Excerpt from the linked summary^1 by study^2 co-authors Melissa Kennedy and Hugh Thomas:

>In the 1970s, the first archaeological surveys of northwest Saudi Arabia identified an ancient and mysterious rectangular structure.

>The sandstone walls of the structure were 95m long, and although it was determined to be unique, no further study of this unusual site was undertaken.

>These structures are now known as mustatils (Arabic for rectangle).

>In 2019–2020, we undertook excavations at a mustatil site called IDIHA-0008222. The structure, made from unworked sandstone, measures 140m in length and 20m in width.

>Excavations in the head of the mustatil revealed a semi-subterranean chamber. Within this chamber were three large, vertical stones.

>We have interpreted these as “betyls”, or sacred standing stones which represented unknown ancient deities.

> 

>Surrounding these stones were well-preserved cattle, goat, and gazelle horns. The horns are so well preserved that much of what we find is the horn sheath, made of keratin – the same substance as hair and nails.

>We found only the upper cranial elements of these animals: the teeth, skulls, and horns. This suggests a clear and specific choice of offerings.

>Further analysis suggests the bulk of these remains belonged to male animals and the cattle were aged between 2 and 12 years. Their slaughter would have formed a significant proportion of a community’s wealth, indicating these were high-value offerings.

>While recording these structures after rain, we noted that almost all mustatils pointed towards areas that held water.

>Current evidence suggests that the mustatils were in use between 5300 and 4900 BCE, a time when Arabia was green and humid.

>However, within a few generations, the ancient inhabitants of Saudi Arabia began to reuse these structures, this time to bury human body parts.

^1 Enigmatic ruins across Arabia hosted ancient ritual sacrifices, Melissa Kennedy and Hugh Thomas, 16 Mar. 2023, https://theconversation.com/enigmatic-ruins-across-arabia-hosted-ancient-ritual-sacrifices-201574

^2 Kennedy M, Strolin L, McMahon J, Franklin D, Flavel A, et al. (2023) Cult, herding, and ‘pilgrimage’ in the Late Neolithic of north-west Arabia: Excavations at a mustatil east of AlUla. PLOS ONE 18(3): e0281904. https://doi.org/10.1371/journal.pone.0281904