No, "God" didn't "put" people on the planet to fuck each other. Fucking existed for billions of years before humans did, and those original fuckers evolved into billions of different species of fuckers, including humans. We're here because we fuck, and if we didn't we'd die out. If you have any evidence whatsoever that some factor besides evolution was involved in making us creatures who like to fuck, I and the entire scientific community would be fascinated to see it.