Petraglia has led expeditions into the Nefud for about 15 years to investigate hundreds of ancient lakes identified from satellite photographs that are now dry but which were important watering holes in the distant past.
The hard-packed clay lakebed among the sand dunes and the rocky ridges of the western Nefud – dubbed Alathar, which means “the trace” in Arabic – is the first place his team has found footprints of any kind.
The discovery of at least seven human footprints among the tracks of ancient elephants, camels, buffalo, equids (early ancestors of the horse), and antelopes at the site was astonishing, Petraglia said.
“We never imagined we’d find them,” he added.
Analysis of the footprints using a dating technique called optically stimulated luminescence, which measures the light given off by grains of quartz in the clay, indicates the human footprints must have been made by early Homo sapiens.
Although archaeological evidence shows some groups of the ancient human species Homo neanderthalensis – Neanderthals – entered what is now the Middle East up to 50,000 years ago, the footprints were at least 50,000 years too early and too far south to have been made by them, Petraglia said.
Their research also showed the shape of the footprints best matched early Homo sapiens, rather than Neanderthals or people living today, he said.
The researchers think the ancient humans were hunting prey animals, such as elephants and buffaloes, that had gathered at the lake to get water, he said.
They’ve found more than 300 animal tracks and 200 animal fossils at the site, and one group of human footprints – possibly from a hunting party – could show two or three individuals traveling together.
The location of the discovery strengthens the idea that some early Homo sapiens followed animal herds from the Sahara, across the Sinai Peninsula and into Arabia, rather than taking a “coastal route” beside the Mediterranean or a southern land bridge between Africa and Arabia.