Stable isotopes of archaeological and modern semi-terrestrial crabs (Potamon potamios) provide paleoecological insights into brachyuran ecology and human resource acquisition in late Holocene Jordan

Abstract

Archaeological remains of brachyurans (e.g. crabs) are often overlooked as potential paleoenvironmental and paleoclimatical proxies in contrast to other marine and terrestrial invertebrates such as mollusks and landsnails. The potential for fine-scale regional paleoclimate reconstruction based upon these organisms' behavioral ecology has yet to be examined. We present novel isotopic analyses of the remains of a semiterrestrial freshwater crab (Potamon potamios) endemic to southwest Asia recovered from the archaeological site of Khirbat al-Mudayna al-’Aliya (KMA). KMA lies on a southern tributary of the Wadi al-Mujib in the Hashemite Kingdom of Jordan, approximately 40 km east of the Dead Sea. Excavations here recovered architecture, artifacts, and ecofacts dating to a single-period occupation during the early Iron Age (∼1000 cal BCE). Oxygen and carbon isotopes from these brachyuran remains were analyzed in conjunction with a two-year isotopic and morphometric study of the modern potomonautid population near the archaeological site and at nearby wadi systems to assess whether the isotopic values of modern crab populations correlated with variables such as temperature, including isotopic study of the pools in which crabs were found. In turn, these data could be used to reconstruct paleoclimate or paleoenvironment in the archaeological population. The high correlation in oxygen isotope values between crab carapaces and the water of the pools in which they were sampled suggest that variability in isotopic values of crab specimens recovered from KMA is tracking ancient human capture of these organisms across potentially different pools. Further, intra-year variability in isotopic values in modern crab carapaces as well as the similarity of isotopic values across wadi systems with different environments suggest that P. potamios remains cannot be used as reliable paleoenvironmental indicators. The implications of this research will have significance for archaeologists and other researchers in the study of paleoenvironment and paleoecology, and bears upon human mobility, resource acquisition, and human-nonhuman animal relationships.