3000 years ago is about when the first recognizable letter A was drawn.
https://en.wikipedia.org/wiki/Proto-Canaanite_alphabet
The amphora vessel design is neolithic, so you could add on another 10,000 years if you want to trace the roots of the @ symbol tenuously into pottery. There's such a thing as too much context.
But what if we add the role that harnessing fire had on the development of pottery and the amphora? That easily adds another 770000 years