Speaker 1: Hey, everybody, it's your old pal Josh for this week's select.
Speaker 1: I've chosen Does the body replace itself every seven years?
Speaker 1: Sounds like a medical episode, and it kind of is.
Speaker 1: But after a little while it turns into a brainbuster
Speaker 1: of a head scratcher of a philosophical bent that I
Speaker 1: think you're gonna love. I hope you enjoy the living.
Speaker 2: Heck out of it.
Speaker 3: Welcome to Stuff you Should Know, a production of iHeartRadio.
Speaker 1: Hey, and welcome to the podcast. I'm Josh Clark with
Speaker 1: Charles W. Chuck Bryant and guest producer.
Speaker 2: Nol Knowle's in the house.
Speaker 1: It's the it in the new studio. Yeah, man, this
Speaker 1: place is comfy, cozy. I like it.
Speaker 3: I wish I'm I don't know, I wish there was
Speaker 3: a chair version of a waterbed.
Speaker 1: I know this is a napish little place.
Speaker 3: Yeah, especially today, I think I'm dragging all apologies.
Speaker 1: Yeah, same here. So if we're talking kind of slow
Speaker 1: or low, or we just stopped talking for a little while,
Speaker 1: it's we're as tired.
Speaker 2: Yeah, bumped into you at the Hawks game last night.
Speaker 1: I know, Hey, how many is that?
Speaker 2: You know? Yeah, just at the bump in yep.
Speaker 1: We were both at the Hawks gaming and the Hawks.
Speaker 3: One didn't even know we were going. Look over in line,
Speaker 3: there's Josh and Yumi. Yeah that's great. There's Chuck and Eddie.
Speaker 3: Yep in an arena of eighteen thousand bumping into someone?
Speaker 2: Is that it?
Speaker 1: That's all it holds?
Speaker 2: I think it's something like that. It's a good lot
Speaker 2: of people.
Speaker 1: It's a good arena.
Speaker 2: Yeah. But you had box seats because you're special.
Speaker 1: They were free out.
Speaker 2: Mine were free to in. The nose bleeds.
Speaker 1: I liked just about every seat in that place.
Speaker 2: Yeah, it's not too bad. I was.
Speaker 3: I was laughing about the nosebleeds going in, But then
Speaker 3: I got up there.
Speaker 2: I was like, this is great. Yeah you can see everything.
Speaker 1: Did you nose actually bleed just twice?
Speaker 3: Yeah, once out of its sheer excitement and then once
Speaker 3: from the altitude and that was more of a spray,
Speaker 3: rightah yeah.
Speaker 1: Just covering everyone that was like go Hawks.
Speaker 2: Boy, what a weird intro.
Speaker 1: It's a little weird, but I mean it kind of
Speaker 1: jibes a little bit because we're talking. Yeah you're mentioning blood.
Speaker 2: Sure, it was shedding cells and blood.
Speaker 1: You were like, blood is made up of cells and
Speaker 1: we shed tons of cells. But before we get to that, right,
Speaker 1: there's the fact that the podcast you shed cells. I
Speaker 1: want to mention this one thing I read. Yeah, it's
Speaker 1: called I think the title of the article is the
Speaker 1: Self is Moral. It's about like where we get our
Speaker 1: identity of self from, like where it's rooted. It was
Speaker 1: written by a person named Nina Stromyer. I believe it
Speaker 1: was on AON magazine. Yeah, just type in the self
Speaker 1: is Moral aon it'll come up.
Speaker 2: I'll get you there.
Speaker 1: Uh. And towards the beginning, the author says, there's this
Speaker 1: very famous philosophical exercise, which you know, philosophers love to do,
Speaker 1: like mental exercises.
Speaker 2: Yeah, that's what that's all they hashened.
Speaker 1: So imagine you have like a kind of imagine you
Speaker 1: have like a ship, right, like a boat. Yeah, a
Speaker 1: nice Yankee clipper, okay, okay. And this Yankee clipper is slowly,
Speaker 1: over time kind of salvage for parts. But rather than
Speaker 1: just being stripped, like every time a part is taken out,
Speaker 1: it's replaced, and then over the course of like fifty
Speaker 1: one hundred years, is each plank, as each bolt, as
Speaker 1: each like mast head, even the thing. The carved lady
Speaker 1: in front eventually just gets replaced with something else.
Speaker 2: Yeah, a new carved lady that speaks of the time.
Speaker 1: Right, you know? Is it still though, after every single
Speaker 1: part has been replaced, the same ship that it was before?
Speaker 2: Yeah? I see what you mean. I don't think that
Speaker 2: can be possible.
Speaker 1: Why not, especially if it has the same name and
Speaker 1: it's the same ship in the same place as before.
Speaker 1: It was just slowly, over time moved out. True, where
Speaker 1: does the self lie?
Speaker 3: Yeah, that's a good point, man, Like redoing a house,
Speaker 3: same thing, Yeah, I mean, like they saw the floors
Speaker 3: and the walls and the windows, Like, when does it
Speaker 3: cease to become that same house that was built in
Speaker 3: nineteen thirty exactly.
Speaker 1: Isn't that cool?
Speaker 2: Yeah? It is really cool.
Speaker 1: And the reason that it applies to this episode is because,
Speaker 1: over the course of your lifetime, a significant portion, pretty
Speaker 1: much all of the cells in your body are going
Speaker 1: to be replaced. Yeah, so that the person even after
Speaker 1: you reach your adult self. Yeah, physically, by the time
Speaker 1: you die, assuming you're gonna die much later, you are
Speaker 1: essentially a different person, at least on the cellular level.
Speaker 2: Yeah, thirty seven trillion cells.
Speaker 1: Ish that's how many we have.
Speaker 2: Yeah, that's what they estimate. And I did a little
Speaker 2: looking into.
Speaker 1: Lifespans, like an estimate.
Speaker 2: Thirty seven trillion. Yeah, what do you want like to
Speaker 2: like give or take?
Speaker 3: Yeah, I did a little research into lifespans just because
Speaker 3: this all sort of comes back to like your death basically,
Speaker 3: because that's all death is, is your your cells, you know,
Speaker 3: dying little by little.
Speaker 1: Well yeah, I mean if you think about it, Chuck,
Speaker 1: one of the things that.
Speaker 2: Like why do we die?
Speaker 3: If our we'll get to all that, Oh okay, but
Speaker 3: it's intriguing, you know it is it started, you know,
Speaker 3: questions started popping up. So apparently we gained about three
Speaker 3: months every three months of life humanity every year that
Speaker 3: we progress.
Speaker 1: Like the average life span spans by three months.
Speaker 3: Yeah, Like if you were born in twenty twelve, the
Speaker 3: average lifespan is now and this is the United States,
Speaker 3: is seventy eight point eight. If you were born in
Speaker 3: nineteen oh one, it was about forty seven and fifty
Speaker 3: years for men and women respectively. But if you look
Speaker 3: at the ratio, it's still about three months. Despite all
Speaker 3: our technologies, three months a year, every year, every year.
Speaker 1: Just slowly creeping along.
Speaker 3: Yeah, because I think the article it was like when
Speaker 3: we're going to live to be one hundred by average,
Speaker 3: and they say by the year twenty one hundred, if
Speaker 3: things hold, then the average human or American will be
Speaker 3: about one hundred years old.
Speaker 1: I thought that, so I guess that will if things
Speaker 1: are steadily progressing. I had heard that like our generation
Speaker 1: would be either the last or the first, the last
Speaker 1: to not hit triple digits or the first two on average. Yeah.
Speaker 3: Yeah, I guess these are all gases, you know, so
Speaker 3: who knows. Plus if you believe in like things speeding science,
Speaker 3: speeding up?
Speaker 1: Yeah, what is that? Moore's law?
Speaker 2: Yeah? Is that it? Yeah, applied to computers, so in
Speaker 2: that case.
Speaker 1: Right, right, but I mean you cantend it other stuff.
Speaker 3: Yeah, then you might think, you know it's it's but
Speaker 3: you know, they say it's not increasing like that.
Speaker 2: No, at least not so far.
Speaker 1: Moore's law is exponential growth just adding three months every
Speaker 1: year's yeah, non exponentials geometric. I think we're still at
Speaker 1: non exponential growth definitely. Yeah, we're just adding three months. Yeah,
Speaker 1: it's not bad though, that's pretty good average every four years.
Speaker 3: It's an extra year, yeah, well, and it's interesting to
Speaker 3: think about. You know, people that were born you know,
Speaker 3: a lot of our colleagues like eight years behind us,
Speaker 3: are going to live an average of.
Speaker 2: Two years longer.
Speaker 1: Yeah, that seems unfair, sad.
Speaker 2: Yeah, I know, what did they do to.
Speaker 1: Observe that we're we're thinking about our own deaths today? Yeah,
Speaker 1: and chuck that there's this rumor theory, legend maybe okay,
Speaker 1: that your body regenerates itself ninety percent of your body
Speaker 1: regenerates itself every year.
Speaker 2: Yeah that's not true.
Speaker 1: No, it's not true, but it was a very long
Speaker 1: standing rumor, and it was actually based on science. Yeah,
Speaker 1: you know, not just the idea that, oh yeah, ourselves regenerate.
Speaker 1: So back of the envelope estimate is that, you know,
Speaker 1: we regenerate ninety five or ninety eight percent of ourselves
Speaker 1: every year. It was early experimentation by injecting radioactive isotopes
Speaker 1: into human beings, yeah, and then following their course and
Speaker 1: then making estimates based on that led to this idea.
Speaker 3: It's called pulse labeling, is it. It's like tagging an
Speaker 3: animal in the wild basically.
Speaker 1: Right, but you're just tagging a cell.
Speaker 2: Yeah.
Speaker 1: The specific types of cells.
Speaker 3: Yeah, they don't do that to humans anymore. No, it's
Speaker 3: very animals. I think it's a very dumb thing to do.
Speaker 2: Sure, injecting radiation exactly.
Speaker 3: Yeah, unless, of course, you know it's radiation treatment that's true,
Speaker 3: which is still a really weird thing if you think
Speaker 3: about it.
Speaker 1: It's Yeah. I have a feeling it's gonna be like
Speaker 1: one of the things we look back on.
Speaker 2: As like a primitive treatment. Yeah, yeah, yeah, I hope so.
Speaker 1: But there was this long standing science for decades or
Speaker 1: this idea, scientific idea that we regenerated ourselves by ninety
Speaker 1: five ninety eight percent. Finally, and I think two thousand
Speaker 1: and five there was a a researcher named doctor Jonas Friesen.
Speaker 1: He's Swedish.
Speaker 2: Dude's awesome.
Speaker 1: He said, this whole urban legend is really bringing me down.
Speaker 1: I want to figure out a way to really track
Speaker 1: how often the human body regenerates itself.
Speaker 3: Yeah, and the biggest question has been the brain, specifically
Speaker 3: the cerebral cortex and the heart and the heart muscles.
Speaker 3: I mean, they want to know all this stuff, but
Speaker 3: those were the two biggest mysteries.
Speaker 1: I think, right, there's still the mysteries, but if you
Speaker 1: went back to prior to two thousand and five, in
Speaker 1: doctor Friesan's research, it was all a mystery. Yeah, he
Speaker 1: figured out. He basically put a very act curate time
Speaker 1: stamp on how often human tissue and human cells regenerate themselves. Right,
Speaker 1: So the way he did this is very clever. For
Speaker 1: a long time, botanists knew that the trees around the
Speaker 1: world contained a spike of carbon fourteen radiation.
Speaker 2: Yes, thanks to humans and nuclear bombs.
Speaker 1: Exactly from nineteen fifty four to nineteen sixty three, tree
Speaker 1: rings for tree growth around the world show a big
Speaker 1: spike in carbon fourteen. Carbon fourteen is naturally occurring too,
Speaker 1: So like just cosmic rays from the sun bombarred Earth's
Speaker 1: atmosphere and create radioactive isotopes by knocking electrons from particles
Speaker 1: in Earth's atmosphere, right, those radioactive particles become carbon fourteen,
Speaker 1: which is radioactive, and in the atmosphere, carbon fourteen binds
Speaker 1: to oxygen and creates carbon dioxide, which comes to Earth.
Speaker 1: Every living thing breathes this stuff in, whether it's a plant,
Speaker 1: whether it's a human like we just have see fourteen
Speaker 1: in our bodies.
Speaker 3: We also eat plants exactly contain the sea fourteen besides
Speaker 3: breathing it in.
Speaker 1: And we also eat the animals that eat the plants
Speaker 1: that in just see fourteen. Right, So like we got
Speaker 1: carbon fourteen in our bodies, that's right. But because of
Speaker 1: the spike in carbon fourteen that was introduced to the
Speaker 1: atmosphere from nuclear testing, there is a spike in humans
Speaker 1: as well. So you can roughly age like a human
Speaker 1: compared to another human if they were born in say
Speaker 1: nineteen fifty nine, and one who was born in nineteen
Speaker 1: seventy after there was that spike of carbon fourteen had
Speaker 1: gone away. Right, that's pretty cool. But what doctor Friesen
Speaker 1: did is even cooler. He basically went back to those
Speaker 1: tree trunks, those tree rings that show a spike in
Speaker 1: carbon fourteen, and created a calendar of carbon fourteen decay
Speaker 1: and basically said, okay, on this date, this is how
Speaker 1: much carbon fourteen was on Earth. And if I take
Speaker 1: this cell and compare it, knowing that carbon fourteen decays
Speaker 1: at a constant rate, I can tell you exactly how
Speaker 1: old this cell is exactly. And he used it to
Speaker 1: date cells and tissues and all sorts of cool stuff.
Speaker 3: Yeah, he was He went looking for a marker, and
Speaker 3: he found one due to our atomic testing program, which
Speaker 3: is pretty weird. You just released all that junk in
Speaker 3: the atmosphere and now all these years later it has
Speaker 3: a nice use.
Speaker 1: Yeah, you know it does.
Speaker 3: So we now know when we're going to die, right
Speaker 3: sort of. And the reason he was able to use
Speaker 3: this as a marker, Chuckers, is that when you take a.
Speaker 1: Breath of life, your first breath of life, that's right,
Speaker 1: and you get some you get some of that C
Speaker 1: fourteen into your DNA, and a steady amount stays in there,
Speaker 1: like you don't keep ingesting C fourteen as far as
Speaker 1: I understand, as far as your DNA goes, Oh okay,
Speaker 1: once it's in your DNA, as your cells divide, that
Speaker 1: original amount becomes divided evenly. So the less C fourteen
Speaker 1: that's in tissue, the older that cell line is. Where
Speaker 1: then the younger the actual cells are. Right, Is that right?
Speaker 3: I think so, which would mean the new cell the
Speaker 3: marker would be a fresh batch of the C fourteen.
Speaker 1: No, it have less C fourteen.
Speaker 3: Oh really, yeah, let's say you have because the cell divided, yes, exactly, Yeah.
Speaker 1: Like you have ten grams of C fourteen, which you don't.
Speaker 1: I can't imagine what that would be. Like. Let's say
Speaker 1: your your one cell that's never divided has ten Yeah,
Speaker 1: when it into two, it's each of those two cells
Speaker 1: is going to have five grand and then two and
Speaker 1: a half, and then one point seventy five and so
Speaker 1: on and so on. So since you know that C
Speaker 1: fourteen is generated at a constant rate, you know that
Speaker 1: it decays at a half life of fifty seven hundred
Speaker 1: and thirty years, you can look at the amount of
Speaker 1: C fourteen and then also the decay of it as well. Yeah,
Speaker 1: you can date things that are no longer living too,
Speaker 1: to see when the when they ingested that C fourteen.
Speaker 3: Was Yeah, he's a little like a bingo card. He
Speaker 3: just from the calendar that he made with the trees,
Speaker 3: and he holds it up in the light, and that's
Speaker 3: how he determines it.
Speaker 2: It's not true.
Speaker 3: But what he did determine though, was which is really cool,
Speaker 3: And this is sort of what we've been building toward,
Speaker 3: is that most of your cells are about seven to
Speaker 3: ten years old, yes, in the body, and there are variances,
Speaker 3: and of course we're going to talk about all that,
Speaker 3: and right after this break, we're going to give you
Speaker 3: a little primer on cells.
Speaker 2: So you know what all this means.
Speaker 3: Right, All right, Josh, were promised to sell primer, and
Speaker 3: we like to deliver on those promises.
Speaker 2: Here stuff you should know.
Speaker 3: So I guess we started off by saying there are
Speaker 3: thirty seven trillion cells about in the human body. Yeah,
Speaker 3: give or take, give or take, and water makes up
Speaker 3: about two thirds of.
Speaker 2: The weight of those cells. Oh yeah, that's right. They're tiny.
Speaker 3: You need a microscope to see them, and it's like
Speaker 3: it's the tiniest thing that can still reproduce.
Speaker 2: Yeah.
Speaker 3: And even though we have many different kinds of cells,
Speaker 3: I think two hundred types, and within those cells there
Speaker 3: are differences, but there are a lot of similarities with
Speaker 3: all cells in their structure. Namely, they have a cell membrane,
Speaker 3: they have a nucleus, have a nucleus, some have more
Speaker 3: than one. And these membranes are what allows nutrients to
Speaker 3: pass in and out, waste to pass out water through
Speaker 3: osmosis travels in reverse, osmosis travels out.
Speaker 1: Yeah.
Speaker 3: And what else, We got your mitochondria as well. That's
Speaker 3: where this is the important, really important thing, which is
Speaker 3: basically what keeps your cells alive.
Speaker 1: That's the power center, right.
Speaker 3: Yeah, and that's you know, your cells need food to
Speaker 3: live just like your body does. But you can't pass
Speaker 3: that that hamburger straight into your cell, right. It needs
Speaker 3: to be broken down so your cell can use.
Speaker 1: It exactly into what adenosne triphosphate ATP is like the
Speaker 1: universal cell fuel, right.
Speaker 2: Yeah.
Speaker 1: So there's a lot of stuff that the body does make.
Speaker 1: I think you need like twenty three I think you
Speaker 1: need twenty three amino acids, and like nine of them
Speaker 1: your body doesn't really manufacture. So those are the nine
Speaker 1: non essential amino acids, right. And you use amino acids
Speaker 1: to build proteins, and use proteins for everything from making muscles,
Speaker 1: to making red blood cells to you're mounting and immune response.
Speaker 1: Proteins are very very vital in some of them you
Speaker 1: have to build by eating stuff from your environment, right.
Speaker 2: Yeah.
Speaker 1: So you go out and you find yourself a nice
Speaker 1: pig and you cut off its back leg. You say, sorry, pig,
Speaker 1: here's a pig leg for you. But I need this leg.
Speaker 1: I'm gonna eat this leg. And what I'm really eating
Speaker 1: is the muscle. What I'm really really eating is the glutamine. Yeah,
Speaker 1: and in my body's going to take this glutamine. It
Speaker 1: can make it itself. But it doesn't hurt to have
Speaker 1: an extra little bit of glutamine.
Speaker 2: Yeah, it does to have that pig leg And you're
Speaker 2: exactly right.
Speaker 1: So I'm chomping on the pig legs. The pigs must
Speaker 1: and listeners by the way, right, just use your imagination
Speaker 1: for a second. Sure, And yes, I'm sorry too. So
Speaker 1: you're eating the pig like and you're gaining this glutamine
Speaker 1: as a result, and your body's metabolizing the glutamine and
Speaker 1: then reusing it, right, And it can be glutamine, it
Speaker 1: can be anything. If we're ingesting a protein, if we're
Speaker 1: ingesting amino acids, if we're eating any kind of food, sugars, whatever,
Speaker 1: our bodies break it down into its constituent parts, and
Speaker 1: then a lot of those constituent parts become part of
Speaker 1: our bodies. So if you think about it in this sense,
Speaker 1: when we eat, when we breathe, we're taking in stuff
Speaker 1: we need from the environment, and that stuff that we
Speaker 1: take in from the environment becomes a part of us
Speaker 1: literally physically on the molecular level, it becomes a part
Speaker 1: of us.
Speaker 2: For better or worse, depending on what it is. Of course.
Speaker 1: Yeah, that's a great I think that's ultimately one of
Speaker 1: the side lessons of this whole thing is we should
Speaker 1: take care of ourvironment because that environment becomes us and
Speaker 1: we either suffer or thrive as a result of it.
Speaker 2: You ever heard the expression you are what you eat?
Speaker 1: Exactly?
Speaker 2: Know, you literally are what.
Speaker 1: You eat, quite literally. And then also chuck, it goes
Speaker 1: the other way as well. When we excrete waste, when
Speaker 1: we exhale CO two that's taken up by other things
Speaker 1: in the environment, is deposited into the environment and it
Speaker 1: becomes part of the environment itself. So not only do
Speaker 1: we regenerate our cells, regenerate tissue on average seven to
Speaker 1: ten years, become almost wholly a new version of ourselves.
Speaker 1: Were also the boundary between us and the surrounding environment
Speaker 1: is really nonexistent because there's a constant exchange of molecules.
Speaker 3: Yeah, we lose on average, they say nine the average
Speaker 3: adult male loses ninety six million cells per minute, But
Speaker 3: we also replace those at the rate of ninety six
Speaker 3: million per minute, yeah roughly.
Speaker 2: Yeah. Yeah, so that's the good news.
Speaker 1: So we've got all these cells that we're losing. We've
Speaker 1: got all these new cells that are replacing them. And
Speaker 1: I think, like you said earlier before the break, that
Speaker 1: these the different types of cells and then hence different
Speaker 1: tissues regenerate at a different rate, right.
Speaker 3: Yeah, And they all have specialized jobs, and the cells
Speaker 3: are often built in such a way to aid that
Speaker 3: job physically, you know, different to make that job easier.
Speaker 2: Which is really cool too, right, shows how versatile they are.
Speaker 1: Yes, you know, like stem cells are very versatile.
Speaker 2: Super.
Speaker 1: So let's say your skin, Yeah, your skin regenerates every
Speaker 1: two to four weeks. I think, yeah, exactly, you get
Speaker 1: a new healthy coating of skin every two to four
Speaker 1: weeks because you're epithal cells are particularly good at regenerating themselves.
Speaker 3: That's right, And that is well, I guess that would
Speaker 3: fall on the low side, obviously, if we're talking seven
Speaker 3: to ten years. On the super low side, you have
Speaker 3: the cells that line like you're intestine in your gut,
Speaker 3: and those things don't last long at all because it's
Speaker 3: such a harsh environment. You know, you wouldn't expect them
Speaker 3: to last like weeks and months and years.
Speaker 1: I think, how long is it? Five days?
Speaker 2: Yeah, that's nothing but the.
Speaker 1: Structure of your guts that are beneath that membrane lining
Speaker 1: that turns over five days. They last about fifteen years.
Speaker 3: Yeah, it's such a like a beautiful, elegant system. Yeah,
Speaker 3: that we have right to keep us alive. Red blood
Speaker 3: cells last about one hundred and twenty days. But then
Speaker 3: you have things like cells in your bone which actually
Speaker 3: regenerate as well, so your bones are over time, over
Speaker 3: a much longer period of time, actually becoming I mean,
Speaker 3: I hate to call them new bones, but they kind
Speaker 3: of are, you know.
Speaker 1: Well, yeah, I mean compare if you took your femur
Speaker 1: and somehow compared it to your femur when you were
Speaker 1: fifteen years old, Like, they are two totally different bones.
Speaker 1: Even though they're your bones. They were in the same place,
Speaker 1: growing in the same person with the same DNA. There's
Speaker 1: still different bones because they're made of different cells. Ten
Speaker 1: years or so for the bones, yeah, something like that.
Speaker 1: For the human skeleton, three hundred to five hundred days.
Speaker 1: For the liver, very important organ it is. And one
Speaker 1: of the other cool things about the liver is it's
Speaker 1: just gangbusters that regenerating itself. You can apparently cut out
Speaker 1: ninety five percent of a person's liver, and it will
Speaker 1: grow back, and you won't have full function, but it
Speaker 1: will function, and you'll survive with just five percent of
Speaker 1: your liver.
Speaker 2: It's pretty amazing, actually.
Speaker 1: Yeah, because it will just grow right back, kind of
Speaker 1: like a hornet's nest.
Speaker 3: Interestingly, the inner lens cells of your eye form and
Speaker 3: your embryo and basically don't change. Yeah, now, is that
Speaker 3: why you have suffered from degeneration and vision?
Speaker 1: That's what I would guess.
Speaker 2: Is that the reason?
Speaker 1: Yes, so the reason so with the corneal lens, Chuck.
Speaker 1: When you're when you're born, when you're conceived, right, you
Speaker 1: are a cell of coross that divides. Finally, once that
Speaker 1: first division takes place, those corneal cells, they're set in stone.
Speaker 1: Like your corneal cells are as old as you are,
Speaker 1: same age as you. Other cells that make up different
Speaker 1: parts of the eyes they're far newer. But your corneal cells,
Speaker 1: your cerebral cortex cells, they think.
Speaker 3: Yeah, that's the one I mentioned. The brain and the
Speaker 3: heart muscles, those are the two big ones. Because obviously
Speaker 3: the reason we have diseases like Alzheimer's and dementia are
Speaker 3: because the cerebral cortex has long a thought to not
Speaker 3: regenerate cells at all.
Speaker 1: Yeah.
Speaker 3: Now I think they believe that they do in a
Speaker 3: very small number.
Speaker 1: Or different reasons, like the old factory bulb supposedly does. Yeah,
Speaker 1: in the hippocampus, so we can learn new things. Their
Speaker 1: sense of smell can be refined over time.
Speaker 3: Yeah, And I think isn't that also the reason the
Speaker 3: smell is very much tied to your memory, probably like
Speaker 3: a smell can conjure up a memory more clearly. Yeah,
Speaker 3: but the cerebral quartets itself, they don't think.
Speaker 2: Who was her name?
Speaker 3: Elizabeth Gould of Princeton did a lot of work on
Speaker 3: this because it was just basically set in stone for
Speaker 3: years like, no, it doesn't happen. And she did a
Speaker 3: lot of work over the years trying to prove that
Speaker 3: it did using tracer studies. And I think that where
Speaker 3: they are now as they think it does.
Speaker 1: Some yeah here there, here there.
Speaker 3: But obviously we still have to mention Alzheimer, so it's
Speaker 3: not it doesn't regenerate like the rest of the body,
Speaker 3: not even close.
Speaker 1: Yeah. Alzheimer's also maybe produced I guess by plaques and
Speaker 1: member plaque build up in between your neurons that keep
Speaker 1: them from firing as well.
Speaker 3: Yeah, that's it seems like we're so close to figuring
Speaker 3: out the secret, you know. Yeah, to uh, I don't
Speaker 3: know about not dying ever. I'm not talking immortality, but
Speaker 3: living much longer lives.
Speaker 1: Well, let's talk about that because all of this stuff
Speaker 1: kind of leads to that question, if we regenerate so often,
Speaker 1: why do we die? And we'll address that right after this.
Speaker 1: All right, So, Chuck, there's this kind of there's this
Speaker 1: idea that if we are regenerating ourselves every seven to
Speaker 1: ten years, we're like the vast majority of our body
Speaker 1: cells regenerate, why do we age and why do we die?
Speaker 1: It doesn't it doesn't really make sense in that respect.
Speaker 3: Yeah, it's what they think is it has to do
Speaker 3: with your DNA actually in the cell. Our cells as
Speaker 3: we age, even the new ones that get replaced, which
Speaker 3: really stinks, Yeah, become what they call cinicent, which means
Speaker 3: that they can't divide any longer. We've talked about the
Speaker 3: Hayflick limit before, or replicative centizence is basically how many
Speaker 3: times your cells can divide over its lifetime. Yeah, and
Speaker 3: I think like a fibroblast, which is the cells of
Speaker 3: the connective tissue in mammals, it's about fifty cell divisions. Yeah,
Speaker 3: and then it hits that point of centicence and it
Speaker 3: starts sending out repair signals to your body that aren't necessary,
Speaker 3: and that causes inflammation.
Speaker 2: And we've talked about inflammation kind of being the.
Speaker 3: Source of most most of the original problems that will
Speaker 3: eventually lead to your death.
Speaker 2: Yeah, you know.
Speaker 3: Yeah, something becomes inflamed and leads to all kinds of problems.
Speaker 3: There's no repair needed, so it's a false signal. So
Speaker 3: they're trying to come up with drugs. Now, there's one
Speaker 3: called wrap a micene that tries to stop the cells
Speaker 3: from sending out those false signals, which is amazing.
Speaker 1: Yeah, that would be wonderful.
Speaker 2: You know.
Speaker 1: There's another explanation for it as well as that when
Speaker 1: our cells divide, especially over time as we age, they're
Speaker 1: basically making photocopies of themselves. Yeah, and you ultimately, years
Speaker 1: down the road, end up making photocopies of photocopies, right,
Speaker 1: and those don't tend to pan out very well. So
Speaker 1: as far as analogies go, that one kind of makes
Speaker 1: sense that, yes, we have brand new cells, but the
Speaker 1: DNA copies, the DNA blueprints that they're based on it
Speaker 1: have seen better days. Yeah, many years back, you know.
Speaker 2: Yeah, that makes sense. That's a good way to say it.
Speaker 2: We also talked a little bit about whether or not
Speaker 2: the heart muscle itself.
Speaker 3: Replenishes itself in the cells, and for a long time
Speaker 3: they had no idea. But now thanks to our buddy
Speaker 3: doctor Frisson, his pretty much. I don't even think we
Speaker 3: said what his who he works with?
Speaker 2: Did we?
Speaker 1: No?
Speaker 2: He works with the with a K. Karolinska team.
Speaker 3: Oh yeah, just like incredible scientists that are making like
Speaker 3: amazing advancements and trying to figure the stuff out. But
Speaker 3: they did, in fact find that the heart does replace
Speaker 3: itself the muscle cells. About one percent of the heart
Speaker 3: muscles were replaced every year at age twenty five, and
Speaker 3: that falls over your lifetime to less than half a
Speaker 3: percent per year by the age seventy five.
Speaker 1: I spoke too soon. That does make sense.
Speaker 3: Yeah, So what they basically said is about half of
Speaker 3: your heart's muscle.
Speaker 2: Cells will be exchanged during a normal lifetime.
Speaker 1: Okay, which is okay, it is, but as it's slowing
Speaker 1: down over time, I mean the heart's kind of essential.
Speaker 3: Yeah, but they're hoping again to develop drugs that can
Speaker 3: accelerate that process too. Yeah, And I don't know how
Speaker 3: far along they are on that.
Speaker 2: But that'd be amazing.
Speaker 1: So there's this whole thing that kind of came up
Speaker 1: to me man like that I don't all of this
Speaker 1: raises this question to me, right, Yeah, if you look
Speaker 1: at like you or me or any living things as
Speaker 1: an investment, like a molecular investment in the ability to reproduce, right, Okay,
Speaker 1: once you finish your reproductive age, then it does make
Speaker 1: sense that you would just kind of there would be
Speaker 1: built in this mechanism of aging and then death and
Speaker 1: then decay, which is what we do. Yeah, we return
Speaker 1: back to the earth. To put it in kind of
Speaker 1: biblical terms, there's like that whole ashes to ashes, dust
Speaker 1: to dust thing. Sure, it is very very true. And
Speaker 1: if you look at us, and you look at all
Speaker 1: living things as something that exchanges molecules with the external environment,
Speaker 1: takes them in, puts them out right, and you look
Speaker 1: at us as all connected in that sense, like we're
Speaker 1: just like a plant exactly, or we're just like a rock,
Speaker 1: like we're all that stuff, and those things are us
Speaker 1: because we're able to exchange basic ingredients. Then it makes
Speaker 1: total sense that a person would come together, be conceived,
Speaker 1: start dividing as cells, you know, make more of itself,
Speaker 1: and then start to age and then die and decay,
Speaker 1: and then it would give something else a chance to
Speaker 1: come up from that again. Right, sure, but then it
Speaker 1: makes you it makes you wonder, what's the point of that?
Speaker 2: What do you mean?
Speaker 1: Like, think about it. If we're just the same as plants, Like.
Speaker 2: Why are we all here? Yeah?
Speaker 1: Like, if we're if the whole point is to just
Speaker 1: basically recycle materials, because we are just recycling stuff from
Speaker 1: the environment, and we're recycled as we die and decay,
Speaker 1: what is the point? Is our point just to be
Speaker 1: part of the carbon cycle, So we're moving carbon in
Speaker 1: and out of ourselves, in and out of the environment,
Speaker 1: moving it around. Or I don't understand what the point
Speaker 1: is of life? I guess is what I'm saying here
Speaker 1: in nihilis No, I'm not saying I don't believe that
Speaker 1: there isn't a point. I'm just curious what it is,
Speaker 1: because it because if we are the same as any
Speaker 1: other living thing, and the definition of living is an
Speaker 1: exchange with an active exchange with the surrounding environment. They're
Speaker 1: breathing through, eating whatever. Yes. Then and then if you
Speaker 1: kind of take that a little further and say, well,
Speaker 1: clearly we're meant to like reproduce or something like that,
Speaker 1: and then after that we age and die, what's the point?
Speaker 1: Like why not just have one species of living thing? Yeah,
Speaker 1: and just let that do all of your carbon recycling
Speaker 1: or whatever.
Speaker 2: Yeah, I think are you about to quit the show?
Speaker 1: Yeah?
Speaker 2: I see what you mean.
Speaker 3: Like, if we look at ourselves as a purely mechanical
Speaker 3: serving a purely mechanical function right on the planet.
Speaker 1: Like we are to the carbon cycle, what say, evaporation
Speaker 1: is to the rain cycle, Like we're a means of
Speaker 1: moving something along.
Speaker 3: Well, I think that's when you, man, this is getting philosophical.
Speaker 3: I think that's when you start getting into questions of
Speaker 3: the soul.
Speaker 1: Well, yeah, I mean it kind of makes you wonder like, well,
Speaker 1: why would there be more than one species? It will
Speaker 1: be much more efficient to just have one, maybe two.
Speaker 1: There's all these different ones, so why.
Speaker 2: Yeah.
Speaker 1: The fact that that why is just sitting there and
Speaker 1: flashing neon lights definitely made me wonder basically the opposite.
Speaker 1: It's made me think in a different direction and then nihilistically.
Speaker 3: Like, we're only here for so long, and so if
Speaker 3: there is the point is to like make the most
Speaker 3: of your time.
Speaker 1: Well, I think that's a separate that's a separate part
Speaker 1: of it. Yeah, because no matter what conclusion you come to,
Speaker 1: whether Nope, we're just a means of recycling carbon and
Speaker 1: that is it. Yeah, kind of like a Gaia theory
Speaker 1: view of things. Or if you say no, like the
Speaker 1: fact that we're inefficient and redundant as far as that
Speaker 1: carbon recycling thing goes, suggests that maybe there is a
Speaker 1: higher purpose to us. Either way, I feel like you
Speaker 1: come to the conclusion or you should come to the
Speaker 1: conclusion that the one thing we do know is that
Speaker 1: we are here right now, and the best thing we
Speaker 1: can do is make the absolute best of it for
Speaker 1: ourselves and for other people as well.
Speaker 3: Yeah, and there are probably others out there that think
Speaker 3: the whole point is to make as much cash as
Speaker 3: you can, sure you can buy products.
Speaker 2: Yeah, Edward Burnez would.
Speaker 3: Probably say that, Yes he would, and he lived that
Speaker 3: way in Man, that's interesting. I think we should I'd
Speaker 3: love to tackle something philosophical and deep.
Speaker 1: Like the soul meaning of life.
Speaker 2: Yeah, that'd be tough.
Speaker 3: I mean that'd be cool, though, it would be cool.
Speaker 3: We don't delve into that very much.
Speaker 1: No, we should. I'd like to do that. And consciousness
Speaker 1: that's a really interesting one too, Like it doesn't make
Speaker 1: any sense.
Speaker 3: It's a very trippy way forward for this show. Yeah,
Speaker 3: we're gonna start getting weird.
Speaker 1: I took a lot of acid this morning. So, oh
Speaker 1: that's great if you want to know more about some
Speaker 1: just weird trippy stuff. How stuff works has a surprising
Speaker 1: amount of it on there. I don't know. Just try
Speaker 1: typing the word trippy into the search bar. You can
Speaker 1: also type does your body really replace itself? Every seven years?
Speaker 1: And it'll bring up this cool article. And I think
Speaker 1: I said search bar at some point in time. So
Speaker 1: how about some listener mail?
Speaker 2: I like how you specified you took a lot of.
Speaker 1: Acid just a little yeah, a lot fun of it?
Speaker 3: All right, I'm gonna call this multiple We got like
Speaker 3: a bunch of emails in one day about people picking
Speaker 3: at our grammar and things. Oh yeah, so I'm just
Speaker 3: decided to read three of them because they're short. Hey, guys,
Speaker 3: I generally enjoy the episodes, but you do have one
Speaker 3: issue with your grammar and noun verb agreement. You tend
Speaker 3: to say there are many lines of evidence or there's
Speaker 3: lots of experiment showing instead of there are not there
Speaker 3: is when the pronoun refers to a little subject. Check
Speaker 3: yourselves next time.
Speaker 2: Guys. You typically make the mistake about ten times every show.
Speaker 1: Why don't you go recycle some carbon power?
Speaker 2: That's from Kim Keller in Temple Tariffs, Florida.
Speaker 1: Thanks.
Speaker 3: I always like to pick apart their emails too, about
Speaker 3: because people usually make a mistake or two in their
Speaker 3: own emails.
Speaker 2: Hey, guys, this one's from Blair. I love the show.
Speaker 2: I hate to be nitpicky.
Speaker 1: They always say that, don't yeah right.
Speaker 3: Before they nitpick, But I have a grammar direction. It's
Speaker 3: been bugging me for months, and Stonehinge was a major offender.
Speaker 3: At least one of you not naming names frequently used
Speaker 3: the word further when you really mean farther. The latter
Speaker 3: term is used for literal distances. Further is only supposed
Speaker 3: to be used figuratively.
Speaker 1: Huh.
Speaker 2: I didn't know that, Okay, so thanks Blair.
Speaker 3: Yeah, and then the last one, Phil who was an
Speaker 3: English and grammar pronunciation freak. He says, hey, guys, when
Speaker 3: there's an Italian word, you take your time to pronounce
Speaker 3: it properly. The same with Japanese in the Far East
Speaker 3: in general. So why don't you extend that same courtesy
Speaker 3: to English.
Speaker 1: Words because we're masters of the language.
Speaker 3: And I mean words actually in the UK vernacular, not
Speaker 3: American English. Salisbury, No, it's Salisbury, the Marlborough Downs, Nope,
Speaker 3: marl bro Downs.
Speaker 1: Well, we're using the American vernacular because we're in America
Speaker 1: and recording as American.
Speaker 2: That's from Phil.
Speaker 1: I had I addressed all those I think.
Speaker 2: Yeah, I think so. I feel good about it.
Speaker 1: I think it's good and very big of you two
Speaker 1: have read those as listener mail. Why not nice job.
Speaker 3: Man, Yeah, we just we don't profess to talk gooder
Speaker 3: than other people. We just do our little thing here
Speaker 3: in the studio, send it out into the world nice
Speaker 3: for people to pick apart.
Speaker 1: What we're doing is we're creating grammatical tableaus like that
Speaker 1: Highlights magazine where it's like pick out the things that
Speaker 1: don't belong. Yeah, that's what we're doing for you, guys.
Speaker 3: Yeah, keep you entertaining if you didn't have something to
Speaker 3: complain about it, it'd be so boring.
Speaker 1: Yeah, if you want to nitpick or compliment or suggest
Speaker 1: something whatever. If you want to get in touch with
Speaker 1: us for any reason, you can do that by tweeting
Speaker 1: to sysk Podcasts. You can join us on Facebook dot com,
Speaker 1: slash Stuff you Should Know. You can send us an
Speaker 1: email to stuff podcast at house stuffworks dot com, and
Speaker 1: as always, joined us at our homeown the web, stuff
Speaker 1: youshould Know dot com. Stuff you Should Know is a
Speaker 1: production of iHeartRadio.
Speaker 3: For more podcasts my heart Radio, visit the iHeartRadio app,
Speaker 3: Apple Podcasts, or wherever you listen to your favorite shows,