I had as it happens prepared an earlier attempt to address that criticism, Naomi. In the end I can't see the point, really, beyond noting that I'd argue you seem to be starting to ask questions at least two steps ahead of where I think the starting point is, ie that firstly it's important to rule out bias at our end (based on, say, pattern recognition), and ruling out the possibility of symbolism entirely at the ancient peoples' end, before the discussion of alien astronauts can even get off the ground.