No, people did not know natural selection before Darwin. He spent decades collecting and then analyzing data collected in Galapagos Islands before he made his breakthrough.
It's pure hindsight bias to think that you can go from "I bred the fattest chickens together, who made a fatter chicken" to "Humans evolved from apes who evolved from single-cellular organisms". For millennia, people from all cultures believed that God created humans from the void. In the absence of data, that's as good a guess as you can have. If Darwin concocted his theory of natural selection before he had his data, no one would have believed him. By dismissing the theory of natural selection as something that was "obvious" pre-Darwin you are dismissing his life's work.