system
Given the following post, respond as if you're commenting on Reddit:
human
[pokemon] how exactly does trade evolutions work

So you know how some pokemon can only evolve after being traded? 

I've been wondering how that is the case. 

The trade mechanism is man-made, which would suggest the evolutions being artificial somehow. Yet most of them also exist in the wild, away from trainers. 

But if that's the case, why can't they evolve otherwise?
gpt
I read somewhere that Graveler and Machoke were only supposed to evolve when those two specific Pokémon were traded because their DNA gets mixed up or something. It makes sense, Graveler has four arms, Machamp has four arms. Machoke has pointy teeth, and Golem has pointy teeth.