Today, Jordan Rift Valley east of the Mediterranean is challengingly parched, bare and uneven in its terrain. Not the easiest place to take a hike, let alone traverse with your entire family on foot.
But research suggests back when humans first migrated out of Africa this was likely the route they chose.
"The presently harsh environment of the Levant and Arabia are the key regions through which members of the genus Homo, including our species Homo sapiens, had to pass through when leaving Africa and moving into Eurasia," explains archeologist Michael Petraglia from Griffith University in Australia.
While this stretch of land is the only permanent land bridge, researchers are open to the possibility that our ancient relatives exited Africa via what is now the Red Sea, with water levels lower during the glacial periods and the climates on both banks far kinder.
So Shantou University geochronologist Mahmoud Abbas and team examined thirteen 84,000 year-old sediment samples across several Rift Valley sites. Stone tools at one site revealed hominins maye have at least attempted this pathway. Other studies have also found artifacts, footprints, and human fossils from caves nearby dating to the same period.
The sediments also revealed a very different landscape at the time. Layers of sand and gravel were interrupted by rich organic matter and mud containing root casts, suggesting rich vegetation.
This sharp change indicates increased rainfall that turned the region into a series of wetlands amidst a wider arid zone during this period, providing the perfect opportunity for mammals – including humans – to expand their territory.
"Rather than dry desert, savannah grasslands would have provided the much-needed resources for humans to survive during their journey out of Africa and into southwest Asia and beyond," explains Abbas.
"The Levant acted as a well-watered corridor for modern humans to disperse out of Africa during the last interglacial, and we have now demonstrated this is the case in the Jordan Rift Valley zone."
Humans dispersed from Africa to Eurasia several times during the Mid to Late Pleistocene, 129 to 71 thousand years ago, and not all of their attempts were successful. But at least some who likely took this journey through the Jordan Rift Valley likely became ancestors of those of us with European and Asian heritage.
This research was published in Science Advances.