Tooth oxygen isotopes reveal Late Bronze Age origin of Mediterranean fish aquaculture and trade

Abstract

Past fish provenance, exploitation and trade patterns were studied by analyzing phosphate oxygen isotope compositions (δ¹⁸O_PO4) of gilthead seabream (Sparus aurata) tooth enameloid from archaeological sites across the southern Levant, spanning the entire Holocene. We report the earliest evidence for extensive fish exploitation from the hypersaline Bardawil lagoon on Egypt's northern Sinai coast, as indicated by distinctively high δ¹⁸O_PO4 values, which became abundant in the southern Levant, both along the coast and further inland, at least from the Late Bronze Age (3,550-3,200 BP). A period of global, postglacial sea-level stabilization triggered the formation of the Bardawil lagoon, which was intensively exploited and supported a widespread fish trade. This represents the earliest roots of marine proto-aquaculture in Late Holocene coastal domains of the Mediterranean. We demonstrate the potential of large-scale δ¹⁸O_PO4 analysis of fish teeth to reveal cultural phenomena in antiquity, providing unprecedented insights into past trade patterns.

Figure 1

A map of the Bardawil Lagoon of the northern Sinai coast – the main nursery of Sparus aurata in the southeast Mediterranean basin.

Figure 2

Map of archaeological sites in the southern Levant from the beginning of the Pre-Pottery Neolithic (PPN: ~9,700 years BCE) until the Byzantine period (BYZ: 300 to 600 CE), from which S. aurata remains were analysed for their phosphate oxygen isotope composition. Also indicated is the location of the hypersaline Bardawil lagoon along the north coast of Sinai, Egypt, which is the proposed source of S. aurata with high δ¹⁸O_PO4 values of >23.5‰.

Figure 3

Blue sinusoidal curves represent the seasonal range expected for fish bioapatite δ¹⁸O_PO4 values forming in isotope equilibrium with the water of the hypersaline Bardawil lagoon and southeast Mediterranean, respectively. For the Bardawil lagoon an average δ¹⁸O_SW of 3.7‰ and a water temperature range of 14 to 28 °C^,, and for the southeast Mediterranean an average δ¹⁸O_SW of 1.6‰ and a water temperature range of 15 to 30 °C^, were used. Teeth of modern S. aurata fall within the predicted δ¹⁸O_PO4 trend of their according habitat (data for Bardawil fish are from Kolodny et al.; data for southeast Mediterranean fish: Sisma-Ventura et al. (this study), reflecting the season of tooth formation. Note that molariform tooth crown mineralisation seems to have occurred year around. This reference frame was used to infer the habitat of ancient S. aurata.

Figure 4

Temporal evolution of phosphate oxygen isotope (δ¹⁸O_PO4) composition in archaeological Sparus aurata tooth enameloid and estimated body mass. (A) Box plots of δ¹⁸O_PO4 values of S. aurata from 12 different archaeological sites in the southern Levant (Fig. 2), spanning the time from the Pre-Pottery Neolithic until the Byzantine period (Table S1). Note, different width of the box plots reflects the age ranges of each site (see Table S1 for details). Changes of Eastern Mediterranean Sea level are taken from^,. The sea level stabilised at the present level (±1 m) about 1,600 years BCE, allowing the formation of the shallow, hypersaline Bardawil lagoon on the shallow shelf of the Sinai coast (Fig. 1). For comparison on the left y-axis the ranges of δ¹⁸O_PO4 values expected for S. aurata that formed their teeth in the Bardawil lagoon and in the southeast Mediterranean (Fig. 3) are given. (B) Box plots of estimated body mass of S. aurata. Tooth δ¹⁸O_PO4 of S. aurata increased to hypersaline values and at the same time fish body mass decreased significantly. Coloured horizontal boxes represent mean values and standard error of δ¹⁸O_PO4 and body mass of S. aurata from the PPN-EBA and LBA-BYZ time intervals.

Figure 5

Enameloid phosphate oxygen isotope composition (δ¹⁸O_PO4) of S. aurata teeth versus estimated fish body mass (inferred from molariform tooth size; see text for details) for two different time intervals: (A) Pre-Pottery Neolithic (PPN) to Early Bronze Age (EBA): 9,700 to 3,000 BCE. The stippled light blue line marks the lower threshold for unambiguous hypersaline δ¹⁸O_PO4 values of S. aurata from the Bardawil lagoon. Note that before the LBA the few Sparus with such high δ¹⁸O_PO4 values derive from other, now submerged hypersaline lagoons as the Bardawil lagoon was not present at this time; (B) Late Bronze Age (LBA) to Byzantine period (BYZ): 1,200 to 600 years BCE.

Figure 6

Comparison of δ¹⁸O_PO4 values from teeth-jaw pairs of S. aurata individuals from different archaeological time periods. Pre-Pottery Neolithic: PPN; Pottery Neolithic: PN, Chalcolithic: CAL, Bronze Age: BA, Iron Age: IRA, and Byzantine period: BYZ. Note that for the Byzantine period both bone and enameloid δ¹⁸O_PO4 values reflect hypersaline water, indicating that these fish lived their full life span in the Bardawil lagoon. Values lower than the southeast Mediterranean (southeast Mediterranean) range may reflect either fish migration into brackish lagoons or a certain degree of diagenetic alteration of the bone tissue in low δ¹⁸O_water. Overall, δ¹⁸O_PO4 values reflect the distinct salinity levels of the water bodies in which S. aurata mineralised their bones and teeth. The molariform tooth δ¹⁸O_PO4 values thus indicate in which setting they were caught.