In everyday spoken English (USA) we would say something like "The tree is older than I am," or "The tree is older than me." Age would be assumed when you say older. "the age of tree is older than human" isn't clear enough. Are all trees and humans being referred to, or specific ones? Good luck! English is a mix of at least six languages, it can be frustrating at times but keep on ;-)

You can simply say, "The tree is older than me."

Yes, those adjectives would be used to show contrast between two nouns. That phrase is a correct example, but it would best be phrased as "the tree is older than the person".