Carbon-14 dating of peat-bog bodies
Accurate C-14 dates of samples can only be obtained if the original carbon compounds of the sample material can be isolated and purified prior to dating. In contrast to cellulose and lignin of common plant materials, which are rather resistant to chemical reactions, proteins of animal and human tissues may react chemically with humic matter and other components in bog deposits. Moreover, during the usual purification procedure proteins gradually become hydrolysed and are transformed into water soluble amino acids. Purification and isolation of the original carbon compunds in tissues deposited in bog deposits therefore pose serious problems.
A method of repeated and controlled extraction of such tissues for extraneous carbon compunds, using weak acids and alkalis, has been developed and appears to give consistently pure samples for dating purposes. In the process a considerable part of the tissue is dissolved. In a single case (K-3117) 80 % of the tissue was dissolved, leaving only 20 % for the dating. However, in most cases less extensive degrees of destruction seem satisfactory.
A number of the samples, both body tissues and fragments of animal skin, were treated with preservatives prior to dating. This further complicated the purification and necessitated prolonged extraction procedures. In spite of these difficulties the dating results show little scatter and lie within a rather narrow time interval, viz. the late Bronze Age and PreRoman Iron Age. Only a single sample (K-1396) is slightly younger, but this may be a statistical deviation.
A list of the dated peat-bog bodies is given. The list includes a new date for the Grauballe Man made after a new and thorough purification of the tissue (K-3117). C13 measurements of a number of the samples suggest that the buried people were farmers rather than fishers.
Henrik Taube
