[Archport] ...no seguimento do email anterior sobre "Preservação de Material Osteológico"

["Francisca Alves-Cardoso" <francealves@netc.pt>]

---------- Forwarded message ----------
From: MILLARD A.R. <a.r.millard@durham.ac.uk>
Date: 2008/6/12
Subject: Re: [BABAO-L] The Washing of Bones
To: BABAO-L@jiscmail.ac.uk


Alan

Whilst I agree with the quotes from Martin Jones' book, it is important to remember the timescale to which they apply. Over the long term the interaction of bone with water is one major factor in any degradation process: it is through water that material is lost or gained from bone, and water is the agent for hydrolysis of proteins and DNA. Water and high temperature are together more destructive than either alone, but even when Matthew Collins and Angela Gernaey did simulated degradation experiments, they were running for several months at high (up to 100 oC) temperatures to simulate long periods in the ground. Likewise for dissolution of bone at neutral pH, Robert Hedges and I estimated that it would take 50,000 changes of water to half-dissolve bone mineral. We didn't consider the precipitation of minerals from hard water but it would probably require repeated cycles of washing and air-drying to add a measurable amount of material. I don't know of any demonstration that washing has added mineral.

So one wash and dry at ambient temperatures is unlikely to be important in the *degradation* of bone mineral or biomolecules. As Bill noted, I have raised the possibility of the increased solubility (and therefore loss) of lipids being an issue if hot water is used.

However, introduction of contaminating material into bone is a risk of washing. The water can introduce DNA from those doing the washing, which is Matthew Collin's worry, and of course it leaves the bone surfaces available for handling and contmination as well. Soil particles can also be carried further into a bone by agitation during washing. It might be advisable to retain some portion of a skeleton unwashed for the possibility of future ancient DNA analysis, just as I recommended (Millard 2001) that if consolidation is required some portion is left unconsolidated for future biomolecular analysis.

Relevant literature:

Hedges REM & Millard AR (1995) Bones and groundwater: towards the modelling of diagenetic processes. Journal of Archaeological Science 22: 155-164

Millard AR (1998) Bone in the burial environment. In Corfield M, Hinton P, Nixon T & Pollard M (eds) Preserving Archaeological remains in situ, Museum of London Archaeology Service, London. pp. 93-102.

Millard AR (2001) Deterioration of bone. In Brothwell D & Pollard M (eds) Handbook of Archaeological Sciences. Wiley. pp.633-643.

Collins M,  Gernaey A,  Nielsen-Marsh C,  Vermeer C, Westbroek P (2000) Slow rates of degradation of osteocalcin: Green light for fossil bone protein?. Geology 28(12): 1139-1142

Best wishes

Andrew

--
 Dr. Andrew Millard                       A.R.Millard@durham.ac.uk
 Durham University
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