Personally I believe there are aliens too. There are simply too many other possibly-inhabitable worlds not to be.
But I doubt they're all humanoid. That's almost to imply there's no possibility a dog could have ever gained higher-order-consciousness. And I think they could have if evolution had taken a different turn. A turn that could have been completely taken (with some other creature of origins we know nothing about) on a different world.
In short, having two arms and legs and a head on top, and walking upright doesn't seem to me to be some sort of requirement for our level of consciousness. It's all about developing mental capacity beyond pure instinct and short term non-complicated reasoning. And whatever body that occurs in will be adapted to the higher consciousness. Even if the head is underneath, it walk on tripods and breathes lava.
