The path of life in the Arabian desert may have been paved with the dead.
In what is now Saudi Arabia, archaeologists have discovered a stunning network of lost roads, marked by human graves, connecting one oasis to another.
Thousands of years ago, these roads guided Bedouins and their livestock to access water through the roads marked by the graves of their ancestors.
The funerary avenues were the main transport network at the time, suggesting that 4,500 years ago, the people living in the Arabian Peninsula were much more socially and economically connected than we previously thought.
Stone burial chambers like those found in Saudi Arabia are common throughout the Arabian Peninsula, but in northwestern Arabia they are much more concentrated.
Over the past decade, satellite imagery has revealed thousands of pendant-like stone tombs in a region of the Arabian Peninsula that are either located on either side of or pointing at ancient roads in the desert.
As shown in the following figure.
On the left, you can see a series of circular stone tombs with tail "pendant" structures that border an ancient road.
On the right is the sparse terrain of stone tombs, all parallel to the road and leading to the water source.
The closer the road is to the oasis, the more concentrated the surrounding buildings.
Through satellite image comparisons and fieldwork, archaeologists working in Saudi Arabia determined that "the density of prehistoric tombs is incredible" and that "there is nothing similar elsewhere."
In one place called Haibar alone, researchers counted nearly 10,000 stone burial buildings, most of which are located near permanent water sources.
"These oases, especially Haibal, display some of the densest concentrations of tombs known in the world.
"The sheer number of tombs built around them suggests that at this time people had begun to settle permanently in these favourable sites."
Taking a closer look at individual oases, the researchers found a network of smaller paths radiating outward. They suspect these may be used to migrate fauna during rainfall seasons.
However, during droughts, roads that are longer distances may be more useful. By transferring water from one oasis or desert to another, the ancient Bedouins could travel through larger areas in search of better land and climate.
In fact, approximately 530 kilometres can be crossed through the identified network of funerary passages alone.