In December 2023 through January 2024, research funded in part by an IASA Main Research Grant was undertaken to identify Wadi Suq-period (ca. 2000-1600 BCE) teeth from the Shimal Necropolis in the Emirate of Ras Al Khaimah for isotopic sampling. Here, three different isotopes (strontium, oxygen, and carbon) from human teeth provide insight into the complexity of responses to climate change at the end of the third millennium BCE in the UAE. These results were presented at the 2024 Seminar for Arabian Studies, and a manuscript based on this research has been submitted to the American Journal of Biological Anthropology.
The site of Shimal remained continuously occupied over some two thousand years despite intense aridification around 2200-2000 BCE that marked the beginning of the Wadi Suq. Elsewhere across southeastern Arabia, such aridification brought with it a growing inability to maintain oasis agriculture, leading to the decline or abandonment of settlements and a breakdown in interregional exchange systems. Unsurprisingly, a substantial shift in funerary rituals followed, with more variable mortuary structures now dominated by individual interments or, less frequently, collective graves containing fewer numbers of individuals than in the previous Umm an-Nar period (ca. 2700-2000 BCE). Consequently, the once-wide geographic distribution of Umm an-Nar sites and tombs across the region shrunk considerably, becoming concentrated most visibly in Ras Al Khaimah. Shimal is the largest in a series of expansive second millennium cemeteries in the northern emirates.
Prior isotopic research on human dental enamel from the tombs at Shimal included the Umm an-Nar tomb Unar 1 as well as Wadi Suq tombs SH 95 and SH 103. This study expanded sample sizes from both periods, adding individuals from tombs Unar 2, SH 99, and SH 602. Enamel samples from these teeth were later analyzed in Summer 2024 for strontium, oxygen, and carbon isotope values. Strontium isotope ratios from Umm an-Nar tombs Unar 1 and Unar 2 did not differ statistically from one another. However, Umm an Nar ratios were significantly different from their slightly higher Wadi Suq counterparts, despite almost all individuals from both periods possessing local ratios.
Also notable was a site-wide increase in oxygen isotope values over time, as lower values from tomb Unar 1 differed significantly from those individuals interred in Unar 2 and Wadi Suq tombs (Figure 1). Subsequently, the water source(s) used by those interred in Unar 2 appear more closely aligned with those used during the later Wadi Suq period. However, a broader regional perspective on human oxygen values revealed a more complicated picture, as Umm an-Nar tombs from Umm an-Nar Island, Tell Abraq, Mowaihat, all shared similar values to Unar 2 and the Shimal Wadi Suq tombs.
Figure 1. Scatterplot depicting strontium and oxygen isotope values from human dental
enamel for Umm an-Nar and Wadi Suq individuals at Shimal. (scatterplot: L. Gregoricka)
Stable carbon isotope values between Unar 1, Unar 2, and the four Wadi Suq tombs did not differ statistically from one another, indicating that diet did not change considerably over time at Shimal despite climate change. Nevertheless, when comparing the carbon isotope values of the Shimal individuals to Umm an-Nar communities residing closer to the coast, those from Shimal demonstrated significantly lower carbon isotope values and reduced dietary variability, indicating that people from Shimal relied more on C 3 -based terrestrial resources, whether related to oasis agriculture or pastoral practices.
Together, data from these three isotopes present a complex picture of the transition from the Umm an-Nar to the Wadi Suq. A significant increase in strontium isotope ratios over time, coupled with what we know about the lack of change in diet, indicates that at least some Wadi Suq individuals may have been interacting with slightly older geologic zones at young ages. This could be the result of community movement from elsewhere in southeastern Arabia northwards, perhaps in the form of climate refugees seeking out more permanent sources of ground water. This would be especially applicable to communities living in the interior of Oman in the foothills of the Hajar Mountains. This hypothesis is bolstered by the shift in oxygen isotope values over time, which could suggest that incoming groups may have initially consumed water from different sources in childhood before moving north, instead of prior interpretations of aridification driving changes to these values. Regardless, however, it should be stressed that because of relatively small sample sizes for the Wadi Suq period, all interpretations remain tentative, and more research is needed.
