Dietary changes across time: Studying the indigenous period of La Gomera using δ¹³C and δ¹⁵N stable isotope analysis and radiocarbon dating

Abstract

Objectives This article presents new radiocarbon and isotopic data to provide further information about the diet of the indigenous population of La Gomera and its possible changes across time. Materials and methods δ13C and δ15N of 53 human and 19 faunal samples from different sites on the island have been obtained and analyzed. Of these, 52 have been radiocarbon dated to provide insight on chronological changes. Results Human dates range from the 3rd to 15th centuries AD, while faunal dates range from the 1st to 17th centuries AD. Stable carbon and nitrogen values are significantly different between the human and goat samples and have also a trophic increase of 3.4‰. Although male and female δ15N data are not significantly different. Both δ13C and δ15N values of both human and animal samples tend to discretely decrease over time. Discussion Radiocarbon dates from humans correlate with other dates obtained in the rest of the archipelago. Animal radiocarbon dates generally coincide except for one date, which requires further study. Isotopic δ15N data suggest a mix of marine and terrestrial protein consumption in humans, the latter being more abundant given the seasonality of the first. δ13C data also suggest a possible mixed diet in humans, with a predominance of C3 plants, like Hordeum vulgare, the only grain found in archaeological sites so far. Variations of both δ13C and δ15N over time suggest a slight modification on the diet, which could be related to environmental changes.

The early lives of the islanders: Stable isotope analysis of incremental dentine collagen from the prehispanic period of the Canary Islands

“…The primary source of dietary protein has been suggested to be mainly terrestrial in the whole archipelago, except for the case of the site of La Lajura , in El Hierro Island (Arnay‐de‐la‐Rosa et al, 2010). Likewise, δ 13 C values are predominantly related to a C3 plant environment both in our sample and in all previous studies done in the archipelago (Arnay‐de‐la‐Rosa et al, 2009; 2010; 2011; Lécuyer et al, 2021; Sánchez‐Cañadillas et al, 2021; Tieszen et al, 1995). If the marine contribution to the diet was higher, it would be expected to find higher values in δ 13 C isotopes due to the marine carbon reservoir being added to the consumers' tissues, as is the case of isotopic studies done on islanders from the Pacific (Kinaston et al, 2014).…”

“…Furthermore, the indigenous population occupied the islands during more than 1000 years (Velasco‐Vázquez et al, 2019), and while their diet was likely based on the same resources, it probably was not homogeneous in the proportions of those resources. Small differences are expected to appear depending on islands (Arnay‐de‐la‐Rosa et al, 2010), time periods (Lécuyer et al, 2021; Sánchez‐Cañadillas et al, 2021), or even local differences on each island, as evidenced by this study. This study has focused on the later period, albeit with one sample belonging to a funerary context with a wide timeframe, that being GRAN‐02 ( Guayadeque ), the differences of this profile compared with GRAN‐01 ( El Metropole ) could be both related to local variations (terrestrial vs. mixed‐diet) and chronological variations (different centuries).…”

“…Both M1 and M2 samples display a wide range of δ 15 N values, being especially high in TENC‐03, TENC‐04 and GRAN‐01, two samples from the same cave of La Angostura , and the sample from El Metropole , whose δ 15 N values are our threshold for an observable amount of marine contribution in the diet. These δ 15 N values are higher than bone collagen values from coastal populations from Gran Canaria (Lécuyer et al, 2021) (Table S2), therefore, δ 15 N values above 12 δ 15 N‰ should be taken into account, since they are similar to individuals considered as having a noticeable marine intake in their diets from the Canary Islands (Sánchez‐Cañadillas et al, 2021). Further, δ 13 C values display a similar tendency on the whole dentine section (Figures 3, 4), which correlates with values of C3 plant consumers.…”

“…Previous palaeodietary studies using bone collagen δ 15 N and δ 13 C measurements show us that the inhabitants of the archipelago relied on a mixed diet where principal protein component was obtained from terrestrial sources, although it sometimes included some marine protein (Arnay‐de‐la‐Rosa et al, 2009; Velasco‐Vázquez, 1998; Velasco‐Vázquez et al, 1997). This slight increase in marine foods among certain groups depended on several factors, and studies have been conducted on dietary differences among islands (Arnay‐de‐la‐Rosa et al, 2010) and time periods (Lécuyer et al, 2021; Sánchez‐Cañadillas et al, 2021).…”

Dating prehispanic and colonial sites on the island of Gran Canaria: a proposal for a radiocarbon hygiene protocol

“…For samples displaying evidence of a marine diet, both the diet correction and the reservoir effect should be applied prior to calibration. In this regard, a recent study on stable isotopes for the island of La Gomera has identified a human dietary evolution whose first stage principal contribution was marine (Sánchez-Cañadillas et al, 2021).…”