No matter where we came from, how we got here or who we are. The doubt that humans are wonderful creatures of the planet is one of fools.
Those who believe that human life on earth is meaningless, tell me first, what other animal can sing almost like a bird? Swim almost like a fish? Kill more than the lion yet save more lives than it should?
What other animal draws unimaginable things onto paper, builds unfathomable structures on land and fly through the air without wings? And then we doubt our knowledge.
If 'why' is a question only relevant to humans it is only because we were finally able to reach such a meaningful thought, like the birds were finally able to reach the sky.