It is hard to know exactly where in the history of the universe we are at. It is very confusing when some of the old native stories suggest we are in the fifth world of people, while others suggest we are only in the fourth, and may yet create a fifth. From the fossil records its suggested that there have been five major extinction events. (Depending on how and where you construct that criteria.)
Looking at the panel in this way, with a single pictograph representing all the peoples of a previous world, suggests the longer span of mythic time. One that is much greater than the rendering of a scientific timescale, limited to the current known world. It is possible that the blank, sanded spot on this wall is an important clue and likely just as important for us as the painted pictographs. The unshaped space suggests unformed, unknown people who will enter the next world. In mythic language, old creation stories recount more than once, ways that some people have disembarked from a corrupted world and moved into the next.
Also, don't miss the dual set of faces seen in the stone to the upper left of the pictographs in this photograph!