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Comment by pvaldes | Hacker News Reader

If pyroclastic clouds from volcanoes can reach between 250 and 1000 ºC of temperature, and DNA suffers complete degradation at 190 ºC [1], I wonder how they managed to find anything to analyze here.

I wonder also how they discard the possibility of a later contamination.

[1] https://www.researchgate.net/publication/236457118_Thermal_d...

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I'm sure the analysts, the archeologists, and all the others who spent years of their life getting the education to do the analysis and doing the study, never considered this once at all and you're right it was just all solved by a simple internet comment with two minutes of thought and a single link from Google.

This seems to be a common thought pattern on this site and it might actually be interesting to see if there has ever been a case of some person solving hard problems outside of their field with a simple Google search.

Edit: Seems like this accounts only reason for existence is to throw doubt on everything after looking at their previous posts

Given the replication crisis in science, it seems like a lot of scientists are willing to overlook even obvious things as long as they get a paper published.

So, I think these are questions worth asking.

I would imagine that people that got trapped in buildings would have their DNA never reach anywhere near that temperature. In this case it seems like they got the DNA from plaster casts. I could see the very insides of the body not getting above 190.

If the interior of an oven can reach 200–250°C, and water suffers complete evaporation at 100°C, I wonder how pizza does not come out of the oven completely dehydrated.

> I wonder how pizza does not come out of the oven completely dehydrated

Is because water is trapped inside the pizza materials.

DNA and water are very different substances. One is very fragile, the other is practically indestructible

If the temperature changes, water just will change temporarily its state to became ice or vapor, and if that gas is contained, it will return to liquid as soon as the temperature allows it, as many times as needed. When the pizza is out of the oven, the water returns.

DNA can't do this out of a live cell.

DNA chains unzip and split away at 96ºC and then you need a live cell to recreate the molecule again. Lets assume that somebody ordered a pizza in the same year that Pompeii fell, as we know that half of DNA will vanish each 500 years (more or less), today more than 90% of all DNA in the pizza would be lost just by natural degradation. Now put this pizza in the oven at 200ºC and basically most if not all of this survivor DNA will be reduced to ashes.

But they are here talking about not just finding DNA, but also about knowing if was a man or a woman, That's even more impressive. Those tiny fragments of DNA survivor should belong also to identifiable parts of the X and Y chromosomes.

In this terms, finding "Y" means man, but not finding it does not mean woman. It means either woman or a man where all the short Y chromosome was included in the 99,99% of the DNA lost just by chance in the taken sample. This means that some of the identified girls could be really boys.

dna gets destroyed, dnatured all the time. its just sugarcotton with extra ingredients .

Evaporation cools the interiorvfor quite a while and the pyroclastic stream is just one trainload of heat and death for maybe half an hour. So the marrow aint cooked, its fresh and all the bacteria is denatured, the environment is a ashy cement tomb, so all liquid evaporating from the dna shards is take up by the surrounding ash-cement capsule. Not an expert ,just an enthusiastic guesser.

This is my question as well. How do they know that these DNA samples are not of the people who prepared and/or maintained the casts?

There are a couple of ways to rule out modern contamination.

Ancient DNA has certain characteristic damage that changes the sequence slightly, and you can use that to filter out any DNA that doesn't have that signature. Plus, you can maintain DNA profiles of all people involved in handling to ensure it's not modern contamination from the field workers or lab techs.

These makes sense.

Thanks for clarifying.

3 people downvoted me for the honest question.

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