Christophe Griggo

Long livestock farming history and human landscape shaping revealed by lake sediment DNA

The reconstruction of human-driven, Earth-shaping dynamics is important for understanding past human/environment interactions and for helping human societies that currently face global changes. However, it is often challenging to distinguish the effects of the climate from human activities on environmental changes. Here we evaluate an approach based on DNA metabarcoding used on lake sediments to provide the first high-resolution reconstruction of plant cover and livestock farming history since the Neolithic Period. By comparing these data with a previous reconstruction of erosive event frequency, we show that the most intense erosion period was caused by deforestation and overgrazing by sheep and cowherds during the Late Iron Age and Roman Period. Tracking plants and domestic mammals using lake sediment DNA (lake sedDNA) is a new, promising method for tracing past human practices, and it provides a new outlook of the effects of anthropogenic factors on landscape-scale changes.

New Data on a Pleistocene Archaeological Sequence in South America: Toca do Sítio do Meio, Piauí, Brazil

Sítio do Meio, discovered in the 1990s, showed a sedimentary sequence clearly composed of two sets of deposits separated by a zone of large rockfall from the massive collapse of the shelters overhang. The bottom set, slightly more than 60 cm thick, was trapped between the bedrock (upon which it rested) and the lower part of the roof fall (reaching more than 1 m in the excavation area), and yielded some charcoal without other archaeological material. New excavations, however, have revealed the presence of artifacts, additional charcoal, and an alignment of sandstone blocks providing clear boundaries for the artifact concentration. The typological and technological composition of the artifacts is classic, with tools made by shaping high-quality quartz pebbles and tools made on shaping chips or on chips obtained by bipolar percussion of quartz blocks. Quartzite was also used, but only in the manufacture of larger tools, of certain types. The toolkit is made of several convergent pieces, denticulates, rostres, scrapers, and end scrapers. Radiocarbon dating results indicate a Pleistocene age, corresponding to the end of the mid-Upper Pleistocene (MIS3). These dates confirm that Sítio do Meio is the seventh Pleistocene stratigraphic sequence known from a 20-km-radius zone, coming from different sedimentary horizons, testifying to a human presence that extends from MIS3 until the middle Holocene, in this region of Piauí. Particularly, we observed that this occupation still has periodic gaps, with phases of occupation occurring in either short or long periods. With the new data, we are able to consider the cultural specificities of each set in the context of climate data to better understand the diversity of occupation within a single territory, for example behavioral variation in the management of space, adaptive responses to environmental pressures, or potentially both at the same time.