The sambaqui (shellmounds) people are recognized as fisher-gatherers who inhabited the coastal regions of Brazil, with a subsistence on a diet composed of fish, molluscs, and plants. Paleoparasitological investigations in these open-air sites are challenged by the severe taphonomic processes affecting parasite vestige preservation. Previous palaeogenetic work reported parasite helminth infection by Ascaris sp. in an individual from Jabuticabeira II (JABII) sambaqui, located in the Santa Catarina state, Brazil (2890 ± 55 to 1805 ± 65 years BP). To expand our knowledge about helminth infections in sambaqui people, this study applied a palaeogenomics approach in JABII. Sediments from pelvic and sacral regions of 3 JABII individuals and environmental samples underwent ancient DNA extraction and cox1 gene PCRs. High-throughput sequencing data were compared to a custom-built reference database. The JABII dataset revealed reads that are mapped against plathelminth and nematode parasites. Plathelminth observations are probably attributable to pseudo-parasitism and are associated with the animal hosts identified within the JABII faunal assemblages. Two JABII individuals exhibited Anisakis simplex, Contracaecum osculatum, and Ascaris sp. Anisakids are common parasites of marine fish, crustaceans, and mammals that infect humans by consuming fish. Most of the fish identified at the JABII site are currently documented as being infected by Anisakidae. Ascaris sp. is verified in different JABII individuals from the previous study, confirming the spread of this soil-transmitted helminthiasis. The novel data herein agree with the subsistence of the JABII fisher-gatherers, the sedentary lifestyle and the faunal surroundings in the Southern coastal region of Brazil.

Considering the impact of coastal dynamics on the radiocarbon (14C) marine reservoir effect (MRE), upwelling has the potential of enhancing marine influence, usually 14C depleted. Freshwater input can contribute either to increased reservoir offsets, when dead carbon from rock weathering is available, but also towards an atmospheric 14C signal, when the presence of terrestrial organic matter from catchment prevails. An overview of the MRE studies based on shellmounds on the coast of Rio de Janeiro reveals a pattern of negative local corrections for Saquarema and Rio das Ostras but positive values for Cabo Frio island, suggesting the presence of cold upwelling waters in Cabo Frio at 1.6–1.2 cal kBP. New results for a shellmound on the Ilha Grande island, in the western portion of the Rio de Janeiro coast, revealed a negative value at about 3 ka. We discuss distribution of MRE values and temporal variability in the region and their relation to ocean dynamics, continental input and the choice of marine organisms used for ∆R determination. A comparison of local reservoir offsets for the Saquarema region obtained from fish otolith and mollusk shells revealed similar ΔR distributions, showing that both materials can be equally used.

Among other zooarchaeological remains, terrestrial snails’ shells from the Thaumastus and Megalobulimus genera are found in some Brazilian shellmounds, presenting a potential substitute for charcoal in radiocarbon dating analyses, as reliable representatives of the atmospheric carbon isotopic ratio. In this paper, we present statistically similar results of both charcoal and land snails samples from the same archaeological contexts in three settlements on the coast of Rio de Janeiro. The Manitiba I shellmound results range from 4.2 to 3.7 ka cal BP (95.4%), contemporary with the Saquarema shellmound, occupied during the period from 4.3 to 3.6 ka cal BP (95.4%). For the Usiminas shellmound, two groups of samples revealed different periods of time for two occupational layers from 2.3 to 2.1 ka cal BP (95.4%) and from 1.6 and 1.3 ka cal BP (95.4%). A model constraining each group of samples to within a single phase has a general agreement of 97% with only two outliers out of 22 dates, yielding minimum individual agreement of 74% and 7% posterior outlier probability for Saquarema shells. These are good examples of sites in which the occupation chronology can be successfully obtained by the radiocarbon dating of land snails.