Joking apart, we don't know whether man has a soul or not. We don't know know what consciousness exactly is. We don't know how to differentiate between dream and reality. Don't be cocksure that there is no spirit inside a man.
Well, your idea of spirit doesn't fit with how other people perceive it. There are many modes of the consciousness. The human race doesn't even know the truth of themselves and their origin, let alone anything else and how the laws of physics originated.
The distinction between dream and reality is a very serious issue. You're quite right. There is no certainty that we are not perpetually dreaming, and that all our sciences and arts are but the illusions of a dreamer.
Brain? Did you talk about brain? ha ha ha! Ok, I have a car and I know (discovered) how it works. That's all very amusing. But that doesn't say anything about me. The car isn't me, though it takes me around the town. The the sense of 'I' or 'ME', are very distinct from the brain. Soul is a real possibility.
Even, that we can study the brain, itself is a strong indication that consciousness is nowhere solely dependent upon the brain.