And herein lies the nub: are natural animal effluences to be deemed as unfriendly as unnatural pollutants? Is this an indicator of how far lost some of us in our culture have become, or merely an important denominator of where Nature can be 'bad', so we can be aswell?

But on the other hand, relating to what you ask Branwen: don't you think issues such as this one should be studied, in order that we can ascertain the damage Nature can have upon aspects of her own body (in this case, stones, that have been inflicted with human etchings) by raining upon herself, in comparison to some of her animals urinating on those said human etchings? Is animal dung to be banned from the outdoors in case it infects some important archaeological site? Is urine worse than bird-droppings? Wot should we do!!!? ;)