Understanding art my idea of art is that it:
1. is something created by someone out of an urge or desire, and appreciated by people that also have urges or desires. like, it's not meant to ensure your survival or physical well-being, but it can make you less depressed and more fulfilled.
2. directly appeals to the senses. like, inventing a new scientific theory definitely would be fulfilling as well, but it's not exactly fun to look at or listen to, unlike a song or comic.
in contrast, a stone ax is probably not a piece of art because it's solely created to destroy (but also, build) stuff. there's also not much about it that can be appreciated with your senses.
on the other hand, a song can be a piece of art because it's made by and for certain human urges, and can be pleasing to listen to.
also, i don't think how big the audience is determines whether or not it's art, so nothing ''starts'' or ''ceases'' to be art.