Daniel and Kelly’s Extraordinary UniverseDaniel and Kelly talk about the science behind aging trees, and why some trees live so long.
The oldest tree we know of is Methuselah, a great basin bristle cone pine that is almost five thousand years old. Methuselah began putting down its roots during the Age of the Pyramids in ancient Egypt. It also lived through the rise and the fall of ancient Greece and ancient Rome as well. Pamarabi, Nephertidi, Buddha, Pythagoras, Confucius, Socrates, Alexander the Great, Cleopatra, Genghis Khan, Joan of Arc, Da Vinci, Copernicus, Ivan the Terrible, Shakespeare, Pocahontas, Newton, Hamilton, Mozart, Napoleon, Lincoln, Darwin, Nightingale, Pasture, Edison, Gandhi, Hitler, Parks, Mandela Martin, Luther King Junior, and Betty White. Generations of humans have struggled and strove, some making the world better, some making it worse, but all of them lived out their entire lives in just a sliver of the time during which Methuselah has been patiently growing in the White Mountains of California. There's something both bewildering and awe inspiring about incredibly old trees, and today we're going to be talking about what we know about them, how do we age trees, and how and why do some trees live so long? Welcome to Daniel and Kelly's extraordinarily tremendous universe.
Hi. I'm Daniel. I'm a particle physicist, and I round myself up to fifty years old.
Hello. I am Kelly Wiener Smith. I study parasites and space, and I round myself down to forty. You're even older than I am than I had realized. Daniel.
Oh wow, what a wonderful thing to hear.
All about how you round. Although you know, I thought we had both agreed that we round up on average, But at only forty two, I think I'm gonna go ahead and round down.
Yeah. No, I think that's fair. Who really needs more significant digits than one? Right?
That's right? That's right. Do you have a favorite tree?
Do I have a favorite tree? I love the redwoods, you know, out here in California. I gotta say that's something spectacular about California and the mystery, the majesty of being the presence of these super tall and super old beings and thinking about all the things they've seen experienced. I love it. I just love old trees in general. Like when you drive down a street in a neighborhood that's like one hundred years old, and the trees like cross over the street or have all these wiggles and branches where it's like a new suburb with these like tiny little potted plant trees, it's just a little sad. So old trees are wonderful because it's something you got to earn. It just takes time. You know, you can't like fast grow a tree to a huge size.
I totally agree. When I lived in California, I had to go see the Redwoods and I realized that I'd been like looking up at one of those trees with my mouth open, and I was like so glad nothing had fallen into it, because I was just like I must have stood there for, you know, fifteen minutes just looking at the same tree being like, Ah, the things that you've seen or you know, have been alive through. It's just incredible. And then I had the great pleasure of working at Race University for a while, which I know is where you did your undergrad and they've got that running track around the outside of the university that is surrounded by live oaks, and they're the ones that have those like tortuous arms that like go back, they down, they touch the ground, they come back up again. Oh, they're so gorgeous. I actually don't know how old those live oaks are, but there's something about a big tree that I love.
Yeah, and Rice has so many trees. I think there's something in the charter that they have to have more trees on campus than students, that they really preserve the trees on the campus.
I can't believe they've got more trees on campus than students. If so, they got to shut that place down. Man, I don't think that's working out.
Well. I gotta ask you call of the obvious question. Given California's redwoods and the majesty of our old trees, what does Virginia have to compare. I'm giving you an opportunity here.
Oh my god, this is easy. So California is beautiful. But have you been to Shanandoah National Park?
Oh? I have land of many uses.
Many uses? What do you mean, like you're gonna cut my trees down?
No? I just remember camping in the Blue Ridge Mountains one time, and there was a sign when you enter, It's like welcome to the Blue Ridge Mountains a land of many uses, and well, I wonder what that means.
Yeah, I don't remember seeing that on the side, but like you've gone camping and the Blue Ridge answer is obvious. It's just so gorgeous seeing all of those rolling hills with all the trees and the like mist coming up over them in the mornings and seeing the sunset. There's like no more beautiful view in all of the United States than what you get. I'm laying down the gauntlet, man.
I was with you up until that point. I mean, I like the Blue Ridge Mountains for mountains, they're cute. I mean, they're not that tall or that.
Point d That's why they're so nice to walk.
I like a nice granite topped mountain, you know, like above the tree line. That's my jam. And the Sierras, for example, Oh yeah. And I just don't think you can compare to the majesty of the coastal Redwoods. You know, nothing stands up to that. In my opinion, those are beautiful.
I'll give you that. I don't feel like I want to pit one natural beauty against another, but I can say that in grad school I tried hiking White Mountain where the Bristol Cone Pines are. So we talked about Methusela in the opening, and you know, I was climbing up there and the air was getting thin and I was like feeling miserable, and you know, so no, give me Shanandoah any day where I could breathe. It's like I don't want to go to space. I don't want to go to White Mountain.
Yeah. No, it's beautiful, absolutely, I'll give you that. And you're right, we shouldn't pit one against the other. There's lots of different ways to be beautiful and we should appreciate all of it.
Amen. All right, And so we had this absolutely incredible question from a listener's son about old trees, and that's what we're going to be talking about today. But before we listen to the question, I want to remind you that you can send us your questions or you can send us your kids questions at questions at Daniel and Kelly dot org.
We really love hearing from you, and we love hearing from your kids. Thank you to everybody who listens to the pod with your kid. It's a great way to start conversations about science.
Yay, all right, So let's hear the question that we're chatting about today.
Hi, Daniel Kelly, I have a question, why does some trees live longer than other trees? And why do they live longer than people?
This is a great question because this is a question I've had since I was a kid, looking at those redwoods and wondering like, why do they live so long? How do they live so long? What's going on?
Yeah, it's a fantastic question, and it was one where when I listened to it, I thought, oh, this is another one where I don't really know the answer, and so I was thrilled to have an opportunity to do some research. And so let's start this conversation by talking about how we even go about are in the first place. I think a lot of us are familiar with the idea that you can age trees based on their rings, but it's a little bit more complicated, So.
You can't just chop down the tree and count the rings.
Danduel, Yes, but then you're a monster.
Well it reminds me of that Far Side cartoon where the guy is standing there with his son and axe and he's chopped down some big tree and he's going through the history of the tree, all the things. The tree has survived until of course that day that he chopped it.
Down, right, but it couldn't survive us. Uh, that's sad.
So tell me then, how do we know how old a tree is without chopping it down and counting its rings.
Well, for a while there, we were using relational ages, so you would say, oh, well, the tree was planted around the time the Parthenon was built or something like that. And so Pliny was using these relational ages where he would age trees based on historical stuff that was happening at the same time.
But how would you know what historical stuff was happening at the same time. How would you know this tree was planted at the same time the Parthenon or something.
I think records and institutional memory. But you're right, I mean, you don't know unless somebody happens to know local knowledge.
And that you can trust that knowledge.
Yeah, I bet they got a lot of ages wrong. But that can't work great, I.
Mean, I'm sure there's a lot of mythology, right. People are like, there's trees thousands of years old, and because people are bad at deep time, you know, oh.
My gosh, so bad. And I was reading this book called Elder Flora, and it talks about sort of the history of our relationship with old trees and how we often get the ages wrong, and how trees become important for religious ceremonies and stuff, and so anyway, anyone who's interested in old trees, that's a good book worth checking out. But towards the end of the nineteenth century, and I'm surprised this wasn't common earlier, we started getting a handle on aging trees by counting their rings. So let's talk about the science behind where these rings come from.
Yeah, why do trees have rings? And why do they have one ring per year? Anyway?
Yeah, right, great question. Why doesn't the inside of a tree all look the same?
Yeah, I mean I don't have rings. If you cut me open, you couldn't count my age.
Well, we don't really know until we try.
Maybe we should start with a core sample.
That's right, Yes, that's right. I'll get off my increment borer. But we'll get to that. So, so here's how trees grow. All right, Say you do do the horrible act of cutting down a tree, which of course sometimes you have to do, and we all use paper so anyway, no judgment. So you cut down a tree, you're looking at the center of a tree. The center part of the tree is called heartwood. And if it's a big tree, that center part is actually dead.
Why is it called heartwood if it's dead.
Trees are weird, and that's going to be the theme of today's show, I think, is that trees are weird. So, you know, the listener wanted to know why humans don't live as long as trees, and I think the answer is trees are weird. And you know, I'll do a better job of answering that at the end of the episode. But that's the take home point. So the center is dead, and it's dead because it no longer has access to water and nutrients that are come up through the xylum, which will get you. So the next level you've got is the sapwood, and the sapwood is the level where you still get water that's coming up through the xylum. So you've got essentially I think of it as like a series of tubes, but it's really like specialized cells that go from the roots up through the trunk of the tree and into the canopy. And so the sapwood is getting access to that water and to the nutrients. Next to the sapwood is the cambrium, and the cambrium maybe the cambrium we all know how good I am at pronouncing things is going to be very important for the rest of this episode. So this is the layer where you have the growth happening. So on one side, towards the outside of the tree, the cambrium starts producing bark, and that bark is going to build up over time, and that's going to protect the tree. Towards the inside of the tree, it's producing the sapwood, so it's producing more of that like woody tissue that you would build a house out of, for example.
Woody tissue otherwise known as wood. Yeah, well for us folk.
But wouldn't bark be woody tissue? Kind of Also, I don't know, I see, but you wouldn't necessarily build the house out of bark. So I was trying to be a little more specific.
But yeah, well, I don't want to blow my nose on a woody tissue, So I guess it has lots of meanings.
That's right, that's right.
Well, before you dig deeper, my first question is, like, are these hard divisions is there like an edge between the heartwood and the sapwood, or is it like a spectrum where like in the middle it's something that's sort of hearty sappy, or is it really like a hard bright line there.
Yeah, that's a great question. So I'm thinking back at the tree cookies as they're called, that I've looked at. So this is like you slice through a tree at two different parts, and it's sort of shaped in a circle, kind of like a cookie. And I feel like often it looks like there's a pretty clear delineation between what would be the heartwood and what would be the sapwood. The heartwood's like a different color, but it probably does have like layers that are gradations in the process of dying, essentially interesting versus cells that are still being fed, would be my guess, right.
And so the Cambrian is the thing that's making more soapwood on the inside and more bark on the outside. Is that the only part of the tree that's growing. The tree is not like expanding uniformly, sort of like the way the universe expands. It's like only making new rings around the outside.
Yeah, it's only making new rings around the outside. And so say you were to like put a nail into the side of a tree, and you came back fifty years later, that nail would still be at the same height that you had put in, but it would be essentially getting like absorbed by the tree, like layers would have grown around it, and so either that nail wouldn't be visible anymore unless you actually cut into the tree. And as someone who lives out in the woods in an area where there used to be a lot of barbed wire fencing, it's amazing how often we'll cut into a tree and the chainsaw blade will get messed up because it turned out there was a barbed wire like in the middle of the tree and the tree had just grown around it. It was like, nice, try humans, I grow around you.
And so if I had like two models of growth in my head, one where like every part of the tree is expanding, so heartwood is always heartwood just becomes bigger. Sounds like you're suggesting a different model where like sapwood becomes heartwood. Is that what's happening here?
Yeah, So sapwood and heartwood are both made out of xylum cells, which are the cells where you get water and the stuff that's dissolved in the water that goes from the ground through the roots and up towards the top of the tree. Both sapwood and heartwood are dead. Those xylum cells are dead, and as those xylum cells get more and more compressed, they become heartwood. So the difference between sapwood and heartwood is that the xylum cells have been compressed so much that water can't move up them anymore, and that happens as you move towards the center of the tree. So sapwood becomes heartwood over time.
And then that heartwood basically never changes right because it's dead and now it's just structural.
So in most trees, that heartwood stays structural and it stays there. And so when you bore through the center of a tree, you can pull out a plug where you can see all of the lines throughout the entire life of the tree. But there are some kinds of trees, like the Boa bab in Africa, where the inside is sort of not the same consistency of wood that most of us think of, and it tends to sort of decay and rode away, and so you can't use increment bars for a lot of those trees because the inside is no longer there.
But for most trees, basically the living part of it is like a hollow cylinder's more like a tube than like a filled in cylinder. And that's expanding and leaving behind its corpses.
Yeah, isn't that crazy?
That is crazy, totally nuts. It's like the opposite of a snake. A snake like sheds its skin, but the living part is on the inside. This is like if the skin was the living part.
Yeah.
Wow, trees are weird.
Yes, trees are so weird. Okay, but so why does that growth leave behind rings instead of just like a homogeneous center.
Or why is it linked to the year instead of something else?
Right?
What's going on every year that makes this mark inside the tree?
Right? So you get rings in areas where there's clear seasonal differences, and that could be winter summer, but it could also be wet season and dry season. So not all trees have rings, and in particular, these rings are either like much fainter or maybe even impossible to see. And areas where conditions are more homogeneous or more similar all year long, like a born place like California probably, But anyways.
If by boring you mean consistently wonderful, then yes, all.
Right, fine, Okay. So at the beginning of a season, the wood is a little bit lighter, and it is more aimed at being able to transport nutrients and water up and down during the massive growth that starts at the beginning of the spring. And so that kind of wood is called early wood, because apparently these folks are just as clever at naming things as the people who named the rings of Jupiter. If was that Jupiter or Saturn where the rings are abc.
That's definitely Saturn, probably a Jupiter, though I haven't looked that up.
Okay. And then after the earlywood, you get do you want to go ahead and guess.
Daniel, I'm gonna guess latewood.
Yeah, yep, you get lightwood. And lightwood I think is more about structure, and so it tends to be tighter and closer together.
I see. So the kind of new wood that's grown depends on the conditions on the ground, and that changes through the year, and that changes the kind of wood that it's grown.
Yep. So every year you get this pattern of like light than dark, and those are the rings that you see.
And I think, say again, why the latewood is darker than the early wood.
My understanding is that the late wood is meant to be more about structure, so it doesn't need to be so loose, so that water can go up to feed the many leaves that are growing at the beginning of the season. When you're at the point where you've got all your leaves, or maybe even the leaves are starting to come down, the new growth is mostly just about structure, and so it's a different kind of cell that looks a little bit different.
Yeah, you make it sound like it's intentional, like the tree got together and it's like, all right, I think we're ready for some structure. In reality, of course, is just sort of what has worked right and we're reverse engineering it.
Yeah. It also is responding to the environment and so on very wet years or years with really good growth conditions, the distance between rings is much bigger because the Cambrian was able to put in more rows of cells, and so you get a greater distance, whereas in years where there's droughts or conditions are bad for some other reasons, the distance between the rings are much smaller.
And do you always get a ring, Like what about the year without a summer, or when there's like a volcanic eruption and we just don't see the sun. Can you trick trees into thinking a year hasn't passed?
So I don't know the answer to that. I have aged fish based on their scales, so I have some knowledge of how the environment impacts aging dynamics, and there are definitely some years where it's very hard to tell the difference between the rings, or to tell if there is a ring in this particular place or not. I'm guessing the same thing happens with trees. I would also guess that when you age a tree and you say it's four thousand, five hundred and eighty seven years, you really mean like four five hundred and eighty seven plus or minus thirty or something like that. Oh sure, yeah, But you can use this tool called an increment borer to go through the center of a tree and pull out a tiny little pencil shaped chunk where you can go through, and you can age it by counting the rings. But you don't need to kill the tree. It can just handle this little bit of damage. It's like drawing blood from a human or something. And if you get enough of these, you can actually look at climate patterns in a region over time, and so trees give us a little bit of window into the past. One tree doesn't really do it, because it could be like one year it was underneath a bigger tree and so it got shaded out so it didn't grow as much. And then if that tree dies, you know, the next year its growth is bigger. And so there's some other stuff to pay attention to as well. But we could look at climactic patterns by using these tree rings.
Yeah, I remember reading that they use old trees for things like understanding the atmospheric carbon content and all sorts of stuff. It's like an incredible record of what's happened on Earth because it's so sensitive. It's so lucky that it works this way. I mean, I can imagine lots of other ways trees could have evolved that they didn't respond in this cyclical way.
I know. And also for managing fish populations. It's amazing that scales tell you how old they are. We really lucked out that nature works in this way.
Nature is a good record keeper, right, They're hints all over the world about what happened on this planet. We just have to be good detectives and like figure out how to read them. And one thing I love about science is all this work that people have done, you know, this like Yeoman work to figure out, like how we can use some part of nature to reveal secrets of the universe. Right, you don't just sit around and like let the universe download it into your brain. You've got to go out there and do the work and figure out like, oh, we can use this weird rock and oh, terms out trees do this weird thing, or fish do this weird thing. Like there's so much of experimental science that's people's realizing they could take advantage of a quirk of nature.
Yeah, and then there's so many things you can do with it. It's like one of the favorite things that came across was that archaeologists are using tree rings to try to date structures. So if you find, for example, a beam in an old house and you assume that it was cut down to build the house, then you can look at other tree cores in the area and sort of match up the fast growth years with the slow growth years, and then you can back date to figure out when that structure was built, even if you don't have that record anywhere. It's so amazing. The more you understand about the world, you get all of these surprising linkages that you can use to learn even more. It's super cool. It's incredible, Okay, But to get back to carbon fourteen dating, it turns out that carbon fourteen dating is also a method that we use to date some of the trees that we come across. So we already talked about the baobab, which sometimes rots in the inside, and so you can't use an inc bor to like get a little sample of the tree to age it because it doesn't really have a center. But you can use carbon fourteen dating and pull the innermost wood that you can find to get an estimate for how old the tree is. So these are the various methods that we use to age trees.
So, like some of the interior records essentially have been destroyed, but you still have a few and so you can say the tree is at least eleven hundred years old or at least seventy five years old or whatever, but you don't know what you're missing.
Yep, that's exactly right.
Yeah, fascinating. Well, it's incredible to me how long these trees live. And you know, trees to me are just stunning creatures, you know, Like if we didn't have trees, or if I'd never seen a tree and you describe them to me, like, hey, there are these things that build themselves out of air over time, drinking sunlight and reproduce themselves and provide oxygen. I'd be like, that's some crazy science fiction nonsense. But they're real.
It's amazing, and they're beautiful and we can use them to build our homes.
All right, Well, I want to hear all about the world herd holders for oldest trees in the world, but first we have to take a quick break. Okay, we're back and we're talking about the weird, the amazing, the beautiful, the fantastical, the California and the Virginian, the worldwide tree. It's everywhere, and it provides us with oxygen and teaches us about the history of our own planet. So Kelly, tell us, where are the oldest trees in the world and are they in California?
Maybe they're in California. There are a couple other contenders for oldest tree in the world, but at the moment, I think the most widely accepted oldest tree in the world is Methuselah, which we talked about in the intro, somewhere between forty five hundred and five thousand years old. The coordinate are not public because they don't want people to go and like carve their names into the side of it, because humans do stuff like that. Guys, do we just.
Hold on for a moment, like back up, Like, wow, five thousand years old? What was happening on Earth five thousand years ago? So this tree is like older than the Great Pyramids.
This tree put down its roots during the age of the Pyramids. I think this is the Old Kingdom.
Wow.
Yeah, incredible. So it saw the fall of ancient Egypt, the rise and fall of ancient Rome, and ancient Greece. Like we said in the intro, so many generations of humans. It's wind boggling. I'm not very eloquent. I can't capture this adequately. It's just incredible.
It really just gives you a sense for the tiny blip of time that we exist on this planet. And of course even that by five thousand years is a tiny blip of time for the planet. That's the thing that these old trees do for me. They give me this like tiniest taste of the deepness of time, the incredible vastness of time in the universe more broadly, and then of course on Earth. So do you think that these trees are going to see, you know, the fall of our current civilization? How long new bristle cone pines live? So?
I think the bristle cone pines that are five thousand years old are not looking young. But I do think that there are some clonal organisms that we'll talk about later, like those stands of quaking aspens that can live for over ten thousand years. And I hope that we live longer than the quaking aspen stands that are alive today. We as a species, not me personally, but I don't know. We'll have to wait and see. What do you think? Are we an imminent declined Daniel?
All that remains to be seen. I was mostly asking about the lifetime of these trees. Oh, if you find a population of trees and the oldest ones are about five thousand years old, that means either they evolved five thousand years ago and they're going to live a long long time, or that's roughly as long as they can. Like have bristle cone pines been living for five thousand issh years for millions of years, And this is just sort of like how long they typically live and we're visiting the old folks Home for bristle cone pine.
I don't know, and I don't think that most people know. What would you have to know in order to answer that question? I guess you would have to find dead bristle cone pines. You could age when they died and determined that they had been alive for five thousand years. I suppose in these dry environments that kind of petrified would could exist, but I don't know if it does exist.
Yeah, well, we can tell when the tree dies, right because of carbon fourteen dating, and you could count its rings, So in principle it should be possible to know.
You could count its rings if it didn't. Like so, most of the trees on my property eventually they rode away and decay. You can't find them anymore. But if it petrified and you could find it, I don't know the answer, But my guess would be that they have been living for a very long time. But if you go out to a long enough time period, you have to start thinking about things like, well, where were they when the last glacial event happened.
Oh yeah, And it.
Turns out that bristle cone pines tended to be up in the mountains, high enough and out of the way enough that they weren't bothered by the last glacial event. But it could be that there are trees out there that would live for a very long time, but they happened to be in habitats where when the last glacier came through, it knocked them all out because they can't run away like we can. That's one of the downsides of being a tree.
Right, That's amazing. These guys live so long. You have to think about the changing conditions of the earth when they were babies or when they were growing up. That's incredible, it is, all right, So Methuselah is maybe a contender for one of the oldest trees on Earth. What else do we find in the old folks home for trees.
Well, so there was a tree called Prometheus that was also a bristle cone pine. But usually the contenders have to be trees that are still alive. But unfortunately Prometheus was cut down in its five thousand year prime.
Oh no, was it by some terrible tourist.
No, it was by I think a grad student, so I know, okay, So there was this misconception that old trees were probably the biggest trees, and that makes sense, you know, you look at the redwoods and you're like, oh, you might be so old. But actually there's this trend where the older trees within a species tend to be the smaller ones that started their lives growing more slowly and maybe even over time didn't get to be as big. They're just sort of like tiny and stodgy, and I love it. And so I think this student didn't realize that they were dealing with what might be the oldest tree on the planet, and so they were trying to get the age. The exact details of the story have been sort of lost to history, but a version of the story is that the student was trying to get the age using an increment bor, so this thing where you hand crank it into the tree, and that just wasn't working out, and so they actually did get permission from the park Service to cut the tree down. Oh no, and then when they cut the tree down, it just turned out that it was five thousand years old. Oh my god, maybe the oldest tree ever.
That must have been heartbreaking.
Yeah. I think that student did report later that they regretted for the rest of their life that they cut that tree down.
Imagine surviving for five thousand years. And then some grad students like, oh.
Man, yeah, the glaciers didn't get you, but the grad student did.
Academia comes for us all eventually.
Oh man, yep, it gets us. So anyway, tragic story. So there's also a tree in Chile, the Alersie Tree, and again sorry my apologies of mispronouncing it, but there is a tree in Alerseay Castero National Park that is eighty percent likely to be over five thousand years old. It's estimated to be five four hundred and eighty four years old, and so that tree could win.
Where do you think that eighty percent uncertainty comes from? Is that from like the rings being fuzzy or what we were talking about earlier, like not every ring is present or visible.
The rings being fuzzy, I think is a problem. Another problem is that sometimes where you go through the tree can influence how many rings you see, and so people tend to do the boring, like you know, to get your sample at about like chest height. But I think if you go down even lower. Sometimes you can get some additional rings. It's just complicated. No answer is ever as clear as you want it to be.
In science, well, I appreciate that there's uncertainties, you know. I've seen talks in biology where you see like data plotted with no uncertainties and like a line drawn through in it, and you're like, what are we doing here, folks? So I'm always very impressed when I see biology with air.
Bars so used to you, hey man, A lot of us understand error bars and confidence intervals and would never publish a paper without them.
I'm still glad to hear it.
M all right. Anyway, we had talked about that tree, the African baobab, where the inside sometimes hrats out, but with carbon fourteen dating and then attemp at aging the trees using the rings for the trees where that works, we think that they can live to be as old as two thousand, five hundred years.
Wow.
There's about twenty five species of trees that we know of that we think can live to be a thousand years old or older. But it's important to note that not all trees live to be super old. Like right now, it's spring in Virginia, so it's more beautiful here than anywhere else. And the dogwoods are going to be blooming pretty soon. And dogwoods live to be like twenty or thirty years. They can live to be as much as like eighty years, I think, but like a lot of them only live to be twenty or thirty years, So it's not the case that all trees do outlive humans.
Well what about the famous redwoods. These are old trees also, but they're not in like the top ten oldest trees. But there must be hundreds of years old.
Right, Yeah, so redwoods and giant sequoias are amongst the species of trees that can live to be over a thousand years old, So they're found amongst those twenty five ish species we know of, But I don't know that there are any redwoods that are contenders for the oldest tree.
Hmm, all right, So then why is there such a huge range. Dogwoods live happily for just a couple of decades, bristle cone pines scratch out a thorny existence for thousands of years. Redwoods become enormous over about a millennium. Why do these things live such an incredible range?
So this is ecology m M. So what do you think the.
Answer is, we don't know.
Yeah, we don't know. Yeah, both of those work. So the papers that I read, it seems like, so, you know, there are those twenty five species that I mentioned, Yeah, in many cases they are not closely related tree species, or they're not super closely related, And it seems like we have a different answer for a lot of those different species. So, for example, part of why we think the bristle cone pines have lived so long is that they manage to eke out in existence in an environment that is very dry and is up at the top of a mountain, and it's not a nice environment for other competitors or for pests, and when they escape from these competitors, in these pests, they can just focus on slow growth and they can live for a really long time because they don't have to worry about these other competitors. But then you get the redwoods in these moist environments with lots of competitors and lots of pests, and they do manage to live for a long time. And so it seems like you'd need a whole different explanation to figure out why redwoods are able to live for so long.
It seems to be sort of connected to the question we talked to Katie about, you know, our strategists and case strategists like, from a species point of view, it doesn't really matter if you live a long time. Another totally valid strategies to just like have a kid every thirty years and then die off and make room for your kids, right Like, they're definitely different strategies from an evolutionary point of view that could work to propagate you species down through history.
Right, yeah, exactly. And additionally, our data set is complicated by things like what we've talked about already, which is, you know, during the last period when the glaciers came through, maybe there were a bunch more species that would have lived for five thousand years, but they all got wiped out by the glaciers. Another problem is that humans have been cutting down trees for a really long time to build our houses and you know, to build our skyscrapers, just to build a lot of different stuff, and so we have removed a lot of trees from the landscape, and so what we have left to age is maybe a subset that is less informative than it would have been if all of the trees had still been there, or every once in a while you get an outbreak or something like the United States used to have tons of chestnuts, Like everywhere I look now there's pines and oaks. If I had lived here before, a chestnut, like the most common tree in my area would have been a chestnut. But now we don't have any of them in the area, And so we have a bias subset from which to try to answer these questions why do some trees live longer than others?
But we always have a bias subset, right, We just have a subset that happened to survive, that made it through the deaf gauntlet of the present conditions. We never know, like on average, over a thousand parallel earths, what would have survived. We just got the ones that happen to get lucky and happen to survive this time. Right. Isn't that always true of evolutionary history?
Yes, I'd say it's also sort of always true with physics too, Like, you know, you only have the information that you've already created tools for. You don't know what you're missing, And so I think in general, a big part of being a scientist should involve being humble about what you do and don't know.
No, it's important to always put this in context, right and remember that we have a tiny fraction of the information, and that fraction is biased for sure.
So one thing to note that we talked about earlier is that growing slowly seems to be associated with longer life for trees, and that can either be at the species level or within a species. So it looks like individuals that tend to grow slowly early in life are also the ones that tend to live longer. So if they're growing more slowly, they're investing in a denser, higher quality would and maybe they're also investing in stronger roots or some chemicals that can fight off pests, and so this investment in strength helps them when, for example, a hurricane or tornado comes by. Maybe they're likely to be still standing when that's done. Whereas if an individual grows quickly, then the quality of the wood that they produce is less good and so something is more likely to take them out if something like a hurricane or a tornado comes through. So individuals who grow more slowly tend to be the ones that live longer.
Well, how does this map two long and short lifetimes for other critters, like in mammals with the longest lived mammal.
Yeah, so this idea does map pretty well to the rn K strategy stuff that we were talking about with Katie when she was on the show. You end up with some species that grow fast and some species that grow slow. There's also this idea where if you are not growing as fast as the other mammals and you invest in growing really quickly to try to catch up, the quality of that fast grown muscle or fast grown you know, bones, anything that you grew fast is probably not as good as if you had grown sort of slowly and invested in doing it right. So in multiple flora and fauna, we see the signature of fast growth sometimes coming at the expense of the quality of that growth.
I guess I wasn't that interested in mammals in particular, more like animals, because I know that you know, there's some sharks that have lived for hundreds of years and turtles lived for hundreds of years, whereas like I know, mice live for just a few years, but they're also tiny. So just like size and age correlation work more broadly.
I don't know it would be fun to do a whole episode on aging at some point. I know greenland sharks can live to be like hundreds of years old, but I don't know why we think greenland sharks in particular live that long. Somebody might know, but I don't know.
Somebody's probably gone down and trying to take a core sample of a greenland shark and a bit that didn't go very well.
No, No, they do not look like happy show. They look old. You look at them, and they've got like sadness in their eyes. Not that all old people are said. I'm backing up. I'm backing up.
Old trees don't look sad. Old trees have a grace and a beauty that's very hard to match.
Oh my gosh, they do. That is true for so many ancient individuals.
Yeah, all right, so let's hold some reverence for the old folks among us and take another break so we can gather our energy and talk about how trees live so long and to answer the listeners question about why they live longer than people. Okay, we're back, and we're talking about how California is beautiful and filled with the oldest, the tallest, the biggest, and probably the most beautiful trees in.
The world because there's not a lot of competition, because what trees would want to live there? If they could live in Virginia.
You're saying, if you could survey trees and offer them a spot in Shindoah, they would all pick up and move.
Yeah, I bet who would?
You might be right, You might be right. It is beautiful, all right. So tell us these oldest trees, how is it that they go about living so long? What tricks do they have under their bark that let them survive for thousands upon thousands of years?
So trees are so weird and so unlike anything I've come to expect as a mammal. There are things I expect bodies to do, and trees just don't follow any of those rules. Okay, So one and this is kind of amazing. So we talked about that cambrial layer, the layer that is growing the bark while also growing the wood inside of the tree. The cells in that layer don't show evidence of sinescence.
What sinescence?
So sinessence is like getting old and sorry everybody, but you know the quality of the cell sort of deteriorating over time.
So you're saying, in some trees, you can see these cambria layers aging, but in the trees that live a very long time, they just keep going.
I think that you don't see cambril cells aging in like any trees. Oh, and this is why trees in general on average tend to live a long time.
Oh fascinating.
We're still trying to figure out why this happens. But the cells just seem to have this like fountain of youth thing going on. And so because the cells aren't aging, the things that usually kill trees isn't you know, it just got old and stopped working. But it tends to be things like fire or insects or erosion or hurricanes. It's you know, things external to the tree that end up being the cause of the tree death.
So it sort of seems like the trees constantly replicating itself, like every years you basically have a new tree built around the body of the old tree.
So I'm gonna jump out of place in my outline now, because yes, it has this amazing way of replicating itself. Where for some trees, if it like for example, falls over, or if some of the branches touch moist soil, the branches or the part of the tree that fell over can start putting down roots and a new sapling comes up from there.
What that's crazy. It's like if I put my elbow in a bowl of oatmeal and like turned into.
A person, another Daniel. You know, it wouldn't be like it produced one of your kids. It's like producing a clone of you. Oh so, like another Daniel emerges from your oatmeal. I'm glad I didn't give you oatmeal when you were at our place, So.
Because you can't take more than one of me, that's for sure.
No, that's actually a world full of Daniels would have been great.
But nobody believes you. All right. So these trees having these weird ways of cloning themselves.
Yeah, so they've got these weird ways of cloning themselves, and they also have other weird ways of fixing themselves. Throughout the tree, there are these buds, and some of the buds will like turn into branches and stems and leaves and stuff like that. But some of those buds stay dormant, and while the leaves are growing, a hormonal message is getting sent to those buds that says, stay put, don't develop, stay a bud, And so it stays a bud and doesn't do anything. But then if something happens and like that branch falls off or something, and those leaves are no longer sending the message, that bud snaps into action and starts, you know, building a new stem or something like that. So trees have all of these different parts that are waiting to emerge. So it would be like, if you are fingers, we're sending a message to your wrist saying we've got enough fingers, don't worry about it. But then if you lost your fingers, that message is no longer being sent to your wrist, and your wrist is like time to grow more fingers, and so it's just ready to regenerate what had been lost. And it's just kind of like standing in wait.
Wow, that's incredible. That's so different from the way our bodies work. It feels so alien.
So alien. Yeah, okay, And so another thing that's amazing about these trees is you know, part of them is alive, but a lot of them can be dead. And so for example, some trees, and not all trees, but some trees have this system where essentially the like pipes that provide water to the top part of the tree the xylum. Instead of essentially like servicing all of the tree, the pipes service a very particular part of the tree. What yeah, And so like with bristle cone pines, erosion exposes the roots to like dry air, and it kills some of the roots. But as long as some of those roots are still in good shape, they can provide water and nutrients to like a branch or a couple different branches. And so you can end up with like I don't know, eighty percent of the tree being dead, but twenty percent sliver still having leaves, still being able to produce seed and still being alive. And so it's like a very slow process of death, but it still counts as alive because it can still reproduce and it you know, it's still producing green leaves.
I never thought about that how one root doesn't service the whole tree. It's like this root is for that branch, and this root is for that branch, And so if you kill some of the roots, you killing part of the tree. You're not just weakening the whole tree. That's fascinating. It's like if I had ten mouths and I need to like feed this one for that leg and this one for the other leg, and like, oops, there wasn't any oatmeal left from my right arm, so that's just going to be hungry today, and that's weird.
There are tree species where like one root has you know, like multiple we'll call it pipes that come out of it, and it feeds different parts of the tree. But there are some species of tree where you get this more tight link between a certain set of branches and a certain root, and in that way it's able to sort of die in sections and eke out in existence for longer.
It's almost more like a community than an individual, right. They're just like a budge of brain systems that are sort of like growing together, and some of them die off and some of them continue. It's like a little community of mini trees.
So I think that comparison works better for our next example. I feel like what we just talked about would be more like, you know, everything, but my hand could die, but my hand is still alive, and so you'd still call me alive.
That sounds like a horror movie I don't want to see.
Yeah, no, me as well. But the final example for how trees managed to live so long is cloning. So you have these trees called quaking aspens in the Rocky mountains, and they're absolutely gorgeous. They're like, you know, these long white trees. They turn beautiful colors in the fall, and their roots are able to put out what's called a rammit Ramit is a general word for an individual clone when you have like a clonal organism, but it produces a stem will come out from the root and it will turn into a tree, and then that tree will produce more roots, and then it will also have a rammit, so a stem that comes out. It's all all the same genotype. They're all connected by their roots and can take up over one hundred acres of land, and it's all the same genotype. And so you know, you can say, okay, well that doesn't really match how I think of an individual, and so it's cheating to say that you get to count all of that living stuff. But they can live for like ten thousand years, we think, And so you know, if you're willing to count that as an individual because it's all the same genotype, it has all the same genetic makeup. I'm sure there's some mutations in there, but you know, very similar. Then that can live for up to ten thousand years.
Well, that's interesting and really challenges your philosophy of like what is an individual? I mean, if we had human cloning and you turned eighty five and we decided to make a new Kelly, would you consider that Kelly to be the same as you? And then when you died, you feel like, no, I'm still alive.
I see your point, But like this tree is able to do that with no help, Like it's incredible to me. And they're also able to produce seed, so they can produce this way, but they can also produce seeds that can go off and start this whole thing, you know, going somewhere else. I think it's an interesting philosophical debate about whether all of those trees and one hundred acres counts as the same individual or not. But one way or another, it's an amazing evolutionary strategy to replicate an organism's genes and get them spread throughout the environment.
I guess it does depend on what you consider to be the individual, because in my case, to feel like I'm still alive, I would want to keep my memories, my personality, all of my experiences, and I feel like butt off a new Daniel on my elbow probably wouldn't have all those experiences, and so it wouldn't really be me even if it had the same genotype. So this whole nature versus nurture aspect, Yeah, fascinating. Wow.
Yeah. So the listener wanted to know why do humans not live as long as trees? And I think the answer is that trees have just gone down such a different evolutionary path than humans have that they are able to sort of die incrementally and sort of really stretch the process out. There are a lot of pieces that all need to be working in order for our bodies to keep going, whereas trees are able to do things like compartmentalized to eke out in existence for a lot longer.
Yeah. I'm sometimes surprised that I'm living as long as I am when I have all these bits that all have to work all the time. Yeah, and they all seem sort of complicated, like we are a very elaborate meat machine. It's amazing that we keep going as long as we do.
I absolutely agree. And it's amazing that we don't encounter even more problems along the way, given how many things have to go perfectly in order for us to continue existing the way we do well.
One thing that I think humans will continue to do as we age is to be curious about the world and to wonder and to build knowledge. And I'm just glad the human knowledge builds from generation to generation. We can path this down. You don't have to be five thousand years old to have five thousand years worth of knowledge because we're able to inherit it from all the folks that were curious before us.
Yes, And it became so clear to me while researching this just how important that knowledge is and how it builds on each other and how you know, dendro chronology, which is the aging of trees helps you with archaeology. And it's just we're very lucky to have all of this cultural ability to transmit knowledge.
It is incredible, And I love the depth of nerndomb that existed so many little facets of science, you know, people who have figured out how this works for trees and helps us in other areas like that requires an individual to be like super fascinated by this topic and devote their life to it. And wow, I'm just so grateful that there are people out there who are curious and pushing knowledge forward. In every direction simultaneously.
Thank you for being curious and listening to our show, and we hope to see you at the next episode.
Tune in next time.
Thank you for answering my question. You answered it really well, and it's how trees can be alive and some places and data and other places at the same time.
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