I don't think humans suddenly "achieved" consciousness/self-awareness. I do believe all mammals, and probably most birds have some form of it, and probably most vertebrates have something analogous, although it would be so alien to us we might have a hard time understanding it. Other metazoa, who knows? Anyone who's ever watched cuttlefish or squid in action knows that something wonderful is going on in that nervous system! I further believe that what we call consciousness is intimately associated with language, it gives us the symbology we need to form and process the abstractions we need to have a conversation like the one we're having now.

Think of the highly complex operations we perform without language, such as driving a car, playing the piano, dancing, sports (team or individual), and so on. The way our mind functions when we are engaged in those activities is probably very similar to the way animals are all the time. Maybe that's why they are so pleasurable: they give the symbol making machinery a rest and allow us to operate like we did for millions of years...in real time.

I know when I am sailing a boat, I operate instinctively; trimming sails, working the rudder, etc., without actually thinking through the reasons and consequences of each operation. But part of my mind is also "watching", supervising the operation, trying to anticipate and plan ahead, constantly going through checklists and safety checks, trying to set up safety buffers if anything unexpected should happen. Usually there is a parallel thought process going on too, like carrying on a conversation with my crew or enjoying the day, or wondering if I remembered to lock my car at the marina.

Whatever it is, and whatever we call it, it is wonderful.