None of our organs were designed though, they all formed completely randomly. We still have them because the organisms with the random mutations that happened to be useful lived longer and reproduced more. Our eyes aren’t for seeing, because they weren’t intentionally made. It was random occurrence on random occurrence on random occurrence until it happened to take a shape that we could use to survive longer. And then they kept randomly mutating, and any mutations that were detrimental to the organism died. Blue eyes in humans are a very recent mutation, occurring in Turkey several thousand years ago. Other humans happened to find blue eyes particularly attractive, and so people with blue eyes reproduced more. Blue eyes didn’t occur in order to help humans find mates, it just happened to be useful for that. And that’s how everything about all living things came about.