The Universe is so vast that there has to be another place out there that has the conditions to support life. But the only understanding of how life is created is on Earth, it could be that in other places life is supported a different way. How do we really know that life cannot live off of something other than water and oxygen. We will never know until we actually see life on other planets. The dinosaurs might have been domesticated had humans actually lived then.
Dumb animals are the hardest ones to be domesticated.
Also, the only ones we could domesticate would be herbovaures, carnivores would just eat us. If humans were smart enough dinosaurs could have been domesticated.