Access to freshwater alone was not enough for prehistoric humans to permanently settle desert landscapes, according to a new study which suggests that suitable stone for making tools was an equally important resource.
Researchers found that parts of the Arabian Peninsula remained largely uninhabited even during wetter periods when lakes and grasslands transformed areas of desert into the environment known as “Green Arabia”.
The international study, published in Nature, challenges settlement models that primarily use water and climate to predict where prehistoric populations could have lived.
Instead, researchers argue that the availability of stone suitable for tool production needs to be considered alongside freshwater.
Water without stone
During wetter phases of the Pleistocene, increased monsoon rainfall repeatedly transformed parts of Arabia, creating lakes and grasslands across regions that are now extremely arid.
These environmental changes are thought to have opened routes into the Arabian interior for prehistoric populations.
However, the new research suggests that the presence of water did not necessarily make these landscapes suitable for permanent occupation.
Evidence came partly from an approximately 1,500-kilometre journey across the Rub’ al Khali desert in Saudi Arabia.
Researchers encountered numerous traces of ancient freshwater lakes but found no stone tools or suitable raw material for manufacturing them.
Stone suitable for tool production is exposed around the margins of the desert, while farther into the interior it disappears beneath extensive deposits of sand and salt flats.
“We stood on the shore of one ancient lake after another, yet found nothing made by human hands. Water without stone was a dead end,” said Rudolf Dellmour from the University of Vienna, lead author of the study.
Stone tools shaped where people could live
For prehistoric populations dependent on stone technology, access to suitable raw material was fundamental.
Stone was needed to manufacture cutting tools and other implements used for everyday activities, making reliable sources of workable material an important factor when choosing where to establish settlements.
The researchers suggest that areas containing freshwater but lacking accessible stone could therefore support only limited or temporary human activity.
This may explain why evidence of prehistoric occupation is concentrated in particular parts of Arabia despite the presence of ancient lakes elsewhere.
“Models built on climate and water alone can substantially overestimate how much of the desert prehistoric people were able to inhabit,” said Roman Garba from the Institutes of Archaeology of the Czech Academy of Sciences in Prague and Brno and the Nuclear Physics Institute of the CAS.
Evidence from Oman
Researchers also tested their hypothesis using archaeological evidence collected in Oman.
Data came partly from the Czech ARDUQ archaeological expedition, which conducted fieldwork between 2022 and 2025.
Observations documenting where suitable stone raw materials occur were compared with the distribution of known prehistoric archaeological sites.
Long-term archaeological research conducted by anthropologist Jeffrey Rose from the University of Algarve also provided an important dataset.
“Two decades of research in Oman taught us exactly where good stone is to be found. When we carry that knowledge over into the sand desert, the model predicts an empty interior – and that is precisely what our fieldwork confirmed,” said Rose.
The results indicate that prehistoric settlement patterns correspond more closely with landscapes where freshwater and suitable stone occurred together than with the distribution of water alone.
New model predicts prehistoric settlement
Based on the findings from Arabia, the researchers developed a model combining information about water availability with the geological distribution of stone suitable for tool production.
The system is designed to identify areas where populations dependent on stone tools could potentially have maintained permanent settlements.
Unlike models developed specifically for Arabia, the approach can be applied to arid landscapes elsewhere in the world by incorporating local geological and hydrological data.
The researchers have released the model as an open-source tool, allowing archaeologists to apply it to other regions and compare its predictions with archaeological evidence.
The underlying data and code have also been made publicly available.
The study suggests that reconstructing prehistoric population movements across deserts requires more than identifying where ancient rivers and lakes once existed.
For communities whose survival depended on stone technology, the presence of freshwater could make a landscape habitable – but without accessible raw material for tools, it may still have been unsuitable for permanent settlement.
Sources : Czech Academy of Sciences
