ETA: would like the scholars of salon to take a look at this paper and see if you buy their historical argument that these were probably Louis XVII and Marie-Therese's hair locks. It sounded plausible to me, but, well, a lot of things sound plausible to me :P I assume the DNA analysis part is correct!

I have to work, so no elaboration now, but I've read the paper and done some googling, and both the history and the DNA analysis seem suspect to me. That doesn't mean the conclusion is wrong, but there are so many red flags that the most generous conclusion I can draw is that the write-up is sloppy, and that doesn't inspire confidence that the work wasn't equally sloppy.

I also got my hands on the paper that analyzed the purported heart of Louis XVII, and *wow* was it more professional.

More when I have time!

I find ijsciences on a couple of lists of "predatory journals."

Ahh, good thinking! This surprises me not at all, given the paper.

"The price is low, but the cost of having your research appear here will be high" for another journal is hilarious.

Okay, on to the red flags!

Red flag 1. If you're attempting to sequence DNA, your number one concern should be contamination. Everything that has come into contact with the sample could deposit DNA on it, which will show up in your sequencing. When your sample is 200 years old, that's time for a lot of contamination!

Contamination isn't mentioned by Lucotte (the author of the Louis XVII's paper) at all. What precautions they took around not introducing new contamination, and how they dealt with the possibility of existing contamination, was one of the things I was looking for, and when I didn't see it, alarm bells started going off.

In contrast, Jehaes et al. 2001 (the Louis XVII's heart paper) has an entire paragraph dedicated to this subject, opening with:

From the outset of this study, every effort was made to recover ancient DNA samples free of contamination by contemporary DNA.

Related to this is the total lack of any consideration that the color of the hair samples might be due to environmental considerations over the last 200 years. Even Selena knew to comment when Martin Katte opened Hans Hermann's coffin and found him to be a blond, that this might be because the body had lain in a rotting coffin for hundreds of years.

If you read Lucotte, you'll think everything was handed to him in pristine condition through a time machine by lab scientists who took all the appropriate precautions. Contamination, what's that?

Red flag 2. When you amplify the DNA in a 200-year-old sample using PCR, you're almost certainly going to find DNA sequences from different people who've handled the lock of hair before your team (who hopefully used precautions) came into contact with it.

No mention of this in Lucotte 2019. The analysis he presents is that the Y chromosomes between Louis XVI and Louis XVII totally lined up, with the exception of one question mark where they apparently didn't have a data point. Wow, everything lined up perfectly! He's either not looking for contamination, or he's cherry-picking the results that gave the conclusion he wanted.

In contrast, Jehaes 2001 repeatedly mentions when the authors suspected contamination, and when they had to throw out results because of it:

In one DNA extract of the heart muscle, the same sequence was also observed but with a minor contamination.

The long fragments (whole HV1 and HV2) showed a mixture of two sequences at three positions which could be due to contamination. Therefore the sequencing results of these extracts were not reliable.

The second hair of Marie-Antoinette (Cannes) showed multiple ambiguous positions, which indicated contamination.

So either Lucotte filtered out any non-matching DNA without mentioning it (bad science writing), or he didn't look for contamination (bad science). If the latter, either he got super lucky and he's looking Louis XVII's DNA, or we could be looking at any male here.

Red flag 3: The confidence attached to the statistical analysis (or lack thereof) in the conclusions. So you know how I was suspicious that the two Y chromosomes lined up with basically 100% agreement in the alleles? The authors decide that this means they can declare with 100% confidence that:

The Y-STRs profile obtained is strictly identical to that of Louis XVI (Lucotte et al., 2016). This establishes that Louis XVI is the biological father of Louis XVII.

Or, that this sample was taken from one of his brothers? Or his father? Or any number of other possibilities (one of which I'll discuss below)? "This establishes" on data like this is not responsible science.

In contrast, Jehaes 2001 discusses the strength of their conclusions and admits there are limits to what we can conclude:

This means that it is 166 (or 206) times more likely that the heart is from a member of the Habsburg family than from an unrelated individual.

It is of course impossible, based on these results, to prove that it belonged to the son of Louis XVI and Marie-Antoinette and not to another maternal relative of the Habsburg family. Indeed, only historic data will, in the absence of nuclear markers of the child and his parents, be able to fill this gap.

Red flag 4: My eyebrows flew up at "in some present time descendants of Marie-Antoinette (notably for the present day living Queen Anna of Romania)," because I was pretty sure that MA's daughter didn't leave any known descendants, and that the study of the heart (remember, I own a book on this subject) used descendants of MA's sister(s). Sure enough, Jehaes 2001 says, " living maternal relatives of Louis XVII and his two aunts and mother."

Red/yellow flag 5: The author is comparing DNA that he's decided is from Louis XVII to DNA that he decided in a previous paper belonged to Louis XVI. Now, I haven't read his previous paper, but the moment I see someone repeatedly citing themselves, I have to go see if I can find anything out about the quality of this person's other work. Obviously, people build on their previous work! But if this paper is this sloppy, then the previous paper may have been equally sloppy, and now my uncertainty that the author's found anything is compounded. I call this "house of cards" research.

So I went and looked at what other work he's done.

Well, Wikipedia says Lucotte has been basically ostracized from the scientific community for his opinions on race. I read his quotes and realize that while I disagree with them, they're not necessarily worse than what a lot of reputable scientists say, and he may have been quoted out of context. So we'll let that slide.

But he's also 100% sure that the Argenteuil Tunic was worn by Jesus and that he has Jesus' DNA! And that based on his analysis, Jesus was an opium addict and had crabs!

Oh, look, he does believe in the existence of contamination when it involves other scientists claiming that the tunic only dates from the 6th-7th century CE. No, it's real and it was Jesus's! Oh, and according to this review (I haven't bothered tracking down the actual article), okay, I have to quote this delightful phrasing:

The Vatican will be happy to learn that he shaves once a week, was addicted to drugs and had crabs ...

Congratulations, Lucotte, your scholarship is worse than Goldstone's!

(Just to be clear, the conclusions are Lucotte's, the "Vatican" phrasing is the reviewer getting sarcastic.)

So in conclusion, nothing about the identical alignment of the Y chromosome alleles in his Louis XVII sample and his Louis XVI sample allows me to distinguish between these scenarios:

1. Louis XVI was the father of Louis XVII.
2. The same male assistant working in Lucotte's lab handled both samples.

There are many other scenarios I could go into, but won't bother. This was a totally enjoyable way to spend my lunch break, though. :)

I figured you might well know more about DNA testing than I did :)

So the thing is, I got interested in genetics about 10 years ago, and a couple of times since then I've thought, "Wouldn't it be cool to do bioinformatics for a living?" and started trying to teach myself enough to change careers. I always get sidetracked by things like "Frederick the Great," which shows that I'm not committed enough to give up my hobbies long enough to make it happen. But it does mean that I can read papers like this and know at least some of what I should be looking for.

There's also the part where my main, non-career interest in genetics is paleoanthropological, where contamination is a big, big deal. All the more so because 40,000 years' worth of DNA degradation means there's a whole lot less intact original genomic material to work with. So I just happen to know a thing or two about what you do and do not do when you get your hands on some old DNA. (And I kind of laughed at the paper calling Louis XVII's DNA "ancient." It's all perspective, I guess!)

This is also why when salon starts talking about "Just how inbred was the genetic wonder of Spain, anyway?" I start calculating coefficients. ;)

where they're claiming the whole 100% identical thing, which I missed the first time around, and yeeeeeah that's a red flag.

You know, even on the Jerry Springer-type talk shows that my mother and sister used to watch in my vicinity, where they try to establish paternity in the most dramatic way possible, I remember overhearing things like, "Based on these DNA results, there is a 99.xx percent probability that you are/are not the father," not "This establishes that you truly are the father."

So when I read about 100% certainty based on 100% alignment, I start thinking, "Maybe we've proved that grad student A is the same person as grad student B who needs a better advisor." :P