DNA decay rate in papyri and human remains from Egyptian archaeological sites

Abstract

The writing sheets made with strips from the stem (caulis) of papyri (Cyperus papyrus) are one of the most ingenious products of ancient technology. We extracted DNA from samples of modern papyri varying in age from 0-100 years BP and from ancient specimens from Egypt, with an age-span from 1,300-3,200 years BP. The copy number of the plant chloroplast DNA in the sheets was determined using a competitive PCR system designed on the basis of a short (90 bp) tract of the chloroplast's ribulose bisphosphate carboxylase large subunit (rbcL) gene sequence. The results allowed us to establish that the DNA half-life in papyri is about 19-24 years. This means that the last DNA fragments will vanish within no more than 532-672 years from the sheets being manufactured. In a parallel investigation, we checked the archaeological specimens for the presence of residual DNA and determined the extent of racemization of aspartic (Asp) acid in both modern and ancient specimens, as a previous report (Poinar et al. [1996], Science 272:864-866) showed that racemization of aspartic acid and DNA decay are linked. The results confirmed the complete loss of authentic DNA, even in the less ancient (8th century AD) papyri. On the other hand, when the regression for Asp racemization rates in papyri was compared with that for human and animal remains from Egyptian archaeological sites, it proved, quite surprisingly, that the regressions are virtually identical. Our study provides an indirect argument against the reliability of claims about the recovery of authentic DNA from Egyptian mummies and bone remains.

Crosslinks Rather Than Strand Breaks Determine Access to Ancient DNA Sequences From Frozen Sediments

“…It is generally assumed that DNA fragmentation caused by depurination (followed by cleavage of the phosphodiester backbone by b-elimination) is the fastest of the spontaneous chemical reactions limiting the half-life of amplifiable aDNA (e.g., Pääbo and Wilson 1991;Poinar et al 1996Poinar et al , 2002Marota et al 2002). However, the notion behind this assumption remains untested, and some recent studies suggest that crosslinking preventing amplification due to reduced denaturation might be a significant contributor to DNA diagenesis in some environments (Poinar et al 1996;Willerslev et al 2004a;Willerslev and Cooper 2005).…”

Analysis of ancient DNA from coprolites: a perspective with random amplified polymorphic DNA-polymerase chain reaction approach

“…All of these studies focused on the recovery of aDNA from a specific organism or a determined gene sequence. However, recovering aDNA is still a challenge due to aDNA damage and contamination with modern DNA (Hofreiter et al 2001, Marota et al 2002. In this paper we deal with aDNA damage in order to improve the quality and success of methods.…”

“…aDNA retrieved from ancient samples is often degraded into short pieces by hydrolytic or oxidative damage, reducing the possibility of DNA amplification or at least to obtain large polymerase chain reaction (PCR) fragments (Lindalh 1993, Marota et al 2002. Golenberg et al (1996) demonstrated that it is possible to reconstruct degraded DNA by polymerization on self-primed DNA fragments.…”

Ötzi's last meals: DNA analysis of the intestinal content of the Neolithic glacier mummy from the Alps

“…The level of aspartic acid (D͞L-Asp) racemization in grass samples (about 3 mg each) coming from the Iceman's outer clothing was determined as reported (12).…”