Vizcaı́no site, Uruguay

Archaeological evidences are still missing: a comment on Fariña et al. Arroyo del Vizcaíno site, Uruguay. Fariñ a et al. [1] suggest the possibility of human presence ca 30 ka in the Arroyo del Vizcaíno site (AVS) (southern Uruguay). This is based mainly on the record of cutmarks made by human artefacts on Pleistocene animal bones. They also inform of the finding of a single tiny stone tool and few other possible lithic artefacts. Nevertheless, their research has serious methodological problems and important interpretative errors. The context is a hydraulic bone concentration on muddy sediments, which is a physical association in the sense that its behavioural significance is not evident [2]. In a site like AVS, secondary, averaged deposits, are to be expected. Fluvial processes such as traction, friction, mixing, deposition and redeposition of different particles, including bones and lithics, should be considered. It happens that 'Time intervals represented by fossils are not necessarily the same as those represented by sedimentary events in fluvial systems' [3, p. 211], and particles continue accumulating for long periods. This is why this kind of bone assemblage is normally averaged. It is true that '. .. many, if not most, multi-individual concentrations of disarticulated vertebrate skeletal elements preserved in ancient fluvial channels were derived from a preexisting concentrated source' [2, p. 25], but this does not equal single events. Despite the efforts by Fariñ a et al. to reduce AVS to a single event, it is difficult to escape the conclusion that it is an averaged sample. The selection of four Lestodon ribs for dating is not helpful in assuring that they produce independent dates. Under those conditions, it is not safe to pool the results. Fariñ a et al. accept that more than one taphonomic history is written in those bones, which is an honest way to admit its averaged nature. Indeed, they point out the little evidence for major hydraulic transport deduced from the fossil assemblage , but in the electronic supplementary material, they specify 'The presence of coarse grains must have been due to high-energy events. .. Those pebbles must have transported as bed load together with the transported bones, perhaps in more than one event'. It is very difficult to make compatible 'little evidence of major fluvial transport' with several events of 'high energy'. The authors include a significant taxonomic list, but from the way the taxonomic data are presented, …