It's a very valid point of view Mr H.

There's been a nice constructive chat about it here:
http://www.heritageaction.org/forum/viewtopic.php?t=333

Mind, from what I've seen, the Galician stuff is beyond doubt, both in terms of artificiality and antiquity. (It makes me droool just to think about it). Though they do have a rep for being in especially awkward to find places, so mebbe not so a good way to 'get into' rock art.