We are talking past each other, I would not consider a few religions being able to pass down information about that specific religion to future generations as humanity as a whole being able to pass down information reliably. Especially given that the "Vedas" is wholly useless information while things like the Pythagorean theorem were discovered, lost, then rediscovered. We've only recently rediscovered how Romans created concrete?

Also given humanity has existed for many years longer than 4000 years and 4000 years really only represents 160 generations of humans I don't consider that impressive.