaps many of the higher evolution stages simply require more energy and strength to sustain the life of the Pokémon. When Pokémon evolve they generally gain new capabilities, sometimes even new types. Their bodies need the resources to support these new abilities, a more extreme case being something along the lines of the sudden ability to fly, as in the case of Vibrava or Salamence. This idea is relatively akin to the caterpillar and butterfly of our own world.
Pokémon couldn't be born with the strength and abilities required for these higher stages of evolution: that would require too much development, such that the Pokémon would be sucking too many resources from the mother and endangering her life. Thus they are required to gain the strength and stamina through battling and training. Once there's a considerable excess of resources available in the Pokémon's cells such that there's enough to sustain their current level of being and still do more, their bodies go about putting it to good use - namely using it to form the cells and such necessary for the new physical structure and abilities of the Pokémon's evolved form.
There. A simple and logical explanation, not even too brain-hurting. This certainly doesn't cover the entirety of Pokémon evolution, but it's about as far as one can go without making it into a full research paper. And surely you wouldn't want to read that ;)
