Thousands of medieval Islamic tombs in eastern Sudan were arranged in hard-to-detect patterns, with sacred "parent" tombs hosting subclusters of emanating burials, according to archaeologists who studied the funerary monuments with a method designed for cosmology.
The team used satellite imagery to identify the locations of more than 10,000 monuments in the Kassala region of eastern Sudan. The monuments include tumuli, which are made of stone and are "relatively simple raised structures, widespread throughout African prehistory and history," and "qubbas," which is a term that referred to Islamic tombs and shrines in the pan-Arab world, a team of researchers wrote in a paper published July 7 in the journal PLOS One.
After the team mapped the funerary monuments, they had trouble interpreting the data, given that few of the monuments had been excavated.
"We faced the challenge of interpreting the creation of the funerary landscape with almost no traditional archaeological data, but [we had] a large enough data set to be able to hypothesize the presence of complex processes both at regional and local scale[s]," Stefano Costanzo, a doctoral student in archaeology at the University of Naples L'Orientale in Italy and lead author of the journal article, told Live Science.
"To the naked eye, it was clear that the clustered tombs were conditioned by the environment, but deeper meaning may have been implied in their spatial arrangement," Costanzo said.
He and other members of the team searched for statistical modeling techniques that could help them detect patterns. Ultimately, they decided on a method called the Neyman-Scott cluster process, which was originally developed to study the spatial patterns of stars and galaxies. As far as the team knows, archaeologists have never used the technique.
"The biggest feature of this model lies in the fact that it can deal with archaeological data sets that [lack excavation data and historical records] but are composed of a very large number of elements, which is the basis to meaningful statistical analyses," Costanzo said.
The modeling technique revealed that the Islamic tombs "were hiding several subclusters revolving around unidentifiable 'parent' tombs that acted as centers of attraction for subsequent burials, seemingly driven by general sacredness of the location and social trajectories of still existing mobile groups," said Constanzo.
The study also confirmed that areas where building material was readily available also tended to have more tombs and that environmental factors, such as the topography of the landscape, could also affect where tombs are located.
The Kassala region is inhabited by the Beja people, many of whom still live a semi-nomadic lifestyle, the team said in the journal article.
"The local clusters are most probably tribal/family cemeteries of the Beja people," the team wrote in the article. More research is needed to determine the precise locations of the "parent" tombs. Further research could also reveal who was buried in these parent tombs and what made them so special.
Interesting archaeological method
Scholars not affiliated with the research said the team's methods and findings were interesting.
"The approach is well suited to the investigation of nomadic groups, which range over vast territories," said Derek Welsby, an assistant keeper (similar to a curator) at the British Museum who has done extensive archaeological research in Sudan. The research should make future excavations in the area easier said Welsby.
The cosmological technique the team used "looks like quite an interesting and potentially valuable addition to archaeology's already quite large arsenal of statistical methods for gaining insights into the development of landscapes like these," said David Wheatley, an archaeology professor at the University of Southampton in the United Kingdom.
It also provides information on the history of the people who live there. "It provides quantitative support for the deep history of the Beja people," said Giovanni Ruffini, a history professor at Fairfield University in Connecticut.
"Modern scholars have relied on scattered references in literary texts to write Beja history, and the results just aren't satisfying," said Ruffini, who has conducted extensive research into medieval Sudan.
One scholar did suggest one limitation of the study, however.
Philip Riris, a lecturer in archaeological and paleoenvironmental modeling at Bournemouth University in the United Kingdom, expressed concern that the team included tombs from vastly different time periods in the same model. This "is risky because different funerary traditions are all thrown together," Riris said.