Strontium isotope evidence for long-distance immigration into the Byzantine port city of Aila, modern Aqaba, Jordan

The ancient Red Sea maritime port of Aila was a major economic and manufacturing center during the 1st century B.C. through the Islamic era. The increased importance of Red Sea trade in the 4th century A.D. in addition to the arrival of a Roman legion in Aila also would suggest an increase in civilian residents arriving in the city for largely economic reasons. Strontium isotope analysis is used to identify any non-locally-born individuals within two mid-4th to early - 5th century A.D. cemeteries in the city (total N = 46). However, this assessment of population mobility requires an accurate estimate of the “local” strontium isotope value at Aila, a calculation made difficult through extensive food importation that occurred in this oasis city. Local faunal values combined with archaeological and historical evidence of local food production and food importation and childhood dietary practices were used to contextualize the human values within the Aila sample subjected to isotope analysis (N = 22). These sources suggest that the local signature of Aila ranges between 87Sr/86Sr = 0.7076142–0.708643, and only four individuals within the cemeteries were local to Aila. Most of the other individuals had 87Sr/86Sr > 0.7100, values unmatched in studies of bioavailable strontium in the Levant, Turkey, Egypt, Iraq, and the Persian Gulf. The lack of strontium dietary sources in southwestern Asia mirroring this signature suggests that many people buried at Aila hailed from great distances, supporting Aila’s role as a major trade center during the Byzantine period.