I will be upfront about it - I am skeptical of our tradition about the Torah being given on Mount Sinai, and suspect that Judaism is a man-made religion. It's not that I don't want Judaism to be true, I do. It's just that it seems to make claims about this world that are falsifiable, and that I consider to be falsified. So I am asking about one of those claims here, hoping that I will get some good answers.

The four rivers. In Genesis 2:10-14 we are told that a river emerged from the garden of Eden and then parted into four heads:

The name of the first is Pishon; it is that which compasses the whole land of Havilah, where there is gold... And the name of the second river is Gihon; it is that which compasses the whole land of Cush. And the name of the third river is Hiddekel; it is that which goes towards the east of Assyria. And the fourth river is Euphrates.

There is no river in the world that parts into the four rivers mentioned. Although we are not acquainted with any river called Pishon, we know that Gihon is only a small spring in Jerusalem. The Hiddekel (which is the Hebrew name of the Tigris river) and the Euphrates are not two "heads" splitting off of one major river; the opposite is true: at Al-Qurnah (Iraq) these two rivers join to form the Shatt al-Arab. Some Rabbinic commentators on the Scripture (Rashi and R' Saadiah Gaon, for example) interpreted the name Pishon as referring to the Nile, but then we have a serious problem: there is not, and never has been, any connection between the Nile and the Tigris or the Euphrates.

Does anyone have any idea how a river could have split into these rivers and there be no evidence of it today?