Listener Questions #29

23:43When you need a partner trusted by millions, there's one platform for all business. PayPal Open. Grow today at paypalopen.com. Loan subject to approval in available locations. Eczema is unpredictable, but you can flare less with Epglyss, a once-monthly treatment for moderate to severe eczema. After an initial four-month or longer dosing phase, about 4 in 10 people taking Epglyss achieved itch relief and clear or almost clear skin at 16 weeks. And most of those people maintain skin that's still more clear at one year with monthly dosing. EbGliss, Librikizumab, LBKZ, a 250 milligram per two milliliter injection is a prescription medicine used to treat adults and children 12 years of age and older who weigh at least 88 pounds or 40 kilograms with moderate to severe eczema.

24:25Also called atopic dermatitis that is not well controlled with prescription therapies used on the skin or topicals or who cannot use topical therapies. EbGliss can be used with or without topical corticosteroids. Don't use if you're allergic to EbGliss. Allergic reactions can occur that can be severe. Eye problems can occur. Tell your doctor if you have new or worsening eye problems. You should not receive a live vaccine when treated with EBCLIS. Before starting EBCLIS, tell your doctor if you have a parasitic infection. Ask your doctor about EBCLIS and visit ebglis.lily.com or call 1-800-LILY-RX or 1-800-545-5979.

24:54Aging doesn't stop, and neither should you, with Vital Proteins Collagen and Protein Shakes. Because around the age of 30, your body needs more support for movement and recovery. On workout and rest days, reach for a 30-gram total protein shake or go with our classic collagen peptides. Help support healthy hair, skin, nails, bones, and joints. So you can stay vital, stay you. Visit VitalProteins.com to learn more and where to buy. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

25:35Okay, we're back and we're answering questions from listeners today. questions about beetles questions about space questions about what's going on on kelly's cranium on my cranium how did we get to talking about my cranium are we going to be talking about gray hair salt and pepper silver foxes later oh yeah okay we're back we're back to my gray hairs are we going to talk about my crow's feet too is there anything else you want to point out that's wrong with me daniel i never noticed any crow's feet kelly this is the first i hear about No, no, you're not. You can't walk back the problem you started earlier today, Daniel.

26:11All right, let's let's change the subject and hear what Jane has to say. Hi there, Daniel and Kelly. I've recently heard about the ambipolar field and I'm fascinated to know more. It seems to be independent of the Earth's magnetic field, but I don't understand how that can be. Can you explain? I've also heard that the field is much stronger on Venus and that's one reason why Venus no longer has oxygen or hydrogen in its atmosphere. But why is it stronger on Venus than on Earth? And was it always that strong? If not, might it increase on Earth? I'm loving the show and being able to ask questions.

26:57It's like having a tame professor in the spare room. So I'm really looking forward to hearing your answers to my questions. Thank you. All right. So Jane has a really fun question about electric and magnetic fields around the earth. And this is a field I think a lot of people haven't heard of. Yeah, I don't think that I've heard, or if I have, I've forgotten about the ambipolar field, right? So I'm thinking about ambidextrous and you can switch between left and right. Is that helping me understand ambipolar? No. Okay. So most people are familiar with Earth's gravitational field, right? In a Newtonian picture, gravity is a force and it pulls on stuff and things with more mass get pulled on more strongly.

27:42And that's what holds the atmosphere in place, for example. Or Earth's magnetic field. Magnetic fields are generated by charges in motion. So like currents of magma and other metals inside the Earth, we think, generate the magnetic field, not fully understood with all sorts of weird behavior like the poles move and the poles flip, all this kind of stuff. The ambipolar field is something completely separate from both of those. It's a totally separate effect coming from atoms in the atmosphere being ionized. Oh, all right. So is this going to have anything to do with the aurora borealis? Not directly.

28:19No. but a little bit, you know, a little bit. So what happens is if you have a neutral particle, like you have a proton and an electron, they're bound together. They make hydrogen, for example, everything is happy. But sometimes things get hot and electrons leave their protons. And now you have ions, protons that are positively charged and electrons, electrons are negatively charged and they're separated. So this is like a plasma. And in the upper atmosphere, you have high speeds and not everything is bound together. So there's lots of protons and electrons up there. It's not just all neutral atoms.

28:53So now you have the gravitational force. It's going to pull harder on the protons than it is on the electrons. Why? Because protons are much more massive than the electrons. I remember that. And so what that means is that protons are lower in the atmosphere than electrons. You get this separation because the electrons are lower mass. They're moving faster with the same kinetic energy. So essentially, you get an imbalance, right? Now you have the electrons higher up than the protons. That creates an electric field because you have these charged particles. And when you create a separation of charges, you get a field between them because essentially there's a force that wants to pull them back.

29:31That is an electric field, the ambipolar field in the upper atmosphere of Earth and also Mars and also Venus. So that's what the ambipolar field is. Whoa. Okay. All right. So first of all, can you use that for anything? You can use it to create like a gun of particles out into space. So for example, this field will pull on particles. It'll pull protons up. And in some parts of the Earth, it'll create like a polar fountain. And like at the North Pole, it creates like a font of hydrogen atoms, hydrogen ions actually, shooting up and out of the Earth. I don't know if that's useful for anything, but it's kind of cool.

30:11Okay. Yeah. Neat. And you could also, in principle, use it to help like steer satellites. You know, this one way to steer satellites instead of having thrusters is to like use the Earth's electric and magnetic fields. Like you have a long tether and you twist it and that creates torque or you can use it to create thrust. It's fairly weak though. So not like big satellites or anything, but you know, it adds to the sort of texture of the near earth environment. Okay, awesome. And then, okay, so Earth, Mars, and Venus have it. All right, so what are they? All right, so they all have gravity, but every planet has gravity.

30:46They all have atmospheres, so you need an atmosphere. Although Mars' atmosphere is much, much weaker, so its ambipolar field is also weaker. Yeah, and Mars is like, what, 1 % of Earth's or something? Yeah, exactly. Is that all you need is a gravitational field and an atmosphere to have an ambipolar field? That's almost all you need. You need ions in your atmosphere also. If it's all neutral particles, you're not going to get an ambipolar field. And that's one reason why Venus has a much stronger ambipolar field than Earth. Number one, it has a very dense atmosphere. So there's a lot of electrons and ions to pull apart.

31:20But also, because Venus has no magnetic field, it has no protection from the solar wind. See, we're going to get to the Aurora Borealis connection. And the solar wind is what creates a lot of these ions in the upper atmosphere. So you have energy from space, photons and protons, et cetera. hitting the upper atmosphere, that ionizes it. That energy from space breaks open neutral atoms to create your ion and your electron. And because Venus doesn't have a magnetic field to protect it from the solar wind, a lot of that solar radiation causes more ionization and speeds up those particles because all this energy is coming from space.

31:56And so that gives you a lot of ions and those ions are now moving fast. And so that helps these ions escape. So that creates a very strong ambipolar field on Venus. And this is always sort of counterintuitive, like the electrons get higher, the protons get lower. And so that's the ambipolar field. But then the effect on the other particles is the opposite. That field is always trying to cancel itself out. Electromagnetism is always doing whatever it can to cancel itself out because it's so strong. So you create that field by separating them. Then the field has the effect of pushing the ions up and the electrons down, which is why you get this like font of hydrogen ions in a similar way sort of that if you immerse a metal in an electric field the electrons in that metal will move to counter that electric field because the electric field has pushed on those electrons right so electromagnetism is always doing everything it can to zero itself out it doesn't want to ever do anything it's just so lazy okay so it's stronger on venus so is it stronger on venus for two reasons one venus has a thicker atmosphere, and two, you're more likely to have charged particles in that atmosphere.

33:08Yes, exactly. So it's not directly connected to the magnetic field. It's not caused by the magnetic field in that sense. I think that was Jane's question. But it is indirectly connected because the magnetic field will help you prevent ionization of your upper atmosphere, which would reduce the ambipolar field. And so Venus has a strong one because two reasons. Yes, it has a denser atmosphere, and it doesn't have protection from the solar radiation. Now, we think that a long time ago, Venus was a very different situation. It might have had a magnetic field before its internal bits seized up and it cooled.

33:42It might have had internal motion, which generated a magnetic field, which shielded it from some solar radiation, which would have had less ionization. Now it's lost that magnetic field, so it gets more radiation and a stronger field. Cool. Okay. Now, could Earth get a stronger ambipolar field? Yes. It's possible that our ambipolar field could increase. But for that to happen, we'd essentially have to lose our magnetic field. We'd have to be more susceptible to solar radiation. No thanks. So that could either be we lose our magnetic field, which seems unlikely. I mean, we don't really understand it.

34:17And it's been kind of flip-flopping and sloshing around. but total loss of the magnetic field would require the Earth's internal mechanisms to seize up the way Mars has and Venus has. And that seems unlikely to happen soon because there's still plenty of activity going on inside Earth. If it happened, it would be slow and gradual. Or the other thing is we could have more solar radiation, so we could get more ionization. And that's more unpredictable. Like that just depends on, hey, is the sun going to burp at us some huge blob of plasma that comes and strips away a lot of the atmosphere or ionizes it, that could happen at any moment.

34:53You know, just a few weeks ago, we had really strong aurora boreali. Is that how you pluralize it? You could see them pretty far south in the United States because of the space weather event from the sun. And that comes from not understanding the internal dynamics and the chaos of the sun's plasma well enough to predict that. So yeah, we could get a stronger ambipolar field if we got more solar radiation or if we weakened our protection from it. Either one would give us more ions and therefore a stronger ambipolar field. Neither one of those options sound great for the humans living here. So let's hope it doesn't happen.

35:28All right. Well, let's send that answer to Jane and hear if it freaked her out or made her feel more at one with her understanding of the universe. And let's hear if she's going to kick the professor out of her spare room. Thank you so much for your answer, Daniel. I really feel I understand the ambipolar field now. And I'm very relieved that we're for the most part protected from Venus's fate by our wonderful magnetic field. But I do love the idea of a polar fountain. Sounds like something Santa would have. Oh, and by the way, my spare room is still available for professors if you're ever in the north of England.

36:09Thanks for a great show.

36:20Hey, everyone. It's Cal Penn. I'm the host of Earsay, the audible and iHeart audiobook club. This week on the podcast, I am sitting down with Ray Porter, the narrator of Andy Weir's audiobook project Hail Mary, massive sci-fi adventure about survival and science and what happens when you wake up alone very far from earth. I really had to make a decision because I caught myself getting that frog in my throat and starting to get teary as I'm narrating some of these sections. And it's like, okay, yo, yo, yo, is this indulgent? And I really thought about it. I was like, no, at this point, it would kind of be betraying the trust the author and the listener have in telling this story if I don't go through it.

37:04But there's places in this book that deeply emotionally affected me. and I left it on the mic. That's great. Because it served the story. People will say like, oh my God, I cried at the end. It's like, yeah, dude, me too. Listen to Earsay, the Audible and iHeart audiobook club on the iHeartRadio app or wherever you get your podcasts. Every business has an ambition. PayPal Open is the platform designed to help you grow into yours with access to business loans so you can expand and hundreds of millions of PayPal customers worldwide. Your customers can pay all the ways they want today with PayPal, Venmo, Pay Later, and all major cards so you can focus on the future.

37:44When you need a partner trusted by millions, there's one platform for all business. PayPal Open. Grow today at paypalopen.com. Loan subject to approval in available locations. Eczema is unpredictable, but you can flare less with EpGliss, a once-monthly treatment for moderate to severe eczema. After an initial four-month or longer dosing phase, about four in 10 people taking EpGliss achieved itch relief and glare or almost-clare skin at 16 weeks. And most of those people maintain skin that's still more clear at one year with monthly dosing. EbGliss, LibriKizumab, LBKZ, a 250 milligram per two milliliter injection, is a prescription medicine used to treat adults and children 12 years of age and older who weigh at least 88 pounds or 40 kilograms with moderate to severe eczema.

38:25Also called atopic dermatitis that is not well controlled with prescription therapies used on the skin or topicals or who cannot use topical therapies. EbGliss can be used with or without topical corticosteroids. Don't use if you're allergic to EbGliss. Allergic reactions can occur that can be severe. Eye problems can occur. Tell your doctor if you have new or worsening eye problems. You should not receive a live vaccine when treated with EPCLIS. Before starting EPCLIS, tell your doctor if you have a parasitic infection. Ask your doctor about EPCLIS and visit EPCLIS.lily.com or call 1-800-LILY-RX or 1-800-545-5979.

38:55Aging is real. And so are the benefits of adding Vital Proteins Collagen Peptides to your daily routine. New Vital Proteins Collagen Sparkling Water. Your daily glow-up now in three fresh flavors. strawberry blossom lemon lime and blood orange improved skin health in as little as 30 days thanks to collagen peptides cheers to that or go with our classic collagen peptides so you can stay vital stay you visit vitalproteins.com to learn more and where to buy these statements have not been evaluated by the food and drug administration this product is not intended to diagnose treat or prevent any disease

39:36I don't know, Daniel, if you had a professor in your spare room for questions, would you want a physicist or maybe a less smelly profession? We often have a professor in our spare room because we have a guest room and people come to visit. And sometimes, you know, you invite a friend to come and visit for official reasons to give a talk. But then you also want to hang out with them and you don't want to put them up in a hotel. So they sleep in our spare room and have dinner with us. And that's a lot of fun. So often we have biologists and physicists or physicists usually coming to stay with us.

40:08And our kids have expressed their lack of enthusiasm for physics or biology dominated dinner conversations. Our kids at some point asked us to please stop talking about space law over dinner. Yeah, I understand. All right. Let's move on to our question from Joe. Hi, Daniel and Kelly. I've often heard the claim that stress made me get all these gray hairs. Is there any biological validity to that concept? And if so, what are the mechanisms? Can your emotional state, plus cortisol or dopamine levels perhaps, affect this part of your biology? Finally, has it been observed in any other animals? Thanks so much for bringing some color or salt and pepper to this question.

40:53All right, so Joe's suggesting that gray hair isn't just about age, It might be about stress. It's about like emotional age, not cosmological age. That's right. And so I think it's possible that there are different mechanisms at play here. So let's go ahead and leave my old age-related grays to the side. We don't have to talk about them anymore, actually. Okay. All right. And so to understand what's happening, let's go ahead and talk about the hair cycle. All right. So you have loads of hair follicles on your head. I do. You do. You do. One does. Not only is your hair not gray, but you actually have it covering your whole head.

41:34You are very lucky for a 50-year-old. Or are we rounding up to 100 now? Yeah, exactly. I'm more than 50, so it rounds up. Okay. All right. So each of our hair follicles goes through a cycle, and our hair follicles aren't synced. So our hair follicles tend to be at different stages of this cycle. So, antigen is the part of the cycle where your hair is growing. And for the hair on top of your head, the stage usually lasts about four to six years. Oh, that's all? Yeah. Yeah. Kind of surprising, right? And your hair is growing something like half an inch a year. And early in antigen, what happens is that you have hair follicle stem cells.

42:13And so stem cells are cells that are, they're like, they're like baby stem cells. There's things that they can become, but they haven't become them yet. And these are cells that are going to become hair follicles, but they haven't become them yet. So they're hanging out there. And when the time comes, they will become hair follicles. And they're just waiting for the message. When you get to this early growth phase, these hair follicle stem cells jump into action. They make a hair follicle. And now you've got your hair follicle. All right. So I have stem cells on my scalp my whole life waiting to become follicles.

42:47Cool. Didn't know that. And you also have melanocyte stem cells. And so what they're doing is they're waiting to produce melanocytes. And these are the cells that make melanin, which is the pigment that gives hair color. And so early in antigen, your hair follicle is being made and your melanocyte stem cells are activated to make melanocytes. and the melanocytes will travel down to your hair follicle and they get ready to start making melanin. So now your hair follicle is making the hair, your melanocytes are making the melanin, and now you have hair that has color. And all of my melaninites have to all be coordinated, right?

43:32Because I have like one color of hair on my head and you have a different color of hair and my daughter is blonde, for example. And so there's a genetic coding in there that controls all of the melaninites or melanocytes? Melanocytes. Yes, they're all making the same color. I see. Yeah. Okay, so the thing that's confusing to me is if they only last for four to six years, how come I didn't lose all my hair when I was seven? Because there's a cycle. Okay, so you've got four to six years, and then you go into a phase called the catagen phase, where everything sort of degenerates. You lose the blood vessels, and so now the hair follicle isn't getting oxygen or nutrients, and this lasts about two weeks.

44:11And at this stage, the melanocytes die. But your melanocyte stem cells are still alive. So you still have cells that can make more melanocytes, but the melanocytes that were made a few years ago, they're toast. Okay, and then you go into a resting phase and this can last for a few months where the hair follicle is just kind of chilling out. And then you go into a phase called exogen where the original hair is shed out because you've started the cycle again a new hair is growing and it pushes out the old one, you shed. So you shed something like 50 to 100 hairs a day. And so that's how many hairs are sort of beginning the process anew.

44:50And when you start that process anew, those two types of stem cells wake up again. They start doing their jobs again. And after the new hair follicle has started and after the new melanocytes have gone to work, those two sets of stem cells go to sleep again for like, you know, four to six years or whatever. They do their job. They make the cells that are going to work through the cycle. And then the stem cells go to sleep. Does that make sense? That makes a lot of sense. And it really helps me understand something I remember wondering about when I was like a teenager. Young physicist Daniel was thinking about hair growth the way you think about like radioactive decay.

45:23You know, I was thinking maybe it was like probabilistic and hairs would just like fall out randomly. But if that were the case, you'd start with like a full head of hair and then you just gradually lose hairs until eventually you had like one super long hair. which would be the only thing you had. Clearly that model does not explain the data. So I like your model a lot better. Oh, good. Okay. Well, and there's a lot of variability. Some people have, you know, shorter cycles so their hair doesn't grow as long. And the cycle on your body is much shorter so your body hairs never get as long as the hairs on your head.

45:54But this is like sort of generally our understanding of how the cycle goes on average. All right. And so there's really two different bits there. There's like the hair growing and the hair coloring. And so tell us about why the hair coloring can go wrong or why things turn gray. All right. So I found this amazing paper. Zhang et al. 2020 in Nature did this amazing set of experiments that sort of like deal with tons of different hypotheses. And they really nail it down in mice. So, again, this is in mice. Keep in mind it's in mice, not in humans. But OK, so first they say, if you stress out black mice, will they get gray hairs?

46:30So they stress mice out a couple different ways, and the mice do start going gray. Are they terrible? No, I mean, they're not. They're not the worst I've read about. I have to imagine, how would I stress out a mouse? I might put it in a cage next to a cat. Not to kill it, but just to put it in the cage next to it. That would be pretty stressful for a mouse. Oh, okay. So this is nowhere near that bad, actually. So they would rapidly change the light and dark cycles. They would leave the bedding be a little bit damp. They would have the cage be sort of tilted. They'd leave them in a cage by themselves, and they're kind of a social species.

47:06So nowhere near as bad as what you're thinking. That's very gentle, yes. That is, yes. And again, as we've discussed multiple times on the show, before you do experiments like this, you need to get animal care and use protocols. And we understand you have to stress the animals out to test the hypothesis, but you've got to do it in the most humane way possible. Good, okay. But the most effective and fast method they found for stressing the animals out was to give them an injection of a capsaicin analog under their skin. So capsaicin. That's spicy? That's spicy. Yeah, that's the stuff that gives you the spicy feeling if you're eating peppers or something.

47:38So they would like internally pepper spray these mice? Yeah, you always find the most horrible way to say these things when we talk about animal studies. But I am going to just use the phrase the injection for the rest of this description. Oh, that makes you feel better, Kelly. All right. All right. Well, do you want to know the answer to this or not? Yes, I do. Please. Thank you. All right. So they inject mice with this capsaicin analog, and the mice did get gray, but they got like salt and pepper gray, like me. Oh. So it wasn't – they didn't turn completely gray. It wasn't patches. It was exactly what you would expect if you had hair follicles on random cycles and some of them started turning gray.

48:17And did they look at the microbiology of it? Like, can they see the melanocyte dying or doing something or giving up or? Yeah. So that's the next thing that they did. So next they said, OK, we know that we've got these mice that will turn gray sort of like humans do. So what's happening? So then they decided they were going to, for the stressor, they were going to just keep using this injection. So then they used the injection and they looked at what was happening with the melanocyte stem cells and with the melanocytes. And what they found was that the melanocyte stem cells were, like, disappearing.

48:48But the melanocytes were staying where they were. And so all of the melanocytes that had already been made were fine. They kept making the black pigment for these black mice, but the melanocyte stem cells were gone. So the next time a phase started again, no new melanocytes were made and those hair follicles would become gray. So gray is the default color. If you don't have a melanocyte, then it's just gray. Yes. Right. And so they're like, OK, where did these melanocyte stem cells go that are supposed to be there to make sure you've got the cells to give you color every time the cycle starts again?

49:23So that was the next question that they wanted to ask. And so one idea that's been going around for a while is that when you get stressed out, something about your immune system attacks your hair follicles and something about that makes it so that your hair goes gray. And so we've done so much work on mice in the lab now that you can just like pop open a mouse catalog and you can order mice that like have various parts of their immune systems that don't work anymore. And so they like ordered some mice that don't have T cells or don't have B cells or like they're lacking various parts of their immune cells.

49:56Meaning that there's like an industry that manufactures mice with specific deficits that are useful for scientific experiments. Yes. Yeah. Amazing. So they essentially ordered some mice who don't have like good immune systems in a variety of different ways. And they gave them these injections and they still went gray. So that was pretty good evidence that it's not something about the immune system that's important for creating this gray. So the next question they wanted to know was, OK, well, is it something about stress? And usually when you are thinking about stress, you think about cortisol or noradrenaline.

50:29So cortisol is a hormone that humans make, and we release it in times of stress. And what it does is it helps us mobilize energy. So for example, if you're being chased by a lion, you want to make sure you've got as much energy available, as many calories that you could send to your muscles or whatever, so that you can run away from that lion. It's not going to make you faster than you usually would be, but as fast as you're able to be, they want to make sure that you can be to try to get away from that lion. And then after that stressor, it tries to help your body like recover from this massively horrible thing that just happened to you.

51:04And so for us, that hormone is called cortisol. Mice have a closely related version called corticosterone. And so they wondered, OK, maybe it's something about corticosterone that causes graying. And so it turns out that the melanocyte stem cells have receptors for corticosterone. And so what that means is that these stem cells can bind to corticosterone. And what usually happens when a receptor binds to a hormone is that that hormone is sending some message to the inside of the cell that the cell needs to do something. And usually what that something is is like you need to go into your genetic blueprints and start making some new compound.

51:44Yeah. Yeah. So what they did amazingly is they said, OK, we're going to essentially take the receptors off of the melanocyte stem cells. and now we're going to inject the mice with the capsaicin analog and see what happens. And those mice still got gray hairs. So it wasn't about the glucocorticoid stress hormones because even when that hormone can't talk to the melanocyte stem cells, you still get gray hairs. Are you with me? Because this is kind of confusing, but it's beautiful how they're doing this step by step. I didn't follow glucocorticoid, but I think I do understand the argument here is that these melanocyte stem cells, the things that you need in order to make new melanocytes, are disappearing, and they have a button on their outside that responds to this stress hormone.

52:33But when they disabled that button, it didn't change anything. So they don't think that pressing that button due to stress is killing these melanocytes. Thank you. Yes, that's a great way to say it. Okay, perfect. And they have another button for noradrenaline. And noradrenaline is just another chemical your body makes when you're stressed out. but it comes from different places. It can either come from your sympathetic nervous system, so it can come from nerves that talk to your hair follicles, or it can come from these glands that sit on top of your kidneys. They figured out that if you remove this button for noradrenaline, they don't turn gray.

53:10Oh. And they figured out that the message is not coming from on top of the kidneys. The message is coming from the nerves. Oh. I'm simplifying a little bit because I realized I was getting a little too in the weeds. But anyway, it is coming from the nerves. And they were actually able to use this neurotoxin to keep the nerves from sending the message to the hair follicles. And they didn't turn gray when you messed with the nerves. So it's definitely the nerves that are sending the message to the melanocytes that is essentially making the melanocytes disappear. And what's the connection then with stress?

53:44Is something about the stress that makes the nerves send this message? Yeah. So you stress someone out. Their sympathetic nervous system, their fight or flight system is like, oh, and they release noradrenaline. And that noradrenaline binds to the melanocyte stem cells. So you're the button on the melanocyte stem cells has been pushed. But if they are in the phase where they're supposed to be sleeping, you've woken them up from their sleep and they kind of freak out. And instead of, I don't know, going back to sleep, they start doing something totally unexpected. They all start turning into other kinds of cells.

54:23I think they're turning into melanocytes. And then they migrate away. And so by the time this process is done, you don't have any more stem cells. They've all done what's called differentiated, which is a fancy way of saying they've turned into a final version of a cell and they can't make new melanocytes anymore. And then they migrate away. And so they're not there anymore. The next time your hair cycle starts again, they've wandered off for reasons we don't understand. And so something about freaking out from some stressful event totally like discombobulates your melanocyte stem cells and they wander off.

55:00So that makes sense as a mechanism to explain why this happens. But why would melanocyte stem cells have this button? Why are they sensitive to the presence of these stress hormones? We don't know. Ooh. Yeah. So there has been a connection between pigment producing cells like melanocytes and our nervous system for, you know, like a really long stretch of evolution. So, for example, octopuses and other cephalopods, if you stress them out, they will talk to their pigment producing cells to like change colors, kind of like blend in with the environment. but that doesn't explain why we have nervous systems that are like talking to our melanocytes and our hair follicles.

55:43But there is this like long connection. Maybe there's some reason why it still benefits us that we don't know. But when I read the discussion of this paper from 2020, they were pretty much like, not really clear why this is happening, like what the evolutionary benefit would be. Maybe it's something that was beneficial millions of years ago and there was just never a reason to decouple these connections. Maybe it's not so bad for people who have experienced stress to advertise that by showing off their gray flowing locks so people know, oh, you know, Kelly's been through something. Let me ask her opinion.

56:16That's what she's probably wise because she experienced. Yes, right. Grad school gave her gray hair. She can tell us to not go. No, I had fun in grad school. And so is this only something that happens in mice or is the same mechanism happen in other animals like in people? I think it happens in other animals, too. Like, I mean, dogs definitely go gray. I don't know if they go gray for stress. But, like, I think if it's happening in mice, it's probably happening in other animals, too. So I'm guessing this is a pretty common thing. And this suggests there might also be a treatment available there.

56:48You could somehow protect those myocytes so they don't get that button pressed. Yeah. So one, I want to note that it's really refreshing to have you be the one mispronouncing a word for once. I'm, like, feeling great about that. And I guess we both give as good as we get in terms of picking on each other. But yes, it does suggest that if somebody has had like a super stressful experience, maybe you could try to calm them down in some way quickly in a way that might rescue their melanocyte stem cells. You'd have to do that pretty fast because once those stem cells have migrated away, they don't come back.

57:24Yeah, then you've lost them forever. Wow, fascinating. I really appreciate this question, Joe, because this was like, this was so much fun to read about. Like, there were lots of things in this paper where I was like, I have no idea what you're saying. This is like crazy molecular biology stuff. But like, wow, this was a cool set of experiments that really like. Anyway, I am going to try to make sure nothing super stressful happens to hasten my decline into silver foxhood. But I'm sure I'll rock it either way. Well, fortunately, it doesn't sound like answering this question was that stressful for you, which is a relief.

57:56So let's send it over to Joe and hear about whether it gives him any more gray hairs. What a colorful journey to finding that association. I'd like to mention that this kind of science, where the search for an answer becomes a series of experimental steps, is research of the best kind. It's also one everyone can do in their own way. Thank you for getting to the root of this question without stressing anyone out. In the same vein as Kelly, I too have a few hairs of wisdom. That said, I'm definitely still going for the spicy foods. Whether your head is black, blonde, bare, or glistening gray, stay chill, everyone.

58:34All right, thank you very much, everybody who sent us questions. We really do love hearing from you. And one reason is that it gives us an excuse to dig into some corner of physics or biology that we always wanted to understand and never had a reason to spend an afternoon on. So thank you very much, everybody, for being curious and for sharing that curiosity with us. Thank you.

59:00Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We would love to hear from you. We really would. We want to know what questions you have about this extraordinary universe. We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you. We really mean it. We answer every message. Email us at questions at danielandkelly.org. Or you can find us on social media. We have accounts on X, Instagram, Blue Sky, and on all of those platforms, you can find us at D &K Universe. Don't be shy. Write to us. When you're a maintenance engineer in a beverage manufacturing plant, you keep production lines moving and quality on track.

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