Recovery of proteins
Almost certainly more is known about the persistence of proteins than any other biomolecule in the archaeological record, as a result of both the recovery of collagen for 14C dating and δ13C, δ 5N analysis and by virtue of the measures of decay for dating (recently rejuvenated in the UK by North East Amino Acid Racemization (NEaar)), using the so-called ‘Intra-crystalline protein degradation’ approach’ (IcPD).
Free amino acids (FAA) vs Total hydrolysable amino acids (THAA) plot for Asx D/L measured in Scottish archaeological Patella; error bars represent one standard deviation around the mean for each site. Modern (collected in 2001 AD) Patella D/L values are also plotted for comparison (from Demarchi et al. 2010)
As a consequence of these methods it is known that proteins will display measurable levels of deterioration in post-Roman samples even if protected from microbial decay. However it is also known that proteins in protected environments, such as bone collagen, have the potential to persist in all archaeological samples recovered from Scotland.
New directions
(See also Section 1: Chronology)
Stable isotope analysis
Improvements in amino acid analysis, specifically single compound amino acids δ13C and δ 5N hold promise of a more subtle interrogation of bone proteins. As an example it would be possible to obtain greater understanding of the reliance of humans on coastal resources and of the key dietary transitions in Scottish pre- and proto-history.
Proteins in ceramics
Interface samples (such as pottery crusts) represent an intermediate type of survival, and we do not know what information will be preserved in them. However there is encouraging research from Solazzo et al. (2008) and Stevens et al. (2010) suggest that it may be possible to identify proteins in some ceramics. This would be potentially useful in order to investigate dietary change, because specific animal and plant proteins (e.g. gadoid myoglobin, albumin, sheep casein) may be identifiable from sherds.
ZooMS (Zooarchaeology by Mass Spectrometry)
Protein is present as collagen in almost all Scottish archaeological bone (as well as dentine, ivory and antler). The development of a new high-throughput screening technique using soft-ionisation mass spectrometry to fingerprint collagen peptides has potential for protecting morphologically valuable remains from destructive analysis. ZooMS can discriminate small particles of bone to genus level, offering a new approach to rapidly characterise unidentifiable bone fragments (such as cetaceans) routinely and at low cost. One potential application would be to identify additional human material in Mesolithic shell middens, which have been the focus of intense interest in order to understand the dating of the arrival of Neolithic populations, the use of middens as burial sites, and the different approaches to marine exploitation.
ZooMS also appears to be able to recover sufficient collagen from some cremated remains for identification. A new direction is the detection of proteins in eggshells. The recent colonisation of fulmar in the 20th century has been attributed to the increased access to by-catch. However claims for the detection of fulmar in Viking levels at Freswick Links, suggest a more complex pattern of dispersal.
ZooMS discrimination of animals from bone collagen peptides. Data replotted from Buckley et al. 2009