Urine salts elucidate Early Neolithic animal management at Aşıklı Höyük, Turkey

Abstract

The process of sheep and goat (caprine) domestication began by 9000 to 8000 BCE in Southwest Asia. The early Neolithic site at Aşıklı Höyük in central Turkey preserves early archaeological evidence of this transformation, such as culling by age and sex and use of enclosures inside the settlement. People's strategies for managing caprines evolved at this site over a period of 1000 years, but changes in the scale of the practices are difficult to measure. Dung and midden layers at Aşıklı Höyük are highly enriched in soluble sodium, chlorine, nitrate, and nitrate-nitrogen isotope values, a pattern we attribute largely to urination by humans and animals onto the site. Here, we present an innovative mass balance approach to interpreting these unusual geochemical patterns that allows us to quantify the increase in caprine management over a ~1000-year period, an approach that should be applicable to other arid land tells.

Fig. 1. Map of Aşıklı Höyük excavation.

Map showing excavation areas and sampling locations at Aşıklı Höyük. Three areas of sampling mentioned in the text (light gray areas) include area 4GH, area 2JK, or the west wall, and southern transect. Modified from Quade et al. (8).

Fig. 2. Secondary salts and mineral nodules in the micromorphology samples.

(A) Photomicrograph of the contact between a layer of intact dung and the underlying sediment. The dung layer contains thin, undulating lenses of calcareous spherulites (S) interbedded with siliceous phytoliths (p). The sediment beneath contains fragments of volcanic glass (v), degraded organic material (om), and secondary nodules of apatite (a) in a matrix rich in wood ashes and clay minerals. A concentration of secondary mineral crystals—unidentified but likely soluble salts—formed within a void is indicated with an arrow. Plane-polarized light. (B) Same view as (A), cross-polarized light. Area scanned using micro–x-ray fluorescence indicated with the red box. (C) Elemental distribution map showing enrichment of sodium in the secondary mineral crystals, as well as phosphorus in the apatite and organic material, potassium in the volcanic glass, and aluminum in the clay-rich matrix. Note that although concentrations of suspected soluble salts (as well as other secondary minerals such as apatite and gypsum) have been observed in the micromorphology samples, further identification is limited because of highly variable crystal morphologies (58).

Fig. 3. Stratigraphic profile and soluble salt concentrations from area 4GH (see Fig. 1 for location) at Aşıklı Höyük.

(Left) Depth profile of the archaeological material and basal sediments, with specific major archaeological Levels 5 to 3 indicated. Alternating silt and sand represented by patterns on stratigraphic column, while grain size is shown through relative width of each section. (Right) Concentrations of seven soluble salts (see key) versus depth. The black curve denotes the average (Avg.) of all salts.

Fig. 4. Comparison of soluble salt concentrations between archaeological and nonarchaeological sediments.

(A) [Na⁺], (B) [Cl⁻], and (C) [NO₃⁻] (in moles × 1000 kg⁻¹) across major archaeological intervals (levels 5 to 2). Natural alluvium soluble salt concentrations from (i) all samples and (ii) samples directly beneath level 5 in area 2JK are provided only for comparison. Whisker lengths depict one-third of the interquartile range. The solid line within each box represents the median, while the dashed line shows the mean of the sample set. Data displayed here include general midden, dung-dominated midden, and alleyway samples combined.

Fig. 5. δ¹⁵N values (in per mil) of refuse samples from Aşıklı Höyük compared to a range of sources of nitrates.

Whisker lengths denote one-third of the interquartile range. The solid line within each box represents the median, while the dashed line shows the mean of the sample set. Data not from Aşıklı Höyük are taken from (–43).

Fig. 6. Model-predicted densities (organisms per square meter) of organisms required to produce urine-related [Na⁺], [Cl⁻], and [NO₃⁻] found at Aşıklı Höyük, averaged across specific time intervals (levels 5 to 2).

(A) Assuming a constant sedimentation rate over the entire period of occupation and (B) using variable sedimentation rates based on carbon-14–dated level boundaries (8). Densities of ≤0 indicate that conservative estimates of other inherited, anthropogenic, and postdepositional sources of soluble salts account for total [Na⁺], [Cl⁻], and [NO₃⁻] observed in the refuse. (C) Relative abundance [percentage of the total number of identified skeletal specimens (NISP)] of caprines in the vertebrate faunal assemblages averaged by level [updated from (7) from Aşıklı Höyük].