That might sound of academic importance only, but it could be crucial to our understanding of drawing more generally – starting with its origins. Over the last few years, prominent researchers such as Michael Arbib at the University of Southern California, have begun to consider that gesture and hand signs may have developed before speech – partly because other apes find it much easier to master gestures and sign languages, whereas they can never speak. Given his findings, Cohn suspects that we should add sand drawings to those early proto-languages. He imagines a situation where our ancestors were trying to communicate about a hunt, and so started copying animal tracks in the sand or soil as they discussed the best strategy.

Whether or not this view of the past is true – and Cohn readily points out that it is simply a “pet theory” that would be very difficult to prove – the sand drawings might at least help us reassess cave paintings, which probably came much later in evolutionary history. In the past, some people have tried to read them as masterpieces along the lines of western art – where a painting is produced by an isolated genius and left for posterity. If you look at the fleeting narratives of the Australian desert, however, it is just as possible that the drawings were constructed for active, real-time storytelling. “I scoff at any notion of the lone artist sitting in a cave drawing,” says Cohn. “It seems to me, at least, that these things should be seen as communication from an individual who is speaking and drawing in real time – whether it was a ritual, or just a guy trying to keep the kids entertained by drawing on the wall and telling a story.”

More intriguingly, a linguistic view of drawing might also explain our behaviour today – including our instinct for doodling in the margins. Young children, after all, are well known to go through a “scribbling” period where they will pick up a pen or crayon and make their mark on paper, walls and floors or any other surface they can get their hand on. There are also some signs that these drawings are rudimentary attempts at communication – the size of the random squiggles seems to correspond to the size of nearby objects, for instance. In light of Cohn’s work, this instinct could just be the graphical equivalent of “babbling” – the cooing noises that all babies make as they make the first steps towards speech. Perhaps we are just hard-wired to communicate in as many ways as possible and our environment determines which path becomes more dominant.