I'm not sure about that 3500BC, but it was certainly widely known and treasured. Here's a fun quote: Pisthetærus Hand me the cheese-grater; bring me the silphium for sauce; pass me the cheese and watch the coals. Heracles Mortal! we who greet you are three gods. Pisthetærus Wait a bit till I have prepared my silphium pickle. From Birds by Aristophanes
Who can be? that said, IF: - Minoan civilization is dated to 3500BC and IF - the Minoans had a glyph for it and IF - Alexander the Great was already looking for a substitute in 350 BC THEN It's safe to assume the cultivation of silphium predates the Mycenians, and also likely to presume that it had attained permanent cultural importance with the Minoans, especially as the Minoans were matriarchal and had a much more driving need for effective birth control.