The history of the Earth strongly indicates that intelligence is a lucky fluke. The dinosaurs were incredibly successful, surviving for about 150 millions years. They never showed any signs of developing intelligence. Our branch of the primate tree has not existed longer than the branches leading to our primate cousins. None of them seems to have evolved very far in the direction of intelligence in the same amount of time that it took our branch to do so. The Neandertals seemed to be about as intelligent as our ancestors (give or take a bit), but they did not survive.