Student Questions: Exploding Teeth and Reproductive Rocks

by Brian Dunning
December 10, 2024

The student questions episodes are among my very favorites to record. On the one hand you could argue that everyone has access to the Internet, everyone can look up any question and have it answered instantaneously; but on the other hand, you could look at where today's young people are getting their information and it's often coming mostly from TikTok. In real life, young people ask me questions about weird things they heard, often conspiracy theories or some crazy pseudoscience scheme, and they often genuinely do not know because they've been exposed to contradictory sources. Thus, the reason these are my favorite is because they are honest questions from people who genuinely do not know.

So let's get started:

Exploding Teeth

Hi Brian, my name is Luna. I've heard before modern dentistry, people's teeth used to explode. I am very skeptical of that. Is it true? Thanks.

Well, I am skeptical of it too. And it's not really something you can look up on the Internet and expect to learn the facts. The BBC published an article about this on their website back in 2016, and it seems to be the genesis of any other stories you'll read today. This article was based on the original source, an 1861 two-page article in the journal Dental Cosmos, titled "Explosion of Teeth with Audible Report."

Most accounts of this say that it happened before about 1920, when dental amalgam used to make tooth fillings was standardized; so some stories say that weird materials used in old fillings may have caused chemical reactions. There are also historical accounts of this happening to people who hadn't had any fillings, and some modern writers have suggested that infections could build up pressure inside the tooth, and decay could even produce gases, either of which could cause the tooth to break open. But "explosion" would be much too dramatic of a word to use for things like this.

Considering the limited number of accounts, and that they were all verbal stories of events without reliable witnesses, probably the majority of the exploding tooth phenomenon comes from writers' embellishments. There certainly are plausible causes for teeth breaking from internal pressures, and that's probably the seed that inspired the 1861 article.

Red Food Coloring and ADHD

This next one is not from a student, but it's about students so that's OK too:

Hi, Brian, this is Jim Vest from Maysville, Kentucky. I'm calling in today because recently my wife and I received a letter from our school son's daycare that was requesting that we limit the amount of red dye that was in the food products we give them as snacks. Now, that made me look into this a little bit, and I was able to find that there is apparently some evidence that shows a link between ADHD symptoms and red dye. I wanted to know what your take on this was.

The idea that red food coloring — specifically, Allura Red AC or FD&C Red 40 — causes behavioral problems in children remains a very tenuous and speculative one. In Europe the red dye is banned in a number of countries; but this isn't because there's any proof, it's because European regulations often tend more toward precaution. Thus they ban certain products like pesticides and biotech that are widely used throughout the rest of the world with no observable consequences.

The fear comes from studies that weren't really applicable, like one that exposed mice to huge amounts of the dye for their entire lives, far more than a person would ever get, and concluded that they were more likely to get colitis. As far as the behavior in children goes, it's been studied many times with only inconclusive reports. The FDA held a hearing in 2011 to study all the evidence, and in the end found insufficient reason to either ban its use or require a warning label. So I wouldn't worry about it.

Is Blood in Veins Blue?

Hello, my name is Matthew and my question is whether blood is actually red or blue, depending on exposure to oxygen.

Yes and no. The color of the blood does change significantly as it travels through the body depositing its oxygen. When it leaves the heart and lungs via arteries, it is bright red as its hemoglobin is bound to lots of oxygen. When it gets back to the heart and lungs via veins, it is a much darker red, but it's never actually purple or blue.

That's not to say that it doesn't look blue. When you see veins through the skin, they often appear bluish on many people. That's the vein, not the blood. The reason arteries don't appear blue is that they're usually deeper and not right there under the skin like veins, in addition to the fact that the lighter blood color blends in more with the other tissues.

Brain Fingerprinting

Hi, Brian, my name is Bernard and I've got a student question for you. Lately I've been looking into the phenomenon of brain fingerprinting and how it has already been used in American and Indian courts. Apparently the science behind it has been not very well peer reviewed. Could you please look into it and tell me what you think? Thank you.

This is actually really interesting. "Brain fingerprinting" is a fancy name for a neurological response to certain stimuli. The effect has been known since 1965. What happens is that when you are shown something, your EEG can actually show certain types of neurological responses. There is a specific brainwave pattern named P300 that appears when you see something that's especially relevant in the current context. So what they're trying to do in the courts is present evidence that the suspect — and I'm just making up an example — had the P300 response when he was shown a picture of the murder weapon, and did not have the response to pictures of unrelated weapons. So it's an attempt to scientifically prove that a person knows something or doesn't know it. Very Star Trek-like.

The problem is that nearly all academic articles on the topic are written by one man, Larry Farwell, who owns Farwell Brain Fingerprinting and sells the service, and nearly all of his citations are of his own work. He claims a 100% success rate, 0% failure rate, and offers a $100,000 prize to anyone who can develop countermeasures to his technique.

The scant few academic papers I could find written by other researchers all came to the opposite conclusion, though: The approach is not a robust and accurate crime-detection tool, and is not supported by enough data to warrant its use in court.

Consciousness After Decapitation

We now have a special guest question, from Dracula himself:

I need to know an answer to a question. When heads are chopped off, do they remain conscious for a few minutes? Thank you very much!

Ah, the eternal question. The consensus is no, there's no way to remain conscious with zero blood pressure in your brain. Once the head's chopped off, the blood squirts right out, and with zero oxygenated blood reaching the brain, you lose consciousness immediately.

We've all heard the old anecdotes about people doing quasi-scientific experiments on people scheduled for execution, mainly in France during the guillotine era — telling the person to blink their eyes for as long as they can, or signal by moving their eyes or mouth. These accounts have to be dismissed as proof of consciousness though. If such movements did occur, they were likely reflexive or spasmodic actions and are not proof of awareness. And what about all the cases where no expected reaction was seen? There could have been 20 times as many; we don't know because those didn't go into the history books.

The Solutrean Hypothesis

Hi Brian, my name is Jeff and my question is about the Solutrean hypothesis. This posits that Stone age peoples from Europe traveled to North America during the last ice age. The hypothesis seems to be based entirely on similarities between flint tools found on the east coast of North America and those found in Spain and western France. Strangely, proponents of this hypothesis never seem to consider an eastern migration that is from North America into Europe. I would appreciate any thoughts you have on this.

Did humans first cross into the Americas from the east or from the west? The consensus has long been from the west, via the dry land bridge from Siberia during the last glacial period. The evidence for the Solutrean hypothesis is, as you note, perceived similarities between American Clovis lithic technology and European Solutrean lithic technology; a perception that very few anthropologists find very persuasive. The evidence against it is at least two very solid lines of evidence.

First is the genetic evidence. We went into this in detail a few episodes ago, in #959 on the Black Olmec conjecture. In short, comparative genomics lets us match up the DNA in ancient gravesites and trace their migration routes back in time, and all indigenous Americans trace back to Siberian populations. None at all has ever come from a European population.

Second is that it was physically impossible for all practical purposes to cross the sea ice of the North Atlantic. The Bering land bridge was dry, with plentiful vegetation and game, and also relatively short. The Atlantic route, however, was thousands of kilometers of thick sea ice, devoid of any food sources or shelter. Some hypothesize they could have gone by boat, but boating technology of the time was limited to dugout canoes incapable of either sustaining passengers for many months or of seaworthiness in North Atlantic seas. The Bering land bridge, however, provided a safe and easy way for thousands of individuals to comfortably take their time migrating.

The Reproducing Rocks of Romania

Hi, my name is Felix. I'd like to know if there's any truth to the rocks in Romania that supposedly move and grow and even reproduce. This does not sound possible to me. Thank you, and Skeptoid is my favorite podcast!

This is sort of true, but also really misleading. The rocks you're talking about are found in only a very few places in the world, and the best known of these is in a park in Romania. They're called Trovanti or trovants, and they're a whole bunch of these weird globular-looking boulders, anywhere from a few centimeters to several meters in size.

Do they actually grow? Yes, they do, but in the same way and at the same speed as cave formations. So you could spend a lifetime watching them and never see any perceptible growth or movement.

They are great balls of calcium carbonate, and when mineral-laden rainwater lands on them, a tiny bit is deposited on the stone, gradually forming layers; and thus they actually do grow, again in the same way as cave formations. It's estimated they may grow a few centimeters every thousand years. Sometimes smaller ones will form on the surface of bigger ones and then break off, and that's how they "reproduce". If that happens, a shift in its center of gravity might cause it to roll a bit, and if they ever do move, that's probably how. It's also been suggested that changes in humidity in the sand they're resting on may cause them to occasionally shift, and while plausible, I couldn't find any record that this had ever been reliably observed.

So they're very cool and really neat to look at, but anything else you might hear is probably exaggerated.

And so we conclude another student questions episode. If you're a student anywhere, and you heard something dubious online or anywhere else, send me a student question. It's easy to do, just come to skeptoid.com/questions and follow the easy instructions. Let's see if Skeptoid can compete with TikTok.

By Brian Dunning
Follow @BrianDunning