New research brings together 7,000 years of history in South Arabia to show how ancient pastoralists changed placement and construction of monuments over time in the face of environmental and cultural forces.
In a study published today (May 28, 2025) in PLOS One, an international team of archaeologists documents how monuments changed as the climate transitioned from a humid environment to, eventually, an arid desert.
Early monuments were built by larger groups at one time. But as people dispersed with the increasingly drier climate, smaller groups began constructing monuments and eventually built many of them in several visits.
"The findings show that monuments are a flexible technology that reflect the resilience of desert pastoralists in the face of a changing climate," said Joy McCorriston, lead author of the study and professor of anthropology at The Ohio State University.
But the key role that these monuments played in people's lives remained a constant.
"These monuments are touchstones for human social belonging," McCorriston said.
"As these groups became smaller and more spread out in the desert, people's interactions with the monuments consolidates a sense of being part of a larger society."
The research team analyzed 371 archaeological monuments in the arid Dhofar region of Oman. The earliest monuments studied were created from 7500 to 6200 BP (years Before Present) in the Holocene Humid Period. This period was characterized by higher-than-modern rainfall in southern Arabia.
The most recent monuments studied were created from 1100-750 BP, during the Late Antiquity when the area had become a desert.
While examples of most of the monuments and archaeological sites had previously been studied and classified, that research was generally very time- and place-specific, McCorriston said.
"What we've done is take a holistic look and show how all these individual monuments were part of a larger story of how the monuments changed as the lives of the people changed over thousands of years," she said.
The researchers did this by looking at a standard set of observations for all the monuments and developing a model that could be used in other contexts and places around the world.
For example, the model may be applicable and adaptable to assess social resilience in regions such as Saharan, Mongolian, or the high Andes.
One of the key measurements the researchers made was the volume and size of stones used in construction of the monuments. The earliest-built monuments in the study were Neolithic platforms, which contained larger stones. They were the largest monuments studied and were built at one time.
"The significance of the larger stones is that it takes more people to lift them. We know that it took at least seven strong men to lift the largest stones," McCorriston said.
"These large monuments that were built in one episode could only be built early on, before the region became arid. This is when large groups of people could still come together at one time."
Some of these larger monuments could serve large gatherings of people, where they could converge with multiple herds of cattle, and have animal sacrifices and feasts.
As the region became more arid and could no longer support large numbers of people nor their coming together, small groups traveled widely, going to where they could find water and places for their animals to graze.
They still had to build monuments in one episode, such as for burials, but by this time they tended to be smaller and use smaller stones, the researchers found.
What became more common were what are called accretive monuments, which people built over time - sometimes many years - rather than in one episode, like the earlier platform monuments.
One example of such monuments is accretive triliths. The higher number of triliths, along with the smaller stone volumes with few heavy stones, are consistent with monuments built over time by smaller, dispersed groups in an era of hyper-aridity.
These accretive monuments functioned as touchstones, allowing pastoralists to maintain connections and social resilience even as their movements and populations became more dispersed.
"In many cases, they were building a memory. They come to a monument and add their piece, which was a replicated element of the whole. It helped people maintain a community, even with those they may rarely see," she said.
It is impossible to say what were the precise messages the monuments were meant to convey, according to McCorriston. "What we can say is that the monuments conveyed readable meanings to others who shared the same cultural context."
It is possible, though, that some monuments were built to assure others in a social network access to important environmental information as they came by later.
"People would need to know, did it rain here last year? Did the goats eat all the grass? Pastoralists used this technology to help absorb the risk of being in an inherently variable and risky environment," she said. And they would need to depend on social networks for livestock exchanges, marriage partners, and rare materials, like sea shells, carnelian and agate and metal.
"That is one of the key points of what we found. Our model highlights a reliance on monuments to preserve connections and adapt socially in a changing world."
Other Ohio State co-authors on the study were Lawrence Ball, Ian Hamilton, Matthew Senn and Abigail Buffington. Other co-authors were Michael Harrower of Johns Hopkins University; Sarah Ivory of Penn State University; Tara Steimer-Herbet of the Université de Genève, Geneva, Switzerland; and 'Ali Ahmad Al-Kathiri and 'Ali Musalam Al-Mahri of the Ministry of Heritage and Tourism, Salalah, Sultanate of Oman.
