A set of seven footprints made at a lake about 120,000 years ago have been hailed as the earliest evidence of modern humans on the Arabian Peninsula – a discovery experts say could shed light on the spread of our species out of Africa.
The path by which Homo sapiens spread around the world was full of twists and turns. Genetic studies suggested it was not until 60,000 years ago that a migration of modern humans out of Africa led to a successful spread across Europe.
However, it has been suggested that an incomplete skull found in Greece and dating to more than 200,000 years ago is from our species, while an 180,000 year old Homo sapiens jawbone has previously been discovered in Israel.
A previous discovery in Arabia of an 88,000 year old fingerbone has also pointed to multiple early waves out of Africa – with experts saying the fossil, and nearby stone tools, revealed that Homo sapiens set out east, beyond Israel, far earlier than previously thought.
Now the discovery of the seven footprints in the northern part of the Arabian Peninsula in modern Saudi Arabia pushes this exploration to the east even further back in time.
“This is a story about the expansion of Homo sapiens into the heart of Arabia at an early date,” said Prof Michael Petraglia of the Max Planck Institute for the Science of Human History, a co-author of the research. “It is not a story of coastal migrations, which has been the hypothesised route [modern humans took].”
Writing in the journal Science Advances, an international team of researchers report how they found the footprints in an ancient lake deposit in the Nefund Desert, with dating of sediment above and below the prints revealing them to be between 112,000 and 121,000 years old. The sizes and spacing of four of the prints, they add, suggest they were made by at least two individuals.
The team argue that the size of the prints, the absence of evidence for Neanderthals in the area at the time and the evidence that Homo sapiens were in Arabia almost 90,000 years ago, suggest the impressions were most likely made by modern humans.
The team also found a plethora of animal prints at the site, including those from ancient elephants and camels – but the animal bones showed no signs of butchery, and no stone tools were found. Taken together, the researchers say the findings suggest that the party made only a brief pit-stop at the lake.
“At the time that humans were moving through this landscape, the area wouldn’t have been hyper-arid,” said Richard Clark-Wilson, a co-author of the research from Royal Holloway, University of London. Instead, he said, at that time – and various other periods in the past – it would have been a grassy savannah with bodies of water, offering opportunities for human migration. “Human movements, and animal movements, tend to be linked to fresh water availability,” he said.
While people who walked by the lake have left their mark on history, their fate remains unknown.
“It appears that people repeatedly dispersed into Arabia during more humid periods, when the region was characterised by expansive grasslands and lakes and rivers,” said Mathew Stewart of the Max Planck Institute for Chemical Ecology, another author. “In the intervening periods, when the deserts returned, we suspect that people either died out or retreated to more favourable places.”
Dr Matthew Pope, an expert on ancient humans from University College London, who was not involved in the work, welcomed the findings. “Footprints are so incredibly evocative – they are brilliant for dissolving time barriers,” he said.
While Pope said it was not possible to infer many details about the party from the prints, he said the work added to a shifting view of Arabia in relation to the movement of Homo sapiens out of Africa.“This is a landscape that is productive, this is a landscape that can sustain human populations, so can provide a landscape for dispersal to happen,” he said.