On the subject of ancient art: Our discussion was about the archeologic sites in Pompeii and Herculaneum (which were destroyed by an outbreak of the nearby Vesuvius and thus basically preserving a moment in time two millenia ago). Now, archeology back then wasn't what it is now. Back then it was "look what old stuff I found" on a good day and "See? Our people were so advanced back then and they have cultivated this land so long ago, so you don't belong here" or "Wow, you people were primitive back then!" on a bad day.
In this specific example they dug througj the ash and basalt and found basically a gigantic brothel. The whole town was covered in sculptures, mosaics, paintings, and carvings of people during sexual acts - even d**dos. Being the "good Christians" they were they massively covered it up with plaster, completely destroyed it, or - like in the case our discussion was based upon - mislabelled them (a person saving another from falling into a river instead of the actual doggy style sex it was) and filed them away never to be seen again.
Our discussion back then didn't even revolve around whether those statues, paintings, etc. were art or not. Back then they were pretty obviously porn - whether you call that art or not. The important part is that we all believed the ancient Romans were "so civilized" that we labelled their naked statues as art. The findings in Herculaneum and Pompeii however show us the Roman world before the widespread Christianization.
Only in the last twenty years or so have historians gone back through all the stuff found there and re-evaluated most of it. We are now pretty certain that those two cities were no outliers and all of the Roman world at the time looked pretty much exactly like that. There have been other findings throughout Italy, North Africa, even as far north as Germany that go along the same lines but had been covered up in the latter period of the Roman Empire. Maybe even the statues we now associate with the Roman period were originally porn and maybe later someone put clothes on them (which is one possible explanation for the missing arms btw.) or the more explicit ones were destroyed.
This is another reason I think a differentiation between art and porn is rather difficult. Technically, the word "art" only means "artificial", which comes very close to Kamikaze's definition of just "something made on purpose". Of course, there is more and less accepted art in different social contexts and communities...
