This was an oral tradition, so do not confuse the language called "sanskrit" with the writing system.
Then, too, Indo-European writing systems are all relatively recent arrivals. The oldest stuff is in Mesopotamia. It was developed by the Sumerians, a nomadic people who ALSO built cities, wrote laws, developed weights and measures, and INVENTED writing.
They were non-Indo-European.
Rune alphabets used for Indo-European languages were actually developed AFTER the Roman alphabet. The ancients knew that to be effective an alphabet must work well with the language which is going to use it for writing. The Greek alphabets drew upon earlier Semitic alphabets, and they, in turn, drew upon Egyptian hieroglypic systems (combination of ideographs and syllabries), and those systems, in turn drew upon the earlier Sumerian system.
The Chinese ideographic writing systems begin with characters not all that different than those used initially by the Sumerians and are believed to have been devised by Sumerians. The earliest written Chinese is in such characters.
Going back a few thousand years, the oldest ideogram systems we can hope to understand are located in the Kola peninsula in Finland and Russia.
These systems are so ancient few of the stories have been derived. A number of them have to do with the day to day life of Sa'ami-like cultures, and tell stories about a fellow probably named Lot who wanders around following reindeer and getting in trouble with people who live in settlements.
Pretty exciting stuff eh!
It all depends on who your authorities are.
I accept the statements in the Puranas themselves, and there is much authenticating evidence, with more being discovered or admitted every year.
According to the Puranas, Vedavyas wrote down on leaves (which were used as writing surface up until a few hundreds years ago) 5000 years ago at the advent of the Kali Age. So the Sanskrit written characters are 5000 years old. Much of what has been accepted as standard Indology was knowlingly fabricated by British historians and linguists in order to denigrate the country they invaded and plundered.
Statements from some of these early Indologists have been found wherein they admitted their purposeful lies about the great antiquity of the Vedas and archeological evidence.