Ten years ago, an Irish pub owner was clearing land for a driveway when his digging exposed an unusually large flat stone. The stone obscured a dark gap underneath. He grabbed a flashlight to peer in. "I shot the torch in and saw the gentleman, well, his skull and bones," Bertie Currie, the pub owner, said this week. The remains of three humans, in fact, were found behind McCuaig’s Bar in County Antrim, Northern Ireland. And though police were called, it was not, as it turned out, a crime scene. Instead, what Currie had stumbled over was an ancient burial...