Frank-you are asking the right questions but the answers are allot harder to answer. When I was in my first actual archaeology field class, the first thing they told us is to look at the site area and "picture it" in your mind as to how it looked in the past-not today-what the environment looked like at various times and what (if anything) would be left today to pick up and look at and what things were actually there to look at today! To illustrate this, they created a site by throwing a bunch of artifacts,rocks, bones and things (some in circles,some buried, some random ) around a juniper tree and telling us Okay, what happened here and letting us come up with what happened and when it happened, was it a one time event or was it several events-or maybe even none at all because it all took place naturally! Lots of possible answers and there in is the fun of tiring to figure out the "Who's, What's, Where,Whens and Hows" based on what you see, know and can surmise or guess.
Skis' rock art is probably in the .Great Basin or high desert some where, so that's a start and ,generally speaking, except around major food sources, population density was low when compared to say the California Central Valley or parts of the southwest. and was based on the small family unit because there was not enough "food" around to support large groups. What does the rock art look like-the same or different styles, were there breaks between styles or types thru time. There were very dramatic climate changes over time in the Basin-with long periods with no one there or at certain times there were major increases in populations as climate change or other things drove different groups thru the area. When you think that this type of process was going on for maybe 15-20,000 years or so ago, the numbers of people thru that area and who used those rock art sites, are pretty hard to estimate.
And we have not even started of thinking how, why and how often they were used and for how long! Sorry, guys Ski's TR seems to turned on my old archaeological thinking self, and I don't what to seem that I'm and old know-it-all and I am not trying to hi-jack Ski's great TR-so that said, best guess and based on what we know about the 4"W's" and 1" H", not that many people probably knew about or used that "exact " rock art over maybe the last couple of 1000 years or so! Best I can do for now, get me out in the desert sometime. Remember that "created ark site" story next time you find something interesting while out WTWing! Sorry again!
Smoke