What it means to be human? Well you are human because you can think as the books say. I don't know we are humans because we are humans. We could call ourselves amoba too...
Why are we alive? I'm alive to do hings or make things what only I can do, it doesn't matter how small it is maybe for one person it's the world itself. I believe I have a role what I should do while I'm alive, and maybe in my next lifes too ;)
Well I know I made iron circle from wood ( as we say here :P) but that's what came to my mind.