Mark making

'Traces left by our ancestors from 25,000 years ago' the softly spoken guide explains. 'Wow' whispers the American woman in breathy response. But what exactly are we to make of this statement, this 25,000 years ago? It's calculable but still somehow incomprehensible, out of reach - so many generations ago. Let's face it, it's hard enough to imagine the recently deceased let alone those we have never met. And yet here is the gracefully drawn outline of a horse. A carefully executed red ochre line on the wall of the cave. 'We know how but we don't know why' the guide says emphatically. Science can tell us the exact composition of the materials - charcoal, brushes, sticks, hands and pigments. And it can also give us a pretty accurate idea of when this particular horse was drawn, but the purpose, the motivation for making this image escapes us. Yet it is obviously, yes undisputedly the form of a horse. That much speaks clearly and unambiguously across unknowing time. And since we are all convinced that the ability to draw like this is peculiar to the human species, which ever you look at it, this is an act of human communication. Whether its survival in this labyrinth of limestone caves is accidental or not makes little difference. Perched on our millennial ridge we gaze into the mists of human time, knowingly squinting at a hazy horizon. We were here before, leaving our mark.