Self portraiture has been around as long as people figured out a way to see their own reflections, I'm sure.
"Selfies" though, fall into the category of things that are off-topic for APUG. I'd see a "selfie" as strictly a digital photograph, ideally produced with a smartphone, for immediate posting on a social media site on the internet.
I have a cousin who made a thing of holding his 35mm Olympus Stylus Epic at arm's length and taking photos of himself with everyone in the family sometime back in the 1980s I think, and I wouldn't call those "selfies," because we didn't have social media then.
It's more about posting the image on an internet site where your friends can see it, than the act of capturing your own image on some digital medium.