What do you consider to be "authentic"?

So many aspects of todays cultures have resulted of evolution and influences of other cultures over years and years. Today people toss around the word “authentic” as if it means something.

Is there any such thing as “authentic” any more?
Tomatoes were brought from the New World to Europe and Italians only started using them relatively recently… so is Italian Food made with tomatoes considered “authentic” Italian Food, or is it Italian food with New World influence?

Hypothetical: Authentic Roman jewelry found in ruins, could have been made by a slave from North Africa, using materials from India… is it Roman? North African? Indian?

By today’s standards, what is “authentic”