Exceptional ancient DNA preservation and fibre remains of a Sasanian saltmine sheep mummy in Chehrābād, Iran
Résumé
Mummified remains have long attracted interest as a potential source of ancient DNA.
However, mummification is a rare process that requires an anhydrous environment to
rapidly dehydrate and preserve tissue before complete decomposition occurs. We
present the whole genome sequences of a ~1600 year old naturally mummified sheep
recovered from Chehrābād, a salt mine in northwestern Iran. Comparative analyses of
published ancient sequences revealed remarkable DNA integrity of this mummy.
Hallmarks of postmortem damage, fragmentation and hydrolytic deamination, are
substantially reduced, likely due to the high-salinity of this taphonomic environment.
Metagenomic analyses reflect the profound influence of high salt content on
decomposition; its microbial profile is predominated by halophilic archaea and
bacteria, possibly contributing to the preservation of this sample. Applying population
genomic analyses we find consistent clustering of this sheep with Southwest Asian
modern breeds, suggesting ancestry continuity. Genotyping of a locus influencing the
woolly phenotype showed the existence of an ancestral ―hairy‖ allele in this sheep,
consistent with hair fibre imaging, further elucidating Sasanian-period animal
husbandry.