However, given the extreme antiquity of the genre, taphonomic logic dictates that this is only to be expected.
It is noteworthy that some cupule-sites have been re-worked by later artists, sometimes several thousands of years later.
They can occur on horizontal, sloping or vertical rock-surfaces, but very rarely on overhead rock ceilings: a notable exception being at Grotte Boussaingault in France.
As a rough guide, cupules found on surfaces with an incline less than 45 degrees comprise over 50 percent of all known examples.
Are Cupules a Genuine Type of Prehistoric Art?
The actual term "cupule" was invented recently by the world-famous archeologist Robert G.
This category also includes gnammas (rock-holes enlarged by chemical weathering) and tafones (hemispherical hollows typically evident in sandstone, dolerite, limestone, rhyolite tuff, and granitic rocks).
When identifying man-made cupules, such identification is usually assured when there are traces of the tools employed in making them, or where the hollows are arranged in such patterns that intentionality is clearly evident.
Many cupules, including the oldest specimens at Bhimbetka and Daraki-Chattan, occur on very hard, erosion-resistant rock types,such as quartzite, gneissic granite and even crystalline quartz.
However, cupule-making is not just a type of Paleolithic art.
In India, for example, home of the Bhimbetka Petroglyphs - the world's earliest art - cupules were also made during the era of Mesolithic (10,000-6,000 BCE) and Neolithic art (6,000-2,000 BCE onwards) as well as the preceding Upper Paleolithic.
Be this as it may, true cupules have occurred from the earliest tool-making cultures.
Indeed, the oldest art on every populated continent consists of linear grooves and cupules.