I've been thinking about this,and if it is real-how may the drawings have been made and in what context?
The drawing are in hard to reach places,and some go up much higher than a persons height.
They depict many different animals,plants,weapons,hunting,and maybe textiles/building items.
With that in mind,my theory is that this is a form of school or university for those coming of age in ancient times.
A kind of initiation into adulthood maybe-
The tricky placement of the images would take a person who knows the lay of the land,and how to climb to reach the drawing areas-Just getting there
proves to the tribe that you are worthy of learning more/showing your knowledge/making images on the wall.
To paint high on the wall,certain climbing and or building skills must be known-use of the correct type of vines for rope,maybe the building of
scaffold like structures.
Then the painting itself-maybe they were asked by the elders to paint a picture of a skill they know,hunters would paint hunting
scenes/animals,weavers would paint textile patterns etc.
Initiation complete-the painter is now a full adult member of the tribe.
Repeat with generations of people from the same tribe,and we are left with this vast set of images from a bygone age.
My other theory is that it is a form of "prayer wall."
The location is good as its high up(closer to the gods).
The prayers are in the form of images-asking gods/spirits to send them this/that animal to hunt,showng the gods textiles they made to honor them
Just some ideas...probably way off-maybe Banksy will tell us he did it