Scientists have revealed what they believe to be the earliest human footprints in the Arabian Peninsula, a crossroads of the world that plays a key role in understanding how humans left their African homeland and began to colonize the world. Along with the prehistoric human footprints, the team also discovered the tracks of elephants, hippos, and camels, giving a rare glimpse into the ecosystem at this unique time.
The groundbreaking study appears today in the journal Science Advances.
The fossilized footprints of Homo sapiens, aka humans, were discovered in an ancient lake deposit found in Saudi Arabia's Nefud Desert and studied by a team from the Max Planck Institutes for Chemical Ecology and the Science of Human History. A total of 376 tracks, including that of 7 hominin, 44 elephant, and 107 camel footprints, were found. At the ripe old age of roughly 120,000 years, these fossils currently appear to be the oldest human footprints outside of Africa.
"We argue for various reasons that these footprints were most likely made by Homo sapiens, which would make them the oldest human footprints outside Africa," Mathew Stewart, lead study author from the Extreme Events Research Group at the Max Planck Institute for Chemical Ecology, told IFLScience.
"There are other hominin footprints sites that date to earlier periods, but these are typically attributed to other hominin species such as Neanderthals," he added.
"We know that humans were dispersing out of Africa around 120,000 years ago, and that Neanderthals were absent from the region until the arrival of cooler conditions tens of thousands of years later. Therefore, we argue that the footprints were most likely generated by Homo sapiens."
It’s important to note the journey out of Africa wasn’t simply a single band of renegade early humans who left their homeland in a well-orchestrated continent hop. In reality, the migration was a complex affair with multiple waves of countless groups, all taking different routes with different intentions. Many of these early waves of human migration also reached dead ends, retreated, or died out. Neanderthals and other hominin species managed to migrate out of Africa long before Homo sapiens did.
The huge majority of these events, unfortunately, have not been immortalized in fossils or the geological record. Luckily, these newly discovered footprints managed to make it through the ravages of time and are now providing a rare snapshot of this crucial period in the history of humans and our planet.
"The present study... is unique in that it provides a snapshot in geological time. Unlike most other records – for example, the stone tool or fossil record – the study of footprints can provide extremely high-resolution information, in the order of hours or days," added Stewart.
It’s easy to imagine that the Arabian Peninsula has always been the hyper-arid desert it is today, but the area has undergone periods when it was actually a lush green land, filled with grasslands and vegetation. One of these periods was around 120,000 years ago during the last interglacial, a time when this slice of the world had relatively humid conditions. The researchers argue that appreciating this is key to understanding this discovery and why Homo sapiens along with other animals made a presence in the Arabian Peninsula at this time.
For starters, the presence of animal footprints, including elephants, hippos, and horses, highlights that this was a different ecosystem compared to today. It also seems no coincidence that many footprints of many animal species, including humans, were located around this once freshwater lake. Perhaps, the researchers argue, this lake once served as a vital safe haven for travelers who were suddenly finding that this lush land was being encroached upon by increasingly dry conditions and shrinking water supplies.
"At certain times much of Arabia's deserts were transformed into open grasslands with permanent lakes and rivers, similar to the savannas of East Africa today," the researchers said.
"Based on the lake sediments, and the dense congregation of human and animal footprints, it appears that the lake, at that time, was drying up, perhaps related to the arrival of the dry season. Therefore, it's possible that animals, and perhaps humans, were congregating around the lake in response to the arrival of the dry season and diminishing water supplies," Stewart explained.