Sheep Mummy Shows Limits on DNA Longevity
Under ideal conditions, DNA from a sheep in a salt mine
lasted 1,600 years. But could it last millions of years?
DNA that is “extremely well preserved” has been analyzed from a sheep mummy found in an Iranian salt mine. Salt, as everyone knows, is a good preservative of meat and animal tissue. Scientists consider the conditions in the mine ideal for preservation. Even so, it was not perfect, and some degradation was observed after 1,600 years since the sheep died. How long could the DNA have lasted? This bears on the important question of soft tissue preservation in dinosaurs and other fossilized remains.
The research was published originally as a preprint on bioRxiv:
Rossi et al., “Exceptional ancient DNA preservation and fibre remains of a Sasanian saltmine sheep mummy in Chehrābād, Iran,” bioRxiv 22 April 2021,
A newer peer-reviewed version has been published in Biology Letters. A link will be provided when it is found.
The UK Daily Mail printed a detailed report on July 13 with photos:
Ewe have got to be kidding me! 1,600-year-old mummified SHEEP is discovered in an Iranian salt mine with perfectly preserved soft tissues (UK Daily Mail). Salt removes water from a corpse, preventing most bacteria from invading and degrading the soft tissues. Ewe! indeed. This specimen was so well preserved, though, that the DNA was able to be sequenced by researchers.
…This natural process, where water is removed from a corpse, preserving soft tissues that would otherwise be degraded, has been seen in human remains from the mine.
There were longer length fragments of DNA and less damage than would be associated with the remains of something 1,600 years old.
Pristine DNA recovered from 1,600-year-old sheep mummy (Live Science). The sheep leg was “likely discarded by hungry mine workers” writes Nicolette Lanese. That careless act led to an investigation into soft tissue preservation.
The DNA molecules were “so well preserved and not fragmented, despite their age,” senior study author Kevin Daly, a research fellow at the Smurfit Institute of Genetics at Trinity College Dublin, told Live Science. This immaculate preservation not only allowed the team to examine DNA from the sheep, but also the genetic material of salt-loving microbes that grew on the specimen, the team reported in a new study, published July 13 in the journal Biology Letters.
The statement implies that it is normal for microbes to grow on dead animals and quickly degrade the tissues and DNA. But even with high salt concentrations, there will still be some salt-loving microbes able to participate in the decay process. After death, the body’s own enzymes participate in degrading the carcass. In the preprint, the authors say, “The highly alkaline, cool and anhydrous conditions may have contributed to inhibition of cellular nucleases which would otherwise degrade and fragment endogenous DNA.”
Ideal conditions slow down the decay process, in other words, but do not stop it. Live Science says,
Zooming in on the sheep DNA, the team found that the genetic material showed remarkably low levels of fragmentation compared with Iranian sheep bone samples of a similar age. The sample also showed extremely low levels of deamination, a process by which enzymes remove so-called amino groups from molecules that make up the rungs of the DNA double helix. Ancient DNA samples often come heavily scarred by deamination, but not in this case.
Eight mummified humans, called “the salt men,” have been found in these salt mines over the years. The article says some of them are 2,500 years old, complete with preserved hair and skin.
The papers and articles do not address an important implication: given this state of preservation, with some decay, in 1,600 years, what is the maximum lifetime of DNA in fossils buried in the ground in less-than-ideal conditions? It would seem that unrelenting processes of decay would render any DNA unrecognizable within a few thousand years – certainly not millions.
This discovery of relatively-intact DNA in a sheep mummy only 1,600 years old kept preserved in a salt mine provides an important data point in the controversy about soft tissue preservation. Evolutionists glibly assume that DNA in ancient fossils like dinosaurs can persist for 65 million years or more, because the dinosaurs are ‘obviously’ that old. But DNA cannot endure the ravages of time indefinitely. Empirical evidence shows it can last a few thousand years under ideal conditions. The conditions for most fossils are far from ideal! We know that animals that die on the ground are made quick work of by fungi, worms, insects and bacteria. Animals that get buried in mud or sediment (in order to fossilize in the first place) are subject to decay enzymes, burrowing animals and microbes. The surprise in this story is that the sheep DNA lasted as long as it did.
If evolutionists are wrong about the age of dinosaur DNA, they are also wrong about the geologic column. And if they are wrong about the geologic column, the whole Darwin house of cards tumbles to the ground. Not that it hasn’t already, but they can’t keep re-assembling it before another breeze of data collapses it again.