The details of this paper have been recently published in an article titled "Archaeologists Find Prehistoric Cultic Monuments in Saudi Arabia" by Ruth Schuster in Haaretz.com

Description of mustatils

Called mustatils, based on the Arabic word for "rectangle", these structures were built between 8,500 to 4,800 years ago. This period is known as the Middle Holocene, writes Hugh Thomas of the University of Western Australia and colleagues in Antiquity.

Mustatils in northwest Saudi Arabia

Rectangular, with a head and base, and elongated sides, some of the mustatils had an entrance at the base and a chamber smack in the centre of the head, while some had multiple chambers at the head. Also some had orthostats, large stone blocks which are taller than they are wide, write Thomas and colleagues.

Ranging in size from titches a mere 15 meters long to monsters more than 620 meters in length, these structures are found all over the peninsula, including on the slopes of volcanoes. They are made using simple dry-stone masonry - unworked flat slabs of sandstone or other local rocks. Some mustatils have dividing walls down their length.

Earlier theories

Suggestions, regarding what these mustatils were, ranged from a pen or trap for animals, which would be caught within the walled structure from which they couldn't escape; burial sites; and/or territorial markers.

Distribution of mustatils in northwest Arabian peninsula

As to being a trap, the walls of the mustatils were too low to prevent the more agile of the herbivores from jumping out and fleeing, observed Thomas and the team. Also, proving contrary to this simple use, the mustatils are architecturally more complex than had been initially realized.

In their paper, Thomas and team focus on a subset of over 1,000 mustatils in northwest Saudi Arabia, a type dubbed "gates." In order to get a potential insight into the logic underlying their construction, requires understanding of the conditions prevailing in the Neolithic peninsula.

Green Arabia

Some had thought that Arabia was bereft of life other than lizards until the Iron Age but now it turns out that the peninsula hosted a number of prehistoric activity, certainly in the early Holocene. This makes one realise that the Arabia peninsula in the early Holocene, was green.

"Green Arabia" and the potential role of the mustatils has been previously described. Roughly 10,000 years ago, the peninsula was lush with grasslands reaching their maximal expansion perhaps 8,000 years ago, and that is the very time many mustatils were being erected. It is from that time, the process of aridification was rapid, replacing the green grassland with hardier shrubs.

Huw Groucutt of Germany's Max Planck human history group described the mustatils in a 2019 paper in the journal The Holocene as "fence-like" low walls created by piling up stones and dated one of the structures to 7,000 years ago. It was postulated by this team that the mustatils were somehow related to ancient rituals in the context of the transition from hunting and gathering to pastoralism and the resulting territoriality in the "challenging environments" of northern Arabia.

In the new paper, Thomas and the team focus on the "gate" mustatils in northwestern Saudi Arabia. Many of these "gates" have entrances positioned at the centre of their base, directly opposite the "head" of the mustatil at the other end. There were chambers at the heads of some, with doorways to the main courtyard. At times the doorways seem to have been deliberately blocked, casually or decisively, which could argue that the facility had been "decommissioned."

It was found that in some cases the interior chamber was apparently roofed by a single huge rock, aka a capstone. The main "courtyard" of the mustatil was generally empty, or at least it is now yet some, the features niches in the walls.

The team mentions that in their interior, smack in front of the base, many mustatils featured three to eight separate or interlocking circular cells, more or less identical in size. These cells were built along the base, leaving a passage between the outer edge of the base and the cells, leading to the entrance to the courtyard.

Archaeologists noticed strange structures shaped like the serifed capital letter I, often in association with the rectangular mustatils which in contrast were low rubble-filled platforms. Of the 131 such I-shaped platforms recorded by the AAKSA project, 73 were in association with mustatils - as many as six per mustatil. Apparently contemporary with the mustatils and likely used together. But for what?

Whispers of animal sacrifices

In these mustatils, archaeologists have been finding evidence whispering of ancient animal sacrifices, possibly to the spirits, gods or ancestors.

For instance take the Aerial Archaeology in the Kingdom of Saudi Arabia excavation of an undisturbed mustatil east of AlUla. Bones were found, mainly of cattle but also of sheep, goats and gazelle, in the central chamber of the head. Radiocarbon dating of these placed them to the sixth millennium B.C.E., not all that long after the animals' domestication.

'Simple' mustatil, 'complex' mustatils, single (B) and double (C)

By the time the mustatils and the I-shaped structures were erected in the Saudi non-desert, the bovine, the ovine and the caprine were tamed. As no evidence of human habitation was found in the mustatils; the archaeologists choose to interpret the bones as remains from offerings.

The evidence found so far all lead to the surmise that the mustatils served a ritual function for a cattle-oriented cult. These discrete structures, prominent in the landscape were built during a period of climatic insecurity, featuring elements such as orthostats and circular interior chambers but not bedding or anything smacking of human habitation and comfort; the walls were generally too low to keep quadrupeds penned inside; and Thomas and the team see in their collective minds' eye - the passageways were too narrow to enable people to walk side by side. They had to be walking in procession from the entrance at the rear to the structure's head.

The indirect evidence of a Neolithic cattle cult in northwestern Arabia is rock-art. These feature scenes of hunting and cattle herding, showing how different environmental conditions were back then. Maria Guagnin, Groucutt and others in 2015 wrote that art in over 250 panels in Shuwaymis "provide compelling evidence that humans and animals once thrived in landscapes that are extremely arid today".

Guagnin and her team showed that earlier peninsula rock art shows hunting, while the later drawings show cattle herding. Interestingly, the cattle scenes were often engraved over, or integrated into, older hunting scenes.

They wrote that hunters turned into herders and it is possible that the mustatils went up to exhort the powers to restore the good times, when the desert was green.