Oooh, sorry about that. I remember reading something like that once. But I just found out that it was not 1000 years, but 400 years. Still, compared to Jesus, who was first written about when plently of people who knew him were still alive, that says something.
Of course, there could have been manuscripts about Alexander from eariler that were destroyed, but who knows.
Plutarch et al. were basing all the stuff they wrote on previously existing books about Alexander. Is Plutarch 100% trustworthy? No, nor is any classical historian, but he's a lot better than most.
Plus, quite a bit of stuff about Alexander (more so than just about anyone else from that period) can be verified by archaeology. Notably, the fact that Tyre is now a peninsula and used to be an island. (The most impressive of Alexander's accomplishments, IMO) Not to mention the nearly dozen cities popping up with the name Alexandria. Or the new Greek dynasties in Egypt and the Near East (the Ptolemies and the Seleucids). Or the bizarre fact of the
existence of the kingdom of Greco-Bactria. Alexander left a lot of evidence of his actions.
