Isotope analysis of Bronze Age El Algar sites in present-day south-eastern Spain provides a integrated picture of diets and farming strategies

The sampled human individuals showed no significant difference between isotope values for males and for females, suggesting that diets may have been similar between genders. However, "elite" individuals at La Bastida showed higher levels of both carbon and nitrogen. This might have implied that the people of La Bastida consumed higher levels of animal-based food, but the authors suggest that the isotope value differences between La Bastida and Gatas could in fact have resulted from similar dietary compositions. Nitrogen values are similar at both sites for barley, but higher for the domestic animals at La Bastida, meaning that diets with similar relative contributions of barley and meat/dairy products would have led to higher nitrogen values in the humans at La Bastida compared to Gatas.

The researchers found a strong reliance on cereal farming, supplemented by livestock, in the El Algar economy. The range and values of carbon in the barley and wheat sample reflect what was likely a dry, unirrigated landscape, though nitrogen levels in the cereal crops suggest the El Algar people applied animal manure to their fields. Cereals and their by-products appear to have contributed substantially to the forage of domesticated sheep/goats, cattle and pigs.

Fig 1. Maximum territorial extension of the El Argar culture and locations of the analysed sites of La Bastida and Gatas.
Fig 1. Maximum territorial extension of the El Argar culture and locations of the analysed sites of La Bastida and Gatas. - Other sites with isotopic analyses of human remains: 1. Cerro de la Virgen, 2. Cuesta del Negro, 3. Baeza, 4. Úbeda, 5. Los Millares, 6. La Navilla. © ASOME, UAB

Corina Knipper, Cristina Rihuete-Herrada, Jordi Voltas, Petra Held, Vicente Lull, Rafael Micó, Roberto Risch, Kurt W. Alt. Reconstructing Bronze Age diets and farming strategies at the early Bronze Age sites of La Bastida and Gatas (southeast Iberia) using stable isotope analysisPLOS ONE, 2020; 15 (3): e0229398

DOI: 10.1371/journal.pone.0229398

The El Argar society of the Bronze Age in the southeast of the Iberian Peninsula (2200–1550 cal BCE) was among the first complex societies in Europe. Its economy was based on cereal cultivation and metallurgy, it was organized hierarchically, and successively expanded its territory. Most of the monumentally fortified settlements lay on steeply sloped mountains, separated by fertile plains, and allowed optimal control of the area. Here, we explore El Argar human diets, animal husbandry strategies, and food webs using stable carbon and nitrogen isotope analysis of charred cereal grains as well as human and animal bone collagen. The sample comprised 75 human individuals from the sites of La Bastida (n = 52) and Gatas (n = 23), 32 domesticated and wild animals as well as 76 barley and 29 wheat grains from two chronological phases of a total time span of ca. 650 years. The grains indicate extensive cereal cultivation under rain-fed conditions with little to moderate application of manure. Especially at La Bastida, crops and their by-products contributed significantly to the forage of the domesticated animals, which attests to a strong interrelation of cultivation and animal husbandry. Trophic level spacing and Bayesian modelling confirm that human diets were largely based on barley with some contribution of meat or dairy products. A cross-sectional analysis of bone collagen suggests that children were breastfed until about 1.5–2 years old, and infants from Gatas may have suffered from more metabolic stress than those at La Bastida. Adults of both sexes consumed similar diets that reflect social and chronological variation to some extent. Despite significantly higher δ13C and δ15N values at La Bastida than at Gatas, the isotopic data of the staple crops and domestic animals from both sites indicate that such differences do not necessarily correspond to different average human diets, but to agricultural strategies. These results urge for a reassessment of previous isotope studies in which only human remains have been taken into account. The study highlights that disentangling the complex influences on human isotope compositions requires a firm set of comparative data.