Renewed in-depth multi-disciplinary investigation of a large coastal mound settlement in Peru has extended the occupation back more than 7000 years to a first human exploitation ~13720 BP. Research by the authors has chronicled the prehistoric sequence from the activities of the first maritime foragers to the construction of the black mound and the introduction of horticulture and monumentality. The community of Huaca Prieta emerges as innovative, complex and ritualised, as yet with no antecedents.

Archaeological excavations in deep pre-mound levels at Huaca Prieta in northern Peru have yielded new evidence of late Pleistocene cultural deposits that shed insights into the early human occupation of the Pacific coast of South America. Radiocarbon dates place this occupation between ~ 14,200 and 13,300 cal yr BP. The cultural evidence shares certain basic technological and subsistence traits, including maritime resources and simple flake tools, with previously discovered late Pleistocene sites along the Pacific coast of Peru and Chile. The results help to expand our knowledge of early maritime societies and human adaption to changing coastal environments.

Chewing coca in South America began by at least 8000 cal BP: our authors found and identified coca leaves of that date in house floors in the Nanchoc Valley, Peru. There were also pieces of calcite — which is used by chewers to bring out the alkaloids from the leaves. Excavation and chemical analysis at a group of neighbouring sites suggests that specialists were beginning to extract and supply lime or calcite, and by association coca, as a community activity at about the same time as systematic farming was taking off in the region.

Debris flows caused by El Niño events, earthquakes, and glacial releases have affected northern Perú for centuries. The Muralla Pircada, a northeast-trending, 2.5 km long stone wall east of the Santa Rita B archaeological site (Moche-Chimú) in the Chao Valley, is field evidence that ancient Andeans recognized and, more importantly, attempted to mitigate the effects of debris flows. The Muralla is upstream from the site and is perpendicular to local drainages. It is 1-2 m high, up to 5 m wide, and is comprised of intentionally-placed, well-sorted, well-rounded, 20-30 cm cobbles and boulders from nearby streams. Long axes of the stones are gently inclined and parallel local drainage. Case-and-fill construction was used with smaller cobbles and pebbles used as fill. Pre-Muralla debris flows are indicated by meter-sized, angular boulders that were incorporated in-place into construction of the dam and are now exposed in breeches in the dam. Post-Muralla debris flows in the Chao Valley are indicated by meter-sized, angular boulders that now abut the retention dam.

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