The Elgin Marbles and mokomokai are examples of what is a very thorny problem, with international and cross-cultural implications. A few years ago, an Australian Aboriginal elder successfully petitioned the British government to return the remains of one of his forebears, although I can't recall the circumstances of the original removal in that case. Whilst most people would regard it as improper to remove, or retain, human remains from just a few generations ago, not all cases are so black and white (scuse the pun). For instance is it improper to remove artefacts of ancient civilizations - you might say yes to those buried in a tomb, say, but what about an axe-head or knife-blade (apparently discarded) in an open area? What is the difference between "stolen" and "found", especially given that some cultures have quite different concepts of "ownership" anyway. And should different rules apply to things "belonging" to Nature, e.g. Should fossils be treated differently to rock paintings? Is it improper to chisel them out of rocks and take them away? But then where would science be if we didn't? Then there's shipwrecks.... And then there's....
I don't pretend to have the answers, just an appreciation of the complexity of the issues.
