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Commonly applied a priori assumptions of U uptake, such as early uptake or linear uptake, are inadequate because they have no physical or chemical bases, no means of demonstrating which model is suitable for a particular bone, and no intrinsic tests of reliability.Despite this and numerous examples of anomalous U-series dates, such assumptions are still routinely applied.We address this problem using the diffusion-adsorption (D-A) model of U uptake (Millard and Hedges, 1996), which incorporates a physicochemical description of U uptake.Using this model, we show how the U uptake of a bone responds to geochemical changes in the burial environment, which can lead to phenomena such as the removal of U from bones (“leaching”) or U uptake late in their burial history (“recent uptake”), and we show how the overall uptake history is reflected in distributions (profiles) of U and U-series isotopes across a bone section.

Plants take up c14 along with other carbon isotopes during photosynthesis in the proportions that occur in the atmosphere; animals acquire c14 by eating the plants (or other animals).

During the lifetime of an organism, the amount of c14 in the tissues remains at an equilibrium since the loss (through radioactive decay) is balanced by the gain (through uptake via photosynthesis or consumption of organically fixed carbon).

However, when the organism dies, the amount of c14 declines such that the longer the time since death the lower the levels of c14 in organic tissue.

Collagen quality is assessed using %C, %N, C: N, δ13C and δ15N values measured on the sample.

These values are often utilized to determine the diet, paleodiets, trophic levels, and paleoenvironments associated with the bone samples.

Beta Analytic offers two services for bones – standard and priority.

Both services use Accelerator Mass Spectrometry (AMS) technology, which gives the most advanced precision and accuracy.

This means that dates for the final Neanderthals and for the first human occupations of Europe have been unreliable, fomenting the debate.

But over the past decade, Higham and his team have developed techniques that provide more accurate readings in bones up to 55,000 years old (see Nature 485, 27–29; 2012).

The technique is based on measuring the steady loss of radioactive carbon-14 molecules in organic remains.

But after 30,000 years, 98% of the isotope is gone and younger carbon molecules are starting to infiltrate bones, making remains seem younger than they are.