We are biological machines. Sure, we have an awareness of ourselves, but so do computers in some contexts; for example you could argue a certain types of self-modifying or monitoring code has an awareness of itself. It's already been proven that animals have an awareness of themselves when looking in a mirror, such as Dolphins, Chimpanzees, etc. Humans may be a bit further along in our cognitive development but there is no obvious point where you can say "Humans are conscious" because we're all somewhere on a sliding scale of intelligence and self-awareness.