TY - JOUR

T1 - A modern baseline for the paired isotopic analysis of skin and bone in terrestrial mammals

AU - Doherty, Sean P.

AU - Collins, Matthew J.

AU - Harris, Alison J. T.

AU - Sistiaga, Ainara

AU - Newton, Jason

AU - Alexander, Michelle M.

PY - 2022

Y1 - 2022

N2 - We present the isotopic discrimination between paired skin and bone collagen from animals of known life history, providing a modern baseline for the interpretation of archaeological isotopic data. At present, the interpretation of inter-tissue variation (Delta((skin-bone))) in mummified remains is based on comparisons with other archaeological material, which have attributed divergence to their contrasting turnover rates, with rapidly remodelling skin collagen incorporating alterations in environmental, cultural and physiological conditions in the months prior to death. While plausible, the lack of baseline data from individuals with known life histories has hindered evaluation of the explanations presented. Our analysis of a range of animals raised under a variety of management practices showed a population-wide trend for skin collagen to be depleted in C-13 by -0.7 parts per thousand and enriched in N-15 by +1.0 parts per thousand relative to bone collagen, even in stillborn animals. These results are intriguing and difficult to explain using current knowledge; however, on the basis of the findings reported here, we caution any results which interpret simply on differing turnover rates. We hypothesize that there may be a consistent difference in the routing of dietary protein and lipids between skin and bone, with potentially on-site synthesis of non-essential amino acids using carbon and nitrogen that have been sourced via different biochemical pathways.

AB - We present the isotopic discrimination between paired skin and bone collagen from animals of known life history, providing a modern baseline for the interpretation of archaeological isotopic data. At present, the interpretation of inter-tissue variation (Delta((skin-bone))) in mummified remains is based on comparisons with other archaeological material, which have attributed divergence to their contrasting turnover rates, with rapidly remodelling skin collagen incorporating alterations in environmental, cultural and physiological conditions in the months prior to death. While plausible, the lack of baseline data from individuals with known life histories has hindered evaluation of the explanations presented. Our analysis of a range of animals raised under a variety of management practices showed a population-wide trend for skin collagen to be depleted in C-13 by -0.7 parts per thousand and enriched in N-15 by +1.0 parts per thousand relative to bone collagen, even in stillborn animals. These results are intriguing and difficult to explain using current knowledge; however, on the basis of the findings reported here, we caution any results which interpret simply on differing turnover rates. We hypothesize that there may be a consistent difference in the routing of dietary protein and lipids between skin and bone, with potentially on-site synthesis of non-essential amino acids using carbon and nitrogen that have been sourced via different biochemical pathways.

KW - skin

KW - bone

KW - archaeology

KW - cross-disciplinary sciences

KW - analytical chemistry

KW - stable isotope analysis

KW - COLLAGEN EXTRACTION

KW - STABLE-NITROGEN

KW - TISSUES

KW - DELTA-N-15

KW - DELTA-C-13

KW - CARBON

KW - DIET

KW - STARVATION

KW - HAIR

KW - RECONSTRUCTION

U2 - 10.1098/rsos.211587

DO - 10.1098/rsos.211587

M3 - Journal article

C2 - 35242352

VL - 9

JO - Royal Society Open Science

JF - Royal Society Open Science

SN - 2054-5703

IS - 1

M1 - 211587

ER -