Private Prehistory

In my WSJ piece, I mentioned in that some 80 percent of the prehistoric caves that have been discovered in France are thought to be privately owned. There’s a bit more to this story:
My discussions with experts in the Dordogne region indicated that many of those who discover such sites on their property don’t report them to the government, as legally required. So there could, theoretically, be another Lascaux or Chauvet enjoyed only by a French landowner and a close circle of friends. Indeed, Rouffignac Cave, regularly open to the public (who travel into its depths on a small electric train), was purchased by someone who wanted the land and, at first, had no idea of the riches lying beneath. (It is owned by the Plassard family, whose son, Frédéric, was later inspired to become a prehistorian.)
There are several possible reasons for keeping caves hidden: Owners don’t want to involve the public sector in their private hectare; they don’t want cave-crazed tourists knocking on their doors; they don’t want to trigger the law that requires them to report to the government any finds of historical, art historical or archeological interest. After making such discoveries, private property owners not supposed to disturb or degrade the site.
There’s another possibility, not mentioned, but easy to imagine, in light of all the disclosures about illicit antiquities activities in other countries: Is there an underground market for France’s version of underground art?