The oxygen isotope composition of human phosphatic tissues (delta18OP) has great potential for reconstructing climate and population migration, but this technique has not been applied to early human evolution. To facilitate this application we analyzed delta18OP values of modern human teeth collected at 12 sites located at latitudes ranging from 4 degrees N to 70 degrees N together with the corresponding oxygen composition of tap waters (delta18OW) from these areas. In addition, the delta18O of some raw and boiled foods were determined and simple mass balance calculations were performed to investigate the impact of solid food consumption on the oxygen isotope composition of the total ingested water (drinking water+solid food water). The results, along with those from three, smaller published data sets, can be considered as random estimates of a unique delta18OW/delta18OP linear relationship: delta18OW=1.54(+/-0.09)xdelta18OP-33.72(+/-1.51)(R2=0.87: p [H0:R2=0]=2x10(-19)). The delta18O of cooked food is higher than that of the drinking water. As a consequence, in a modern diet the delta18O of ingested water is +1.05 to 1.2 per thousand higher than that of drinking water in the area. In meat-dominated and cereal-free diets, which may have been the diets of some of our early ancestors, the shift is a little higher and the application of the regression equation would slightly overestimate delta18OW in these cases.

[1] The timing and causal relationships between the pronounced negative C isotope excursion and paleoenvironmental perturbations associated with the Toarcian oceanic anoxic event (Early Jurassic) remain unclear, particularly because biotic crises and carbonate production decrease appear to have been initiated earlier than the main C isotope anomaly. Here we present a new quantification of Late Pliensbachian-Early Toarcian calcareous nannofossils abundance and size from the Peniche reference section (Portugal) together with O and C isotope records of well-preserved brachiopod shells from the same section. The brachiopod shell d 13C curve parallels that of bulk carbonate and records two pronounced negative isotopic excursions, close to the Pliensbachian-Toarcian boundary ($À2%) and during the Toarcian oceanic anoxic event ($À3.5%). Our results indicate that both C isotope negative excursions were characteristic of benthic and shallow-water environments, suggesting that these two carbon cycle perturbations affected all epioceanic reservoirs. Coeval shifts toward lower values of brachiopod oxygen isotope compositions and closely correlated northward migrations of Mediterranean ammonite fauna suggest that both events coincided with major rises in seawater temperatures, probably as a result of increased CO 2 levels and enhanced greenhouse conditions. CO 2 -induced changes in seawater chemistry likely affected the calcification potential of both neritic and pelagic systems, as evidenced by synchronous drops of platform-derived carbonate accumulation and drastic reductions in size (>3 mm) of the main pelagic carbonate producer Schizosphaerella. We suggest that the Early Toarcian paleoenvironmental crisis occurred in two distinct episodes that were most likely related to two successive phases of intense volcanic degassing in the Karoo-Ferrar province.Citation: Suan, G., E. Mattioli, B. Pittet, S. Mailliot, and C. Lécuyer (2008), Evidence for major environmental perturbation prior to and during the Toarcian (Early Jurassic) oceanic anoxic event from the Lusitanian Basin,