Approximately 120,000 years ago in what is now known as northern Saudi Arabia, a small group of Homo sapiens stopped to drink and then forage a superficial lake that was also regularly frequented by camels, buffalos, and elephants much bigger than any species currently known. The group of people may have hunted the big mammals, but they did not linger around for long, using the water body as a waypoint on a longer journey.
This incredibly detailed scenario was reconstructed by scientists in a new study published in the journal Science Advances on Thursday after discovering ancient human and animal footprints in the Nefud Desert, which provided new information on the routes our ancestors took as they left Africa.
A Unique Form of Fossil
Today, the Arabian Peninsula is known to be the massive, arid desert that would have appeared hostile to early people and the animals they hunted down. However, studies over the last decade have shown this wasn’t always the case – because of the natural climate variation, the area was much greener and more humid in the period known as the last interglacial.
“At certain times in the past, the deserts that dominate the interior of the peninsula transformed into expansive grasslands with permanent freshwater lakes and rivers,” explained study co-author Richard Clark-Wilson of Royal Holloway.
The paper’s first author Matthew Stewart, of the Max Plank Institute for Chemical Ecology, Germany, said that the traces were found during his Ph.D. fieldwork in 2017 after the erosion of overlying sediments at a lake called Alathar, which means ‘the trace’ in Arabic.
“Footprints are a unique form of fossil evidence in that they provide snapshots in time, typically representing a few hours or days, a resolution we tend not to get from other records,” he said.
Seven Hominin Footprints
The footprints were dated with the help of a method called ‘optical stimulated luminescence,’ blasting light at quartz gains and measuring the quantity of energy generated.
Overall, seven out of hundreds of prints found were positively identified as hominin, as well as four that, considering their similar orientation, distances from one another, and variations in size, were read as two or three individuals traveling together.
The scientists assert that these belonged to modern humans, as opposed to Neanderthals, on the grounds of the fact that the extinct group isn’t known to have been present in the broader Middle East area back then, and based on stature and mass, could be deduced from the prints.
“We know that humans were visiting this lake at the same time these animals were, and, unusually for the area, there’s no stone tools,” said Stewart, which would have suggested the humans made a longer-term settlement in that area. “It appears that these people were visiting the lake for water resources and just to forage at the same time as the animals.”
A Green Arabia
The elephants, which had gone extinct in the neighboring Levant region about 400,000 years ago, would have been an appealing prey, and their presence also implies other ample freshwater resources and greenery.
Besides the footprints, some 233 fossils were unearthed, suggesting that carnivores were probably attracted to herbivores at Althar, similar to what is observed in African savannas today. According to the paper, fossils were first found for Homo sapiens outside of Africa between around 210and 180 thousand years in southern Greece and Levant.
The new research shows ‘inland routes, following lakes and rivers, may have been particularly important to humans dispersing out of Africa,’ too, said Stewart.
“The presence of large animals such as elephants and hippos, together with open grasslands and large water resources, may have made northern Arabia a particularly attractive place to humans moving between Africa and Eurasia,” added the paper’s senior author Michael Petraglia of the Max Planck Institute for the Science of Human History.