Aug 23, 2015

How old are you? Or more precisely, how old are your cells...the cells in your liver, or your spleen, or your brain? It's a question that's harder to answer than you think. That’s because some cells are born after you are, sometimes many many years after, but we’re not really sure which ones, or when — it’s not as if there are cellular birthday parties, marked by balloons and cake. So the question of age remained relatively unanswered until the early aughts, when scientist Jonas Frisén, inspired by work from researcher Bruce Buchholz, had an idea: what if we just look up? In this story, producer Molly Webster travels back in time, to the Cold War; way up into the atmosphere; and deep inside our cells, where a secret little signal, from a very special type of carbon is helping to answer the question: how old are we? But it’s a journey that is pressured by time. 
Special thanks to Mark Lovell, Henrik Druid, Laura Kiessling, Phil Newmark, Marc Kirschner, and Thomas Pollard 


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Jad: Next up, producer Molly Webster and Carbon.

Molly: All right.

Jad: Okay. I'm just going to launch in.

Molly: Science.


Molly: This is my new thing with my sisters, I just always go #science because they get really sick of me trying to teach the kids sciencey lessons.


Molly: Just #science it. One of the biggest mysteries in biology is, "How old am I?"

Jad: That doesn't seem like a mystery. [chuckles]

Molly: I mean, obviously, I'm Molly Webster who is 32 years old. Who has lived through 32 birthdays, I guess, but this is a question of, we know that some cells in our body regenerate. It's like, how old are those cells? How old is my heart right now? How old is my eyeball or how old is my nose?

Jad: And spleen.

Molly: The northwest corner of my kidney?

Robert: Is this like if I'm three years old now, I'm 33 years old, do the cells in the 33-year-old, is any of them the same as the one when I was three? Is that the question?

Molly: Yes. That's one of the questions. Are any of them the same? If they're not the same then how often do they change? If you understand that then you might be able to solve injuries, help people heal faster, or fix diseases where cells are messed up, like psoriasis or anemia or ALS or something like that. Also, it would seem so cool to be like, "Oh, that chunk of my heart is from 1997 or that other chunk of my heart is from 1983. Like that--

Robert: I'd love to know that. At the party of Robert, I would want to meet the original Robert cells. If there's anybody who has been here since 1947, I'd love to just say hello and if you just joined me in 2015, well, that's nice.

Molly: Right, it would be super cool. One of the questions they've had for a long time is, is there a way that we can try to date cells? We can't really send anything into the body because that can be toxic. The answer for a long time had been, no. Then 2002-ish, this little idea pops up. It's something called the bomb pulse.

Robert: B-O-M-B, bomb?

Molly: B-O-M-B and then pulse, P-U-L-S-E.

Jad: Bomb pulse.

Molly: Yes. To explain.

Speaker 1: Five, four, three, two, there it goes.

Molly: In the 1940s and '50s, we all know this.

Speaker 1: [unintelligible 00:02:49] there is the ground wave. It is over folks.

Molly: We tested a lot of atomic bombs.

Speaker 1: It worked. It worked. There's a huge fireball.

Molly: The first test was in 1945, Trinity test, New Mexico. A few weeks later-

Speaker 1: The world will know that the first atomic bomb was dropped on Hiroshima.

Molly: Hiroshima and Nagasaki.

Speaker 1: We shall continue to use it.

Molly: Then as World War II comes to an end, the rest of the world just tries to catch up to the US.

Speaker 1: The Redshad to explode a huge bomb of 50 megatons.

Molly: The Russians.

[Russian language]

Molly: Then after the Russians-

Speaker 1: Britain fires its first H-bomb.

Molly: -the British, the French, the whole Cold War basically just continues to unspool. All in all, over 400 atomic tests went off above ground between 1945 and 1963.

Speaker 1: Just imagine, if only one atom was to be dropped on an American city. Thousands of persons would be killed instantly.

Jad: That was a sucky time.

Molly: Well, #science. There was one good thing, potentially one good thing popped out. That is an answer to the question of how old are we.

Jad: That somehow came out of the bomb test?

Molly: Yes.

Jad: How?

Molly: Let me explain.

Jad: Do it.

Molly: With every one of those detonations, when an atomic bomb goes off it would shot a whole bunch of stuff up into the atmosphere. All of these radioactive elements, like CCM and plutonium, and all these things. Also, that explosion shots up a bunch of neutrons. The neutron will crash into nitrogen that's floating in our atmosphere and create C14 which is a very special type of carbon. It has two extra particles in it.

Now, as all that bad radioactive stuff starts falling out of the atmosphere back to the ground, C14 doesn't fall out of the sky. It just floats there. What happened is over time, the wind currents carried C14 from these test sites and just spread it all over the planet. This C14 which is just totally like normal carbon, not harmful, it just bonds with oxygen and it gets sucked up into plants. Then animals eat the plants. Then we eat the animals or we eat the plants. Then suddenly the C14 is in us. We all have a little bit of the atomic age in us.

Jad: Wait, but I wasn't even born in 1963, so why would it be in me?

Molly: That is the cool thing because it hangs out in the air for a long time, so it's actually still up there.

Robert: Why does this have anything to do with dating anything?

Molly: Yes, I'm about to tell you that. Hey, are you there?

Jad: Hi. Yes, I am.

Molly: Perfect.

Bruce: I'm Bruce Buchholz. I'm a senior scientist at Lawrence Livermore National Lab.

Jonas: Jonas Frisén, Professor of Stem Cell Research at the Karolinska Institute in Stockholm.

Molly: In the early 2000, Jonas is staring down this question of, "How do I date cells?" At a certain point, he gets together with Bruce because he comes up with this idea which is just, "Oh, maybe we just look up."

Bruce: There are some groups in Europe, there's one, in particular, that's been measuring the atmosphere every two weeks since the late 1950s.

Molly: Oh my God.

Bruce: It's an incredible data record.

Molly: Bruce says what these scientists have done is, they've taken all of these measurements and they put them into one chart so you can see the amount of C14 in the atmosphere over time.

Bruce: We have this, basically, a calendar. I could send you a picture so you'd see what the graph looks like.

Molly: Yes, I'd love to see a picture. What you see on that graph is this, according to Jonas.

Jonas: Up to 1955, it's a pretty flat line with very little variation. Then suddenly in 1955.

Molly: With all the bomb tests.

Jonas: There's a very sharp increase.

Bruce: A lot of carbon14. Very drastic increase. That's why they called it a pulse.

Molly: That increase goes all the way up to 1963 when--

Speaker 1: The Kremlin, fortress of communist doctrine is the setting of an historic event.

Molly: When the US, the UK, and the Soviet Union agreed to stop exploding atomic bombs above ground.

Speaker 1: The signing of an atom test ban.

Jonas: After that, there's a [unintelligible 00:07:05] decline.

Molly: They're just measuring it all the way down. They can just say, "Oh, here is where it was in 1980. Here is where it was in 1990, 2000, 2010. This right here is the coolest part because the amount of C14 in the atmosphere at any given moment is directly reflected in our cells. If there's that much C14 in the atmosphere in September 1972, then that is going to be mirrored in cells that were born in September 1972. It is like this totally perfect birthday calendar.

Bruce: We can see approximately how long. Have they been there for 10 years or 20 years or 30 years?

Molly: Once this idea got out, scientist all over the world were like--

?Bruce: Oh, yes.


Oh, give me your attention,

there's been a new invention.

Bruce: It didn't take long to see that this might be something cool to do.


It came about because they made a big atomic bomb.

Molly: Just to give you a quick sense of the work that came out of this, I spoke to one scientist.

Kirsty: I'm Kirsty Spalding and I work at the Karolinska Institute in Stockholm.

Molly: She was working with Jonas and they figured out how to use C14 in brains.

Kirsty: First of all the basic question was, "Can adult humans make new neurons?"

Molly: She said that for like 100 years-

Kirsty: The dogma had always been that the neurons we're born with are the ones we die with.

Molly: The problem was she had no way to investigate this. She couldn't use it in humans, even if they were dead humans until she figured out a technic where she could extract brain cells and see how much C14 was in there.

Kirsty: Yes, exactly.

Molly: It turns out, the next best thing to human is a horse.

Kirsty: Because horses can live for quite some years.

Molly: Decades.

Kirsty: Every second Tuesday, I would go out to the local abattoir.

Molly: The local slaughterhouse.

Kirsty: Narrow way. I was a vegetarian surrounded by carcasses and they would bring the horse's head out to me and I had to figure out how to get the brain out of its head.

Molly: Wait, what? You actually had to cut open the skull and get to the brain yourself?

Kirsty: The second time I went, I took my boyfriend with me. I was like, "I can't do this." Physically, they actually have a circular saw and I actually discovered that the skull, the bone across the top, the nose of the horse is quite thin. That was a much easier access point.

Molly: This is a really gross discussion. Did you ever see your research going that way?

Kirsty: No, absolutely not. Not at all.

Molly: What she saw when she finally moved her research from horse heads to humans was turnover.

Kirsty: We found quite robust levels of new neurons in adulthood.


I tic, tic, tic, why do I tic, tic?

Molly: Once Jonas' team showed that this worked, scientists got excited and people started to date things and not just cells. Can I tell you the ages?

Robert: Sure.

Speaker: Okay. The baseline ages we knew before C14 was that skin was 14 days old.

Robert: 14. Oh, that's only 14 days old?

Molly: 14 days, yes. It's like two weeks. The surface level of your gut, the skin on your gut I guess, was five days.

Robert: Five days.

Molly: That's even shorter than skin because that's the surface of the intestine.

Robert: Wow. Oh, the surface of the intestine?

Molly: Yes.

Robert: The lining.

Molly: The lining.

Robert: Because that's everything. Scrapping all that food going down. No, that doesn't surprise me.

Molly: Then, with C14, the deeper muscly part of the intestine, the average is 15.1 years.

Robert: 15.1 years. Oh, big difference between-

Molly: Wait, 15.9 years old.

Robert: Okay, 15.9 years.

Molly: Fat cells was another one that they did. 10 years old.

Robert: 10 years old. Interesting.

Jad: Why would a fat cell need to last that long?

Molly: 10 years?

Jad: Jesus.

Robert: Because it's perverse.

Molly: Just to torture you.

Jad: Why would it last that long?

Robert: Fat cells are mean cells.

Jad: Honestly, do they have any idea?

Molly: They don't know.

Jad: Do they know what would be the oldest part of us?

Molly: Your cortex, which is the part of your brain that does abstract thinking or your voluntary movements. That's as old as you are.

Jad: Really?

Molly: If you want to know one of the oldest parts of you, the oldest cell is probably in your--

Robert: Super think part of your brain?

Molly: It will be your cortical neurons.

Robert: That fits if I think of myself as the stories I tell myself. Like when you get Alzheimer's and you lose your stories, you lose your mind like people say.

Molly: The interesting thing now is the hippocampus is where you keep all your memories. They saw that your hippocampus does make a bunch of new neurons.

Jonas: In the hippocampus-

Molly: That's Jonas Frisén, again.

Jonas: -an adult gets approximately 1,400 new hippocampal neurons per day.

Jad: Really?

Molly: Yes. Then each of those neurons will live 20, maybe 30 years.

Jad: Does that mean that the part of Robert's brain where he keeps the stories he tells himself, that part is being made new every 20 or 30 years?

Molly: Yes.

Jad: It's a strange thing. Your oldest stories could be stored in baby little neurons.

Robert: That is weird. I remember going to Kyoto. The oldest, most beautiful temple in Kyoto, it has exactly the form that it had hundreds of years ago, but when you walk in, the walls and the floors, and the roofing, they've been restored. They've been restored actually, over and over again because in Japan, what they call old is the form. It's the shape of the building.

Go to Athens though, and you go up to the Acropolis and stand in the Parthenon, there, you're standing in the very temple that Pericles stood in. It's the same place exactly, same materials. In Greece, they believe that the original stuff is what you preserve and in Japan, they think it's just the form. I was thinking that this thing you're doing is like that. I was thinking, "I'm much more Greek than I am Japanese."


Robert: Because I want to know what my original cells are, where they are in me.

Jad: My question is more basic. It's like, why does a part of me get reborn and the other parts of me don't? Why not all of me get to be reborn?

Molly: Because if all of you is being reborn, you'll just crumble into dust. [crosstalk] [laughs]

Jad: Why does only certain parts get to regenerate?

Molly: It's interesting because they don't know. They said, basically, this question of, how old is a cell? They said no one was asking. Everyone wondered this, but no one was asking this question because they never had the tools to ask it. Now they're just starting to ask those questions, but there's a problem. This bomb pulse that we've been dependent on in the last decade to start answering all these questions is going away.

Jad: Really?

Molly: Every day, a little more of that C14 gets sucked out of the air.

Robert: How much time do we have left?

Molly: 15 years. It's gone by 2030, give or take.

Kirsty: We need to get questions answered now because we really are working against the clock for many things we want to look at.

Molly: I talked to this Alzheimer's researcher who's trying to figure out the chronology of the disease. When certain pathologies form in the brain, and he was just like, "I just wish I had a little more time." I was thinking about this on the subway this morning. I was looking around and I was thinking. I'm on the L-train, it's a bunch of 30-year-old kids or something, and they're all reading or something, drinking their expensive lattes.

I'm like, "These people are so far away from thinking about the Cold War, or atomic bombs, or anything like that and they're all walking around with the secret signal from the atomic period inside of them. Then, that little signal is beaming out knowledge about their shoulder, and their elbow, and their liver, and the west side of the liver, and the east side of the liver, and different parts of the heart." The fact that it's now going away and how someone born in 2042 is just going to be really boring.


Molly: We know they're not going to have any insight into who they are. It makes me inclined to, very peacefully, want to explode another atomic bomb.

Robert: What? No. No, no, and no.

Molly: Why?

Robert: You forget of all the poisons that it-- That is not a benign event that's an experimental picker-upper. That is extra, extra stuff in the air.

Molly: Don't kill my dream.

Robert: I have to kill your dream because it's a dumb, dumb dream.


Lord have give us a great new power,

For to use for the good of all mankind.

Some people gonna use it to destroy everything,

Bu-hut God didn't mean it like that.

He wants it used for the good of all mankind.

Oh I have talked to Jesus,

(Oh the a) -tomic telephone

(Well uh then) no man know the power,

(Oh oh oh) only God alone.

(Oh well then) it can cure the sick,

Or destroy the people.

With one sweep of power,

Known by God alone.

Jad: Producer Molly Webster.

Robert: Special thanks to Henrik Druid and Mark Lovell.

Sam Breslin Wright: Happy Valentine's Day, magnesium. I go blind watching you burn, magnesium. Iodine is cute the way it sublimates. Yes, I'll put lithium in water to watch it scoot about, but my heart belongs to you, magnesium. The hot white flame, the abandon, the slowness of you becoming your own fuse. Mercury is beautiful, yes, but it's you, magnesium. The way you burn for me. The way you leave nothing of yourself behind.

Joniece Abbott-Pratt: We are flying over Greenland. Your elbow is too close to mine on the airplane armrests. Down there, they are excavating uranium from beneath the arctic ice and selling indiscriminately. Though from here, I can only see the white of ice sheets in glacier-topped mountains. This is an island of fishing rigs and colorful houses, cod and catfish stew and tomato cream. Once, I thought every isotope in me is radioactive. I make the people who love me sick. This is a teenage way of thinking. You have uncovered a glowing spark in the pristine frozen places within me.


Jad: That was Uranium from poet, Emily Hockaday read by Joniece Abbott-Pratt. Before that, Happy Valentine's Day, Magnesium by Jason Schneiderman performed by Sam Breslin Wright.

Robert: Everybody has a middle name in this thing. Sam Breslin Wright.

Jad: Yes, they do. Coming up-

Robert: We're going to get into an elevator, push the button, and go down, and I mean all the way down. I'm Robert Louis Krulwich.

Jad: Jad Nicholas Abumrad. We'll continue in a moment.

Pilar Castro: Hi, this is Pilar Castro from Bogota, Colombia. Radiolab is supported in part by the Alfred P. Sloan Foundation, enhancing public understanding of science and technology in the modern world. More information about Sloan at Muchas gracias, Radiolab.


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