Sooty fingerprints of sister species

In 1957, my brother Richard and I travelled on our 59cc NSU mopeds from our home in Wimbledon to central France to spend our summer digging in the cave of Arcy-sur-Cure. We delved deep into the prehistoric layers in a sequence that saw the transition from occupation by the Neanderthals into the arrival of modern humans.

So, I have naturally been fascinated by the recent discoveries in the Grotte de Mandrin, located a bit further south in the Rhone Valley, where Ludovic Slimac and his team have been making some really remarkable findings.

Traditionally speaking, modern humans are supposed to have arrived ultimately from Africa and the Levant into Western Europe, precipitating the sudden extinction of the Neanderthals about 40,000 years ago. The Rhone Valley is and was the highway between the Mediterranean and the plains of northern Europe, and Mandrin cave is strategically placed to attract migratory human hunter-gatherers.

The occupation layers accumulated over tens of thousands of years and they contain the stone tools made by those who sheltered there, their bones, hearths, food refuse and a source of information that has literally thrown a bright light on a hitherto untouched topic. And that source is, of all things, soot.

With every campfire lit, a microscopic film of soot rose up and adhered to the cave roof. Annually, that soot was covered by an equally thin growth of stalactite, forming layers just like tree rings that under a microscope reflect the season of the year. Fragments of roof regularly cleaved off, to be incorporated in the cultural layers.

Painstakingly, Ludovic’s team have combined these into a unique record of visitations to the shelter. Over a 10,000 year period, there were nearly 300 separate occasions when humans lit their fires there.

Under the traditional history, the modern humans migrated up the Rhone valley from the Mediterranean shore to precipitate Neanderthal extinction. But the soot tells a very different story. The cave sheltered Neanderthals briefly and on many visits until about 54,000 years ago. Then there was a sea change with the arrival of modern humans, at least 10,000 years earlier than the traditional story.

But it did not lead to any sign of contact between the two human communities, nor the extinction event. Indeed, the Neanderthals returned to their traditional base, before there were yet more visits by modern humans. The soot sequence is so precise that we now know that barely a year separated some of these visits.

One of the vital chapters in the human past has been illuminated by ancient fires and soot. For hundreds of generations those two different humans lived isolated alongside each other.