How can someone say, "At the beginning of time, this or that happened..."? and even be relatively certain it's accurate?

They can't.

When did time "begin"?

Unless you were there - at the beginning of time - you don't know, you can't know and, the possibility, the probability, is, that you never will know.

So we make up theories, reasons, possibilities or probabilities of the theory - at times contriving data - so our "proof" holds water.

You can do the same thing with Depends.

All too often theories are offal, no logic involved, just visceral strain.

And what difference does it make today?

Are we living happily ever after?