Ornaments such as beads are among the earliest signs of symbolic behavior among human ancestors. Their appearance signals important developments in both cognition and social relations. This paper describes and presents contextual information for 33 shell beads from Bizmoune Cave (southwest Morocco). Many of the beads come as deposits dating to ≥142 thousand years, making them the oldest shell beads yet recovered. They extend the dates for the first appearance of this behavior into the late Middle Pleistocene. The ages and ubiquity of beads in Middle Stone Age (MSA) sites in North Africa provide further evidence of the potential importance of these artifacts as signals of identity. The early and continued use of Tritia gibbosula and other material culture traits also suggest a remarkable degree of cultural continuity among early MSA Homo sapiens groups across North Africa.

In estuarine environments there are important spatial and temporal changes in both salt and suspended load concentrations. An experimental procedure have been developed to produce kinetic parameters being representative of the natural environment studied, and we have investigated the effect of salinity and suspended load concentration to the kinetics of the uptake. These results are encouraged by recent advances in environmental modelling concerning to radionuclide dispersion in aquatic natural systems and involving non-equilibrium processes. Experiments are carried out with unfiltered water samples from the Odiel estuary (Southwest of Spain), with 133Ba tracer to illustrate experimental procedures.

Global fallout is the main source of anthropogenic radionuclides in the Mediterranean Sea. This work presents 137 Cs, 239+240 Pu and 241 Am concentrations in the water column in the southwest Alboran Sea, which was sampled in December 1999. A sediment core was taken at 800 m depth in the area (35°47 0 N, 04°48 0 W). 210 Pb, 226 Ra, 137 Cs and 239+240 Pu specific activities were measured at multiple depths in the core for dating purposes. 137 Cs and 239+240 Pu profiles did not show defined peaks that could be used as time markers, and they extended up to depths for which the 210 Pbbased constant rate of supply (CRS) dating model provided inconsistent dates. These profiles can be useful to test dating models, understood as particular solutions of a general advection-diffusion problem, if the time series of radionuclide inputs into the sediment is provided. Thus, historical records of depth-averaged 137 Cs and 239+240 Pu concentrations in water, and their corresponding fluxes into the sediment, were reconstructed. A simple water-column model was used for this purpose, involving atmospheric fallout, measured distribution coefficient (k d ) values, and a firstestimate of sedimentation rates. A dating model of constant mixing with constant sedimentation rate was applied successfully to three independent records (unsupported 210 Pb, 137 Cs and 239+240 Pu), and provided the objective determination of mixing parameters and mass sedimentation rate. These results provide some insight into the fate of atmospheric inputs to this marine environment and, particularly, into the contribution from the Chernobyl accident.

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