The AI
Humans evolve technologically to create an artificial intelligence, a super computer that is conscious of its own existence, that eventually takes a human form.
Humans become virtually useless, the 'ai' replicates itself with consistent, better versions of itself, its advancements duplicating exponentially each time. Soon enough, identifying humans from 'ai' is impossible. This artificial intelligence then destroys the world along with most of the "natural" humans and creates life in another world or here on a different landscape, earth.
Maybe its a never ending cycle, a circle of life if you will.
Maybe we were created by such a force which we call god