ISÓTOPOS ESTÁVEIS (C/N) – LAPA DO SANTO

Carbon and nitrogen stable isotope analysis on bone collagen is widely used in archaeology for reconstructing ancient diets. A total of 17 human bones and 51 faunal bones from the early Holocene deposits of Lapa do Santo were analysed with this technique. Due to poor preservation conditions only eight human from Lapa do Santo and 22 faunal samples from Lagoa Santa provided collagen with an acceptable C:N ratio between 2.9 and 3.6. The material was analyzedin three different laboratories: the Dorothy Garrod Laboratory for Isotopic Analysis of the McDonald Institute for Archaeological Research, University of Cambridge (UC); the Laboratório de Ecologia Isotópica (Isotope Ecology Lab) at the Escola Superior de Agricultura Luis de Queirós, University of São Paulo (ESALQ-USP); and the isotope facilities at the Max-Planck Institute for Evolutionary Anthropology (MPI-EVA).

Results for the fauna are mostly consistent with their dietary habits. Deer (Mazama sp.;Cervidae, Goldfuss 1820) are browsing animals, and in the savannas of central Brazil normally feed on more ¹³C-depleted gallery forest plants. Their predominantly C₃ plant based diet is compatible with the observed collagen isotope values of d¹³C -20.7±1.6‰ and d¹⁵N 6.0±1.9 ‰ (1 sigma interval, n=10). Tayassuidae (Palmer 1897) have generalist omnivore diets. The total of 6 analyzed collagen samples of this animal clustered into two groups of three samples each. One group has a typical C₃ type herbivore diet, very similar to that found in deer, averaging d¹³C -22.5±1.0‰ and d¹⁵N 4.7±0.5‰; whilst the other group has a more carnivore-like diet, averaging d¹³C -16.5±1.0‰ and d¹⁵N 9.7±0.3‰. This difference could be due to a number of reasons such as their broad alimentary range, inter-species variation, environmental changes, or the small sample size. Both armadillo species, Dasypus novencinctusand Euphractus sexcinctus (Dasypodidae, Gray 1821) are omnivores with a tendency to carnivory. Both species have collagen isotope values compatible with a carnivorous behavior averaging d¹³C -14.9±1.7‰, d¹⁵N 8.2±0.5‰ (n=3) and d¹³C -18.4‰, d¹⁵N 8.2‰ (n=2), respectively.

The human results are invariant in their d¹³C values, displaying a mean of d¹³C -19.0±0.6‰ and, therefore, indicating a predominately C₃ based diet. The d¹⁵N values range from 5.3 to 11.3‰. The most enriched d¹⁵N value comes from an infant with non-erupted permanent dentition and probably reflects breastfeeding. Sub-adults with erupted permanent deciduous already have d¹⁵N values more similar to adults. The low d¹⁵N values in the adult population is distinct from the carnivores (t=4.50; p=0.001) and similar to the herbivores from Lagoa Santa region (t=0.25; p=0.400), suggesting a diet based on plants and supplemented by fauna. This is consistent with zooarchaeological studies from central Brazil pointing to a generalist diet mostly based on the gathering of plants but supplemented by small game.