The survival of DNA, the most informative biological molecule, for per
iods of at least several thousand years in bone was demonstrated more
than four years ago. However, difficulties with authenticating ancient
DNA have made diagenetic studies problematic. It is therefore essenti
al that these problems be overcome before the question of DNA survival
can be addressed. Here we describe our work with a range of Holocene
skeletal material from domestic animals and humans, and discuss how we
go about authenticating the results. In the first instance, results s
hould be reproducible between different laboratories, in order to elim
inate the possibility of laboratory-specific contamination. The main r
isk is then contamination of the material prior to sampling for DNA. I
t is therefore important to have criteria whereby the authenticity of
the results can be evaluated. These include amplification with species
-specific primers to target DNA from domestic animals, sex determinati
on in humans, and phylogenetic position in both. Since animals can be
tested for the presence of contaminating human DNA, work with animals
can be used to control and assess methodology. Our initial studies in
this area suggest that more than 50% of skeletal remains from the past
two thousand years are likely to contain amplifiable endogenous DNA,
but that in the case of human material great care is needed to disting
uish this from contamination introduced before the samples reach the l
aboratory.