How migration in search of water shaped Arabia over 10,000 years

Populations in the drier southern areas had to flee to the coast, in what is now the UAE and Oman, during droughts

Jubbah Oasis pictured today, with modern farming on the desert floor. In the past, this area would have been a wetland and lake region. Courtesy: Palaeodeserts Project.

Water scarcity has long been a central issue in Arabia, and now research has demonstrated just how pivotal a role it played in shaping where and how people lived over the past 10,000 years.

A study revealed a stark contrast between northern Arabia, where populations could survive during arid times thanks to inland water resources, and the peninsula’s southeast, where people had to flee to the coast at times of drought.

It has also highlighted art on boulders, well-preserved hearths and expertly made stone tools – painting a vivid picture of ancient survival in one of the world’s harshest environments.

“The people of Arabia have had to learn to cope with an environment that was wet and had more rainfall, versus an environment that got drier during long intervals,” said the lead author of the study, Prof Michael Petraglia, of the Max Planck Institute for the Science of Human History in Germany.

The findings are the product of a decade of twice-yearly field trips to desert sites by a multinational team of researchers. While southeastern Arabia, including what is now the UAE and Oman, has been extensively studied by archaeologists, there had been fewer excavations in the northern part of the peninsula.

Geological analysis indicates that rain increased in Arabia from about 10,000 years ago, creating many lakes scattered across the peninsula, but subsequent fluctuations meant that these came and went.

Dry periods could last centuries, such as one that stretched from 7,500 to 7,200 years ago, and another from 6,500 to 6,300 years before present.

One of the most notorious arid spells was the “Dark Millennium”, a time of great hardship that began about 5,900 years ago and lasted for eight centuries.

Yet, excavations have shown that some populations remained inland in northern Arabia even at times of drought because there were deep aquifers and seasonal lakes that could be exploited.

“People were coalescing around oases and tapping into the water table,” said Prof Petraglia.

A key part of the research, published this year in the American journal the Proceedings of the National Academy of Sciences, involved analysing satellite images, which revealed as many as 10,000 ancient lakes in Arabia.

The 'palaeolakes' leave behind lake plains – the former lake bottom – and ancient shorelines that can be distinguished from surrounding ecology or vegetation.

The researchers “ground truthed” their maps, travelling by four-wheel drive and helicopter to isolated desert areas to find if there really had been lakes in the areas indicated by satellite images.

Visiting about 200 locations, they looked for lake deposits, such as muds and ancient clays, and freshwater shells, and found that their data was about 90 per cent accurate.

The presence of artefacts like hand axes and hearths, underground pits later analysed with radiocarbon dating, indicated that seven out of 10 of the ancient lakes, many in the Nafud desert, were once inhabited.

“We found hearths that look like they were put out yesterday. They were beautifully preserved, but when we tested them, they were several thousand years old,” said Prof Petraglia.

“People have repeatedly occupied these areas when there was water. They came and went through time.”

The area has also yielded magnificent rock art, including petroglyphs carved into the rocks with hammers, and paintings created with red dyes. Depictions included camels with prominent ribs – thought to indicate animals starving during harsh dry periods.

Some of the wells still exist and are celebrated tourist sites, such as the large walled structure at Tayma in Saudi Arabia.

“People were coalescing around oases and tapping into the water table. Over the last 5,000 years people started to conserve surface water – they started to build dams and to excavate shallow wells,” said Prof Petraglia.

Further south, conditions during dry periods were even harsher: inland there was so little water and vegetation that the mobile populations of animal herders who had lived there were forced to relocate to the Arabian Gulf coast, including to areas that are now part of the UAE.

Excavations on the UAE’s Akab island, near Umm Al Quwain, have previously highlighted mounds of dugong bones from the Dark Millennium, which researchers suggest could reflect ritualised consumption.

Other previous studies, of burials from around the same time at Jebel Buhais, a mountain area in Sharjah, indicated that people were generally healthy, although some remains showed damage indicating violence.

Following the Dark Millennium, conditions improved and populations spread more widely, practising oasis agriculture and trading regionally.

Archaeologists say the history of climate-induced hardship and how it has shaped where people can live offers lessons as Arabia faces temperature increases in modern times.

Prof Petraglia said it indicates the importance of conserving underground water resources and of selecting the right crops and animals for harsh conditions.

“The past shows resilience to some of these climatic changes, but that some populations had a very hard time coping with these changes. We think some populations had to move or possibly died out,” he said.

“The past is really a lesson for us all; that climate really is quite significant and we need to take it seriously.”