I’ve noticed that most of the ancient marbles in art museums tend to be labeled “Roman copy of Greek original”. It’s very rare that you ever see an intact Greek statue or bust. Two questions about this:
If the Greek and Roman versions were both existent and in roughly the same condition in Roman times, why did only the Roman versions survive to this day?
And are they actually good copies? The Roman ones are usually considered to be excellent works, but are they just pale imitations? Have they ever found a Roman copy of a Greek statue and the original and compared them?
One of the simplest and most often accurate explanations is that there can be only one original statue but there may be many copies. Popular statues may have been copied dozens of times…or more! So we are more likely to have a surviving copy than a surviving original just because there were more copies out there.
And yes, sometimes it is possible to compare the Roman copies to the Greek originals, although the latter may not be completely intact. The quality of the copy depends on the skill of the artist. Some were quite good, others less so.
Aside from which, the high age of greek civilization waned as the Roman one waxed. I.e, Rome is a lot closer to our time than Greece. Sometimes 500 years makes all the difference. There may also be some differences in how well they were taken care of: ROman cities tended to be inhabited continually into the modern era. Greek sites more often are not, I think.
Actually, most of the Archaic to Classical Greek art we have is from Greece. It was the later Classical and the Hellenistic Period (3rd-1st centuries) which saw the proliferation of Roman copies.
Another contributing factor is material. Many of the Greek originals were bronze, which doesn’t last as long as marble for physical reasons as well as sacking and subsequent resmelting ones. You can tell when the marble is copied from a bronze by the tell tale supports. Artists either left them as posts or placed the statue by a tree.
Another thought, related to Lamia’s point about originals vs. copies: Not only will originals be (obviously) less common than copies, they’ll be far more valuable, over and above what you’d expect based on their relative rarity. This, it seems to me, leads to two predictable results: The rare originals will likely be hoarded away for safekeeping (I bet the Vatican’s got some amazing stuff in their collection), and, on the flip side, a vandal who wants to make a point will be more interested in destroying the original than the copy. Both factors further contribute to the rarity of original objects.
There were also a whole lot of Romans. Tens of millions of people in the Roman empire. The Greeks never approached that number. More people = larger market = greater demand = more product.
You can also see this phenomenon in tile work. A lot of mosaics from Roman times are copies of Greek paintings on wood. Here no examples of Greek painting survive yet we have lots of mosaic. I think the number of full figure bronzes could be counted on one hand.