If there were any such thing as evolution why wouldn't monkeys have evolved, too. Why would some things remain trees, grass, dogs, cats....
They have.
Monkeys and apes have a common ancestor. Go back further, and you find a common ancestor for all mammals. From that ancestor evolved all the mammals we see today.
This is not a guess or conjecture; the evidence is massive. The only mystery is, why a few folks find it controversial.
"If there were any such thing as evolution why wouldn't monkeys have evolved, too."
They have. That's why there are many species of monkeys. It's also why old world monkeys differ dramatically from new world monkeys.
Check it out on Google.