Who was the first shinobi?

Could you please elaborate on the enigmatic question of who the very first shinobi, or ninja, was? It's a fascinating topic steeped in history and folklore. Was it a solitary figure who emerged from obscurity to redefine the art of stealth and combat? Or did the concept of shinobi evolve gradually over time, with various practitioners contributing to its development? I'm particularly intrigued by the potential historical roots of this mysterious profession, and how its early practitioners may have differed from the well-known ninja of later eras.