That's how we know this. And one of the first pieces of literature in human history was the Epic of Gilgamesh, who was one of the early kings of a city-state in Sumer where the Sumerians lived. And you can hear from this passage how they viewed life itself. Gilgamesh, whither are you wandering? Life which you look for you will never find. For when the gods created man, they let death be his share and withheld life in their own hands. Immortality, you're not going to find it, Gilgamesh.