Biocodicology - A Deeper Dive

[Bernd]

Thanks, this is indeed fascinating!

from a DNA end deanimation point of view (a chemical sign of ancient DNA degradation), parchment appears to be a better conservation environment than inside bones as less of this type of damage was seen as compared to what would be expected for DNA of the same age isolated from bone.

I would not have expected this if we consider DNA is usually sampled from deep within bones which had been in the ground at a low temperature. Still depends a lot on soil chemistry. Anything from an acidic bog usually has very poor DNA preservation - if bones are preserved at all - compared to a dry cold limestone cave.

But it may well be that the tanning process of parchment is a double edged sword. Surely a lot of DNA is destroyed in the process, but a portion is likely stabilized by tannic acid which is known to tightly bind to DNA. Still unexpectedly good results considering only the very surface of the parchment was sampled where we would expect maximal damage due to exposure to the environment and DNAses from microorganisms.

Regarding population isolates, I think this is a matter of trade routes. In regions without frequent long distance livestock trade such as an alpine valley, one would expect more isolated populations than in a busy trade hub like a big town along an important road which frequently imports animals.

My question - assuming DNA fragments from multiple humans are isolated, what are the current limits of sorting and using them for SNP analysis? Has this been tested? Next Gen Sequencing already is extremely challenging for microorganisms in environmental samples but at least these are highly dissimilar compared to humans.