I wonder how many in the scientific community are skeptical and think human contamination is likely? This dirt stuff is pretty nuts.
The researchers doing this work are professionals. Honest skepticism is warranted but as more and more results keep coming in with this method, it will become mainstream science. I see this work as ground breaking research.
Human contamination is always a possibility which is why they look at the length of the DNA they find. DNA fragments over time, so any modern DNA will have long fragment lengths while ancient DNA will have short fragments. If I am understanding the biochemistry correctly, naked DNA is deaminated in the environment over time, so an additional check is to look at the amount of deamination in the recovered DNA. Deamination is the process of removing an NH3 group from cyotisine and replacing it with an O (which is uracil).
They also found bison DNA which isn’t a species currently living in that region.
I found the actual paper to be more clear and better written than the ScienceDaily summary.
Certainly a legitimate concern. The authors maintain:
the results of the population genetics analyses are in accordance with those published by other studies on skeletal genomes from the same region and time period. These observations thus suggest that the DNA has not been significantly affected by modern contamination or leaching through archaeological layers.
Time will tell, but the technique is generating interesting results.
You seem to be intrigued by mtDNA. You will have to add this paper to your files.
@T_aquaticus yes, that they can also have some confidence to identify animal species seems to give weight to the science being valid, as well as being able to identify the mtDNA haplogroup. That is interesting.
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