Just a handful of people are thought to be responsible for incalculable damage to archeological sites along the Cumberland River.

One, believed to claim Native American heritage, leaves tobacco offerings at the graves he robs. (“Such a strange way to placate your karma,” muses Aaron Deter-Wolf.) Some are actually known by name, but there are few resources to prosecute them.

The looters’ methods, though, are similar: They spend their days on the water, they use specialized tools, and they’re savvy. “They’re [selling] mostly through private collections, antique stores, artifact shows—things like that—so it’s really hard to police from a digital perspective,” Deter-Wolf says.

The rise in methamphetamine use, especially in rural areas, has added a new twist to the very old problem of grave robbing, Tanya Peres notes. In the Southwest, looters now trade Native American artifacts for drugs, she says.

While no definitive link between looting and meth has been established in middle Tennessee, “we’ve been told that a number of these guys are tweakers—but that’s anecdotal,” Deter-Wolf says. “From an objective perspective, looting is a black-market economy, and only certain things move in that economy, drugs and weapons being two of them.”

Whatever their motivation, Peres says, looters share culpability with collectors who willfully ignore the source of their coveted artifacts—and make grave robbing big business.