Lahar inundated, modified, and preserved 1.88 Ma early hominin (OH24 and OH56) Olduvai DK site.

Archaeological excavations at the DK site in the eastern Olduvai Basin, Tanzania, age-bracketed between ∼1.88 Ma (Bed I Basalt) and ∼1.85 Ma (Tuff IB), record the oldest lahar inundation, modification, and preservation of a hominin "occupation" site yet identified. Our landscape approach reconstructs environments and processes at high resolution to explain the distribution and final preservation of archaeological materials at the DK site, where an early hominin (likely Homo habilis) assemblage of stone tools and bones, found close to hominin specimens OH24 and OH56, developed on an uneven heterogeneous surface that was rapidly inundated by a lahar and buried to a depth of 0.4-1.2 m (originally ∼1.0-2.4 m pre-compaction). The incoming intermediate to high viscosity mudflow selectively modified the original accumulation of "occupation debris," so that it is no longer confined to the original surface. A dispersive debris "halo" was identified within the lahar deposit: debris is densest immediately above the site, but tails off until not present >150 m laterally. Voorhies indices and metrics derived from limb bones are used to define this dispersive halo spatially and might indicate a possible second assemblage to the east that is now eroded away. Based upon our new data and prior descriptions, two possibilities for the OH24 skull are suggested: it was either entrained by the mudflow from the DK surface and floated due to lower density toward its top, or it was deposited upon the solid top surface after its consolidation. Matrix adhering to material found in association with the parietals indicates that OH56 at least was relocated by the mudflow.

Phytolith analysis on dental calculus, enamel surface, and burial soil: information about diet and paleoenvironment.

Silica phytoliths (microscopic remains originating in plant tissues) have been identified on the enamel surface and dental calculus of a sample of teeth selected from well preserved skeletons from a Late Roman necropolis in Tarragona (Spain). Phytoliths were observed by scanning electron microscopy (SEM) and their siliceous nature was confirmed by X-ray microanalysis. The phytoliths were compared to those of soil samples from both the areas of the tombs corresponding to the abdomen and the periphery of the skeletons, and were classified taxonomically by comparison with a large collection of silica particles from modern plants in the Mediterranean area. Most of the phytoliths identified on the enamel and the dental calculus belong to the family of Poaceae, while the phytoliths from the abdominal area belong to Poaceae, Leguminosae, Cyperaceae, and Chenopodiaceae. Results are concordant with archaeological, ecological, and historical data from the same site, and with the human Mediterranean diet. If done properly, the study of phytoliths can provide direct information about the vegetable diet of past human populations, and could be applied to the study of human fossils.