Mars and Earth pass closer to each other on Wednesday than at any time during the last 60,000 years. Helen Briggs looks at what life might have been like the last time it happened in 57,617 BC.
Smoke drifts from a fire at the foot of a cave on the shores of what is now southern Africa.
Darkness is falling and the first stars glitter in the night sky.
To the south east, a blood red planet looms ever larger, outshining almost everything around it.
A group of Homo sapiens hunched over the flames nudge each other and point to the sky. Their primitive faces, rapt with attention, are lit by sparks flying from the fire.
One individual picks up an animal bone and starts scratching away at a chunk of powdery rust-red haematite, an ore ground down for cave paintings.
Thousands of years later, the descendants of early modern humans will find the object, call it art, and wonder what it might have meant.
Out of Africa
This is a flight of fancy, of course, because we will never know what went through the minds of our ancient ancestors when Mars and Earth last passed within 55.6 million kilometres or so of each other.
At the time, early modern Homo sapiens were beginning their great journeys out of Africa by boat or raft to south east Asia.
They shared the planet with the Neanderthals, who hunted the plains, forests and mountains of Europe, the Near East, and Central Asia.
Neanderthals made tools and could probably speak
Clive Gamble, professor of archaeology at Southampton University, southern England, says it was a very different world "poised on one of the great changes of the planet - we were about to become the only species on Earth".
Probably even the less advanced Neanderthals would have been aware of the wandering of the planets, he believes.
"Neanderthals certainly weren't stupid," he says, "and although I can't prove they had a knowledge of cosmology, they were certainly aware of their environment and would have noticed changes like that."
Early humans would have been familiar with the cycles of the seasons, which brought them food from migrating herds and fruits and berries.
It would be thousands of years, however, before sketches of the heavens were laid down on rock or bone.
Some believe that notches carved on antler bone by the Cro-Magnon people of Europe some 25,000 years ago depict the changes in the phases of the Moon - a rudimentary lunar calendar.
A 77,000 year old piece of haematite from South Africa inscribed with geometrical designs - the earliest known art object - precedes that.
It could have been some form of early notational system - as to what, we can only speculate.