Claims of extreme survival of DNA have emphasized the need
for reliable models of DNA degradation through time. By analysing mitochondrial
DNA (mtDNA) from 158 radiocarbon-dated bones of the extinct New Zealand moa, we
confirm empirically a long-hypothesized exponential decay relationship. The
average DNA half-life within this geographically constrained fossil assemblage
was estimated to be 521 years for a 242 bp mtDNA sequence, corresponding to a
per nucleotide fragmentation rate (k) of 5.50 × 10–6 per year. With an
effective burial temperature of 13.1°C, the rate is almost 400 times slower
than predicted from published kinetic data of in vitro DNA depurination at pH
5. Although best described by an exponential model (R2 = 0.39), considerable
sample-to-sample variance in DNA preservation could not be accounted for by
geologic age.
journal reference (abstract free): rspb.Biological Sciences>>