Listener Questions #29

This is an iHeart Podcast. Guaranteed Human Beetles and fungi are decimating trees in Seattle. Do any other invertebrates ride fungi into battle? How can the ambipolar field ignore Earth's magnetic might? And why is it stronger on Venus? Could it grow here one night? Is it true that stress can turn your hair gray? My world is kind of a dumpster fire right now, so I'd prefer if it didn't, okay? Whatever questions keep you up at night Daniel and Kelly's answers will make it all right Welcome to another Daniel and Kelly's Extraordinary Universe another listener questions episode. We've done 29 of these You know, we haven't actually done 29 of these. This is the 29th We're doing the 29th of these All right, so my question for you today Kelly is when did you start to go gray? Oh man, uh, gosh Long time ago. I started getting a few Random grays towards like the end of undergrad I think and then in grad school started speeding up my mom started going gray at 18 Wow And so I kind of anticipated it would happen But I didn't realize that I was really starting to go gray until a friend of mine told me that I was quote Rocking the salt and pepper look And I gave him the stink eye because I thought of myself as someone who had a few stray grays And I hadn't realized I had transitioned to salt and pepper, but it was very nice. And so I Anyway, I've transitioned to salt and pepper apparently and uh, what about you? I can't you've got you've got some grays, right? It's hard to tell on the Rooverside camera. Um, I think I might have one or two gray beard hairs Daniel that's not fair. I know but I think I'm still pretty much all original color up top. So Wow, congratulations Daniel Yeah, well, there's some mythology in my family my grandparents on my dad's side Both had jet black hair into their 80s But there's discussion in the family about whether or not they dyed it and some people are like, oh, of course They dyed it. How naive are you to believe that an 80 year old had black hair? And I don't know maybe they did who knows. I'm not going to exhume their body and do some tests scandalous But so far in my personal experiment, no grays up top. Yeah, I'm cool I don't know. I don't really it doesn't keep me up at night that I have gray hairs like I you know I was yes, I was a little surprised but mostly it's just because I'm not very self aware But at the end of the day, like I don't care enough to dye it or anything like that I'm not losing sleep and what comes after salt and pepper before you're fully silver haired. Is there another stage there? I don't think so See So once you're past salt and pepper you're just all in I think then you're at silver fox. Oh And then you go white And then you're gandalf. Yeah, I look forward to becoming gandalf. I'll get there the white wizard Well, that's the thing is people are like, oh, you haven't turned gray yet, but I think gray adds gravitas It's nice for people to think you're younger than you are But then it also makes them take you less seriously sometimes Yeah, but something that I do want to take very seriously are the questions in the minds of our listeners because our goal is to give you a tour Of everything that's extraordinary in the universe But not just the things that we find extraordinary the mysteries that tickle your minds So if you have questions about how the universe works, please write to us to questions at danielandkelly.org Today's questions were taken directly from those messages And you'll see that daniel wasn't just gloating at the beginning of today's episode Although that might have been part of it. We did get a question about graying hair towards the end No, that was just bragging just straight bragging. There was nothing humble in there. So That's very all right. So let's move on to question one from eric and let's go ahead and hear that question now Hey there, extraordinary's eric and I had some technical difficulties So i'm going to go ahead and read his question and rest assured the answer has already been shared with eric The question is regarding the spruce bark beetle in alaska and their relationship with fungus I understand that they're born with the fungus which is parasitic to spruce trees Which knocks back the immune response of the trees to resist the beetle The beetles are a delivery mechanism for the fungus Is this relationship unique to beetles? So he spells beetle be a t le Is he talking about the insect or the rock band? Uh, I am going to go ahead and assume that that was an autocorrect because when I was going ahead and taking notes A couple times My phone and google doc's autocorrected to the band spelling. I guess the uh, the band is much more popular than the invertebrates Well, but there are more kinds of beetles the invertebrates than beetles the singers, right? So yeah, yeah many many Yes, there's I think, you know, there's probably something like 6000 bark beetle species and there's yeah far fewer beetle members And you're not prepared to answer the question if the context were rock musicians. Yeah, no, that's right I although I did just listen to uh, the rest of history did a few series on the beetles But uh, but no, I'm probably not prepared for for a whole beetles episode All right, so tell us about the bark beetles and their relationship with spruce trees Okay, so there's a lot of different species of bark beetles and some of them kill trees And recently there have been some mass tree die-offs as a result of bark beetles They're so sad. Yeah, but so you know a lot of the beetles that are causing these die-offs are native Which I think makes the story a little complicated. So for example in alaska, you have the spruce beetle It's native and usually it goes after unhealthy trees And when its population numbers are pretty low It doesn't cause a lot of trouble like it takes trees that were already kind of on the way out Maybe hastens their demise a bit, but that's not a big deal Do you mean it goes after the ones that are unhealthy like it knows or that it just has success against those? Oh good question. I don't know if it's specifically Going after the unhealthy ones or if it just is better at the unhealthy ones because trees do have something like An immune system defense And as we're going to discuss in a moment here the beetles have a fungus that helps them with that immune system defense Amazing. Yeah, but it could be so you know the beetles I don't think they're like randomly blithely going about their life not making any decisions I think they probably can to some extent tell if they are near a tree that is Going to be easier or less easy to invade And so probably they're they're searching for the unhealthy ones that they'll have an easier chance with But at high population numbers those some of those unhealthy ones might get crowded and they get pushed out to healthy ones Let's let's say that's what's happening. All right And so when they get to really high population densities and there's loads of these beetles all over the place They start killing the healthy trees too And so for example, there's been an outbreak of these beetles in alaska and something like 1.6 million acres have been impacted And that means a bunch. Yeah, many many many of these native trees native spruce Trees have been killed in alaska And there's another outbreak of the eurasian spruce bark beetle that's happening right now in europe And it's decimating the conifer forests And so, you know, as I mentioned a lot of these beetles are native and so the question is You know, like I think a lot of us are bummed out because we like forests and we like trees and living trees Living trees, right and the idea that beetles are killing a bunch of trees Stinks, but I guess the question is is this a natural process or not? So, you know, when a bunch of trees die They fall and that clears forest floor To suddenly get sunlight that wasn't getting sunlight before because the trees were blocking it and now you can get Flowers and pollinators and this is sort of how ecosystems turn over ecosystems are not usually stagnant And so I guess the the interesting question to me is Is this like a 200 year cycle and we just kind of weren't taking notes before and we're just seeing something that naturally would have happened or Would the 200 year cycle have included maybe like one hectare of trees dying But because of global climate change or because we've managed forests in a way That you know has made more trees unhealthy. Is it just way more intense than it's ever been in the past? In which case, uh, you know, maybe we care now because we have made this problem much worse than it would have been Does that make sense? Yeah, but I had the impression that some forests were truly ancient You know that forests can be fairly stable if the climate is stable, etc Then trees can grow for hundreds or thousands of years So it's not like there's a 200 year cycle where all the trees in the forest die and then get replaced and that's just what we're seeing, right? It feels like we're seeing a shift in the capacity for forests to exist Right out here in the west we see lots and lots of dead trees on hillsides and it feels like maybe we're seeing the ends of forests Well, if it's the first vote when I said 200 I probably should have said x because I was just picking a number but but uh, so I was listening to Indefensive plants which is a great plant podcast and they had a guy on there who studies bark beetles And he was saying that like, you know, we really don't know if this is a natural cycle or if it's something that's getting much worse And and we do think that probably it is a problem that has gotten much worse But for a lot of this stuff we don't have great data because if x is a thousand and it's like a thousand year cycle We probably wouldn't have great data on that Maybe every 1,000 years you do expect to see all the trees on the hillside dead And then the cycle starts again or something But it wouldn't surprise me to hear that we have made this problem worse Through global climate change and exacerbating drought and stuff like that. But let's get back to the beetles and the fungus Yes, so what are the beetles doing to the trees and how does the fungus help? Okay, so the beetles arrive at a tree and they like, you know For example, they might go under the bark and the adults might move around under the bark And when they do that they introduce a fungus and this fungus the only way it can get from like tree to tree Is it travels with the beetles? And so that's how the beetles benefit the fungus? So then the fungus infects the tree And it does a couple different things for the beetles One of the things that it does is that the tree has a bunch of chemical defenses that it would use to make the beetle sick and kill them And the fungus takes those chemicals that the tree was using to defend itself and it neutralizes those chemicals So the tree is no longer toxic to the beetles. Amazing. Totally agree. Yeah, it's crazy And now instead the beetle is starting to convert stuff in the tree to stuff that's nutritious for the beetles So now it's easier for the beetles to get nutrition from the tree The beetles aren't getting attacked by the tree In some cases the beetles are actually converting some of the things that the tree makes into pheromones to attract more beetles to the tree Wow I know it's crazy And so then the beetles lay their eggs in the tree And if you you know if you've worked with like trees before maybe sometimes you've pulled a piece of bark off And underneath you've seen all of these sort of like almost random lines that crisscross over each other Those are the paths of like little baby beetles that have hatched and sort of moved around And that's like the path of the food that they ate and the movements that they made Yeah, like these little tunnels that they've dug through underneath the bark. Yeah, it's very cool to see Yeah, they're called galleries and I do feel like they're little works of art Like I love that name for them And so anyway, this reproduction keeps happening and with this collaboration between the beetles and the fungus The beetles are able to overwhelm the tree's defenses and they can kill the tree that way And it's just something that happens to trees worldwide. This must be a common pattern between beetles and trees I remember seeing these kinds of patterns on the back of bark of like ponderosa pines in new mexico, for example Yeah, so lots of trees have bark beetles like at least one bark beetle species Sometimes you can find more than one beetle species living in different parts of trees Not all of them are Super bad for the tree and again a lot of times it depends on how many beetles there are how bad the condition of the tree is But yeah, you can find these almost all over the world It seems to particularly be a problem for like spruces and pines and stuff Is it ever good for the tree? Are they doing anything that's helpful? I didn't come across examples of that in my reading Yeah, it doesn't mean it's not out there. I didn't read every paper on bark beetles as you can imagine with over 6 000 species There's a lot of papers out there Well, I don't know why but I feel myself rooting for the trees I mean, I'm not the Lorax or anything and beetles have just as much a right to live and eat as trees do But it feels like, you know, the trees have this grandeur and they're supposed to be there and the beetles are invading whatever So give me a more ecological viewpoint on this. Why should I not be attached to the trees or should I? I think you could argue either way Like I mean I'm I'm attached to the trees and when the trees die Then the like, you know, the woodpeckers that we're living in there don't have a home anymore And like all of the other organisms that depended on those trees are in trouble Yeah, you know, I I think it makes sense that we get sort of emotionally attached to those forests and all the organisms that live in there But you know, the only constant in life is change and ecosystems do pretty regularly turn from one thing to another and so You know expecting a system to stay exactly the same Can cause problems So like one problem that humans have caused is we've tried to suppress fires because we thought well fires are bad But now we've let fuels build up Over time and now there's tons of fuel and so when you do get a fire it burns extra super hot And it kills everything whereas before there were some species that would have survived a fire that didn't burn quite as hot And so, you know, we kind of mess things up when we tinker with it So the question is should we tinker with this bark beetle situation? And can we tinker with this bark beetle situation? Like what could you even do? They're living under the bark and like, you know, what can you do that would target the beetles? Or their fungus without messing with the rest of the ecosystem? Like it's a really tough problem And I don't want to make it sound like I'm saying we should throw up our arms and not do anything ever But just that, you know, these are complicated problems that you need to think about from multiple angles Yeah, and I definitely have emotional connections to some parts of the ecosystem You know, like anything that threatens my children, for example You know, I'm not just going to be like that. It's in the way of coyotes to tear out the throats of my children Like, you know, I'm definitely stepping in there and doing something I'll note that um That one, uh, we got an email from pita encouraging us to uh think about things from the animal standpoint a while back And when I moved out to the middle of nowhere, I did do a lot of research on whether or not it was safe to let my like Three-year-olds outside with coyotes. I was outside with my three-year-olds And it is very rare for a coyote to go after a three-year-old But you are encouraged to stay with your three-year-olds outside if there's coyotes around But once they get bigger, uh, the coyotes are very unlikely to go after them. So you are children Are safe from coyotes at this age. I would suspect I hope that's true Just two days ago My daughter called me because she was out walking our dog and there was a coyote that blocked her on a path And she was like, I don't know what to do So I biked over there and made my presence known. Oh wait, and so you had to scare the coyote away? Yeah, oh wow Yeah, they are very brazen in our neighborhood now. They they roman packs. They're everywhere and hey, you know, we moved into their neighborhood So on the other hand, I don't really want them eating my kids or my dog. Yeah, but back to the question at hand We're talking about fungi and beetles one question I had is these beetles are using the fungus to help colonize the tree What's in it for the fungus and what's happening when the beetles are not in a tree or are the beetles never not in a tree The beetles are pretty much always in a tree or moving from one tree to another and the fungus get transport So the best way for the fungus to get from one tree to another is by being moved by the fungus That's the main thing we think that they get from it. Okay, and are beetles the only ones who do this kind of fungus farming? No, really? Yeah, so eric wanted to know, you know, what other invertebrates collaborate with fungi And uh, it turns out that there's quite a few invertebrates that collaborate with fungus And so fungus farming is a pretty common thing in the invertebrate world Daniel, I have a question for you termites You look at termites. Yeah, what do you think termites are closely related to if you had to guess? Termites or do you already know the answer to this? I do not know the answer Okay, they're an insect because of the legs. They got all those little segments. They seem kind of anti to me Thank you. Yes, they do look anti to me And I and so I said something to one of my friends about them being you know, kind of ant like and they were like Kelly They're more closely related to cockroaches What? Oh, no, and I looked at them for a second and I kind of gave them a little bit of the stink eye because I was like You are either messing with me or I should be very embarrassed Because I am way off here and it turned out I was way off. Well, I don't have to be embarrassed because I'm not supposed to know So Well, yeah, I wasn't trying to embarrass you like you were trying to embarrass me about my gray hair earlier, but Ooh slice I'm impressed by the gravitas your gray hair lends to you. Oh, thank you. Yes. I look very mature and commanding of wisdom and whatnot All right, so fungus farming is seen in some termites ants wood wasps and Ambrosia beetles. So basically the deal here is that they collect certain kinds of fungus They put fungus in a certain area sometimes For example, there are like leaf cutter ants who will feed the fungus certain kinds of leaves And then the fungus will break it down into things that are more digestible for you know, for example the leaf cutter ants So let's talk about the ambrosia beetles for a second So the ambrosia beetles will farm fungus and they will bring them into for example, like uh dead Trees and then they'll create those galleries that we were talking about and they'll sort of lay their eggs They'll have their babies and the fungus will be like creating food for everybody And the ambrosia beetles even have little specialized parts on their body so that they can carry the fungus with them From one place to another and so this is like a very close symbiosis So they can you know can bring it from one place to another But while I was reading about this I discovered a cool concept called myco kleptism And so well some Ambrosia beetles will bring the fungus with them from place to place and will essentially live with the same strains of fungus for their whole lives Other beetles will steal fungus from others And so there are some beetle species who will find an ambrosia beetle who's doing a good job of farming their own fungus They're being good farmers good stewards of the land and then the myco kleptics Will uh will come in and they'll steal some of the fungus and they'll start farming it on a different part of the log Kind of close by they'll lay their own eggs in there And they'll essentially steal the fungus and so they don't They're not born with this fungus. They take it from another organism over the course of their lives Wow, that's a little creepy. It's a little creepy. Yeah. Yeah, it's like your family stealing beans from another family or something, you know Because you guys have a close symbiosis with beans and chia seeds That's true. We do we are lovers of fermented foods and fiber over here Mm-hmm The people of britain love their fancy blenders They bought loads of them and luckily if they bought them with barkley card They earned rewards. In fact, they'll earn rewards on all their eligible purchases It's a more convenient way to consume your fruit and veg What you buy is your business giving you rewards on purchases is ours Barkley card backing your future 28.9 apr representative variables subject to application financial circumstances and borrowing history teas and seas apply Okay, 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 gonna be talking about gray hair salt and pepper silphre foxes later? Oh, yeah, okay. We're back. We're back Oh, yeah, okay. We're back. We're back to my gray hairs. We're gonna 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 them No, no, you're not you can't walk back The problem you started earlier today daniel All 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 ambi polar 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 It's like having a tin 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 ambi polar field Right, so i'm thinking about ambidextrous and you can switch between left and right Is that is that helping me understand ambi polar because it can it's 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 and that's what holds the atmosphere in place For example or earth's magnetic field magnetic fields are generated by charges in motion So with that 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 ambi polar field is something completely separate from both of those Is 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 no, but a little bit. Yeah a little bit So what happens is if you have a neutral particle like 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 So 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 That is an electric field the ambi polar field In the upper atmosphere of earth and also mars and also venus. So that's what the ambi polar 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 or anything, but it's kind of cool. Okay. Yeah needs and you could also in principle Use it to help like steer satellites You know, uh, this one way to steer satellites instead of having Thrusters you still 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 you so earth Mars and venus have it. All right. So whatever they are so they all have gravity, but every planet has gravity They all have atmospheres So you need an atmosphere although mars's 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, right? 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 has a very dense atmosphere. So there's a lot of electrons and ions to pull apart But also because venus has no magnetic field 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, etc Hitting the upper atmosphere that's 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 And 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 the 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 electric magnetism 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. Yes, 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 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 it might have had internal motion which generated a magnetic field Which shields 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 What seems unlikely? I mean, we don't really understand it and 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 gonna burp at us some huge blob of plasma That comes and strips away a lot of the atmosphere or ionizes it that could happen any moment You know, just a few weeks ago. We had really strong aurora boreal eye. Is that how you pluralizing? 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 let's hope it doesn't happen All 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 the way 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, by the way, my spare room is still available for professors if you're ever in the north of england Thanks for a great show Giga clear goes further than any other major provider to bring you fast reliable whole home coverage with free expert wi-fi installation We come in we set up we do it all for you. So you don't have to it's not rocket science It's installation science Switch to giga clear from only 16 pounds a month faster rob dan for rural brick 18 month contract prices may vary verify at giga clear dot com I 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 and our kids have expressed their Hmm 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 great 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. All 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, you know 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 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. You 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 Anagen 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 anagen. What happens is that you have hair follicle stem cells and 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 Cool 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 anagen 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 because 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 coating 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 46 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 and at this stage the melanocytes Die, but your melanocytes 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. Okay. And then you go into a resting phase and this can last for a few months where the hair follicles 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 and 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 is started and after the new melanocytes are 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 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 You know, I was thinking maybe it was like probabilistic and hair was 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 the 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 hair is on your head But 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 keeping mind. It's in mice Not in humans, but okay. So first they say If you stress out black mice, will they get gray hairs? So they stress mice out a couple different ways and the mice do start going gray. Are they terrible? Uh, 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 like put it in a cage next to a cat Not to kill it, but just to like put it in the cage next to it. That would be pretty stressful for a mouse Oh, okay. So no, this is nowhere near that bad actually So they they would rapidly change the light and dark cycles. They would leave the bedding be a little bit damp They would uh, have the cage be sort of tilted They'd leave them in a cage by themselves and they're kind of a social species So nowhere near as bad as what you're thinking. That's very gentle. Yes. That is yes Yeah 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 So 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 uh, I am going to just use the phrase the injection for the rest of this Description if 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 uh gray But they got like salt and pepper gray like me So it wasn't they didn't turn completely gray. It wasn't patches It was exactly what you would expect if you had Heropholicals on random cycles and some of them started turning gray and 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, okay We know that the we've got these mice that will turn gray sort of like humans do so what's happening So then they they decided they were gonna 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. Oh, but 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 heropholicals 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, okay. 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 So 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 like heropholicals 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 meaning that there's like an industry that Manufactures mice with specific deficits that are useful for scientific experiments. Yes. Yeah 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 okay Well, is it something about stress and usually when you are thinking about stress you think about uh, cortisol or noradrenaline so cortisol Is a hormone that humans make and we've released it in times of stress And what it does is it helps us like 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 you know as many like 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 stresser it tries to help your body like recover from this massively horrible thing that just happened to you And so for us that hormone is called cortisol Mice have a closely related version called corticosterone And so they wondered okay, 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 Yeah, so what they did amazingly is they said Okay, 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 But 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 like glands that sit on top of your kidneys They figured out that if you remove this button for noradrenaline They don't turn gray And they figured out that the message is not coming from on top of the kidneys. The message is coming from the nerves 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 like use this neurotoxin To keep the nerves from sending the message to the hair follicles And they didn't turn gray when you like 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? Is something about the stress that makes the nerves send this message? Yeah, so you stress someone out. Mm-hmm. Their sympathetic nervous system, their fight or flight system is like And they've released noradrenaline And that noradrenaline binds to the melanocytes stem cells So you're the button on the melanocytes 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. I think they're turning into melanocytes And then they migrate away. And so by the time this this process is done You don't have any more stem cells. They've 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 like 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 melanocytes stem cells and they wander off So that makes sense as a mechanism to explain why this happens But why would melanocytes stem cells have this button? Why are they sensitive to the presence of these stress hormones? We don't know 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 But there 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. That's what she's probably wise Because she experienced. Yes, right grad school gave her gray hair. She can tell us to not go Uh 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 I 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 You 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 you know, we both give as good as we get in terms of picking on each other but 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. There's they don't come back Yeah, 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 I 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 fox hood 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. So 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 bear or glistening gray Stay chill everyone. All 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 Daniel and kelly's extraordinary universe is produced by iHeart radio. 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