Science Friday - Historic Big Bang Debate, Black Hole Sounds, Plant DNA Mutations. Jan 14, 2022, Part 2

Episode Date: January 14, 2022

A Debate Over How The Universe Began Even though it’s commonly accepted today, the Big Bang theory was not always the universally accepted scientific explanation for how our universe began. In fact, the term ‘Big Bang’ was coined by a prominent physicist in 1948 to mock the idea. In the middle of the 20th century, researchers in the field of cosmology had two warring theories. The one we would come to call the Big Bang suggested the universe expanded rapidly from a primordial, hot, and ultra-dense cosmos. Conversely, the so-called ‘Steady State’ theory held that the universe, at any given point in time, looked roughly the same. The story of how the Big Bang became the accepted theory of physics is also a story of two men. One, Fred Hoyle, was a steady state supporter who thought the universe would last forever. Meanwhile, George Gamow, the major public advocate of the Big Bang, begged to differ. They debated in the pages of Scientific American and in competing popular books, as both dedicated scientists and earnest popularizers of their field. And while Gamow ended up winning the debate, for the most part, the two men managed to come together in one way: They accidentally explained the origins of every element of matter by being part right, and part wrong. The truth, it turned out, would lie in the middle. Ira talks to physicist and science historian Paul Halpern about this story, detailed in his book, Flashes of Creation: George Gamow, Fred Hoyle, and the Great Big Bang Debate.   The World According To Sound: Listening To Black Holes Collide In this piece, you can actually listen to gravitational waves, the ripples in spacetime made by the tremendous mass of colliding black holes. It is possible to hear them, because their wavelengths have been shifted all the way into the human range of hearing by MIT professor Scott Hughes. Drawn together by their immense gravity, nearby black holes will swirl faster and faster until they are finally absorbed completely into one another. When the pitch rises, it means the force of gravity is increasing as the black holes collide. Not all black holes come together at the same rate or release the same amount of gravitational waves, so each combining pair has its own particular sonic signature. Some black holes collide quickly. Others slowly merge. Some produce relatively high pitches, because of the intensity of the gravitational waves, while others have a low bass rumbling. Some even make the sound of a wobbling top as the two black holes swirl around each other, before eventually meeting and becoming totally absorbed into one another.   Is There A Method To Plant Mutation? Mutation is one of the cornerstones of evolutionary biology. When an organism’s DNA mutates thanks to damage or copying error, that organism passes the mutation on to its offspring. Those offspring then become either more or less equipped to survive and reproduce. And at least until recently, researchers have assumed that those mutations were random—equally likely to happen along any particular snippet of a piece of DNA. Now, scientists are questioning whether that’s actually true—or if mutation is more likely to occur in some parts of the genome than others. New research published in the journal Nature this week looks at just that question, in a common weed called Arabidopsis thaliana. After following 24 generations of plants for several years and then sequencing the offspring, the team found that some genes are far less likely to mutate than others. And those genes are some of the most essential to the function of DNA itself, where a mutation could be fatal. Conversely, the genes most likely to mutate were those associated with the plant’s ability to respond to its environment—potentially a handy trick for a highly adaptable weed. Lead author Grey Monroe talks to Ira about his group’s findings, why this skew in mutation likelihood may benefit plants like Arabidopsis, and why it may be time to think differently about evolution. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Ira Flato. Believe it or not, even though it's commonly accepted today, the Big Bang theory was not always the universally accepted scientific explanation for how our universe began. In fact, the term Big Bang was coined by a prominent physicist to mock the idea. Here's some background. In the middle of the 20th century, researchers in the field of cosmology had two warring theories, two opposing theories. One we would come to call the Big Bang, where the universe expanded rapidly from a primordial hot, ultra-dense cosmos, versus the so-called steady-state theory, where the universe at any given point in time would look roughly the same. The story of how the Big Bang became the accepted theory is also a story of two men. One, Fred Hoyle,

as steady state supporter, who thought the universe would last forever, and you, George Gamov, the major public advocate of the Big Bang, who begged to differ. They debated in the pages of Scientific American in competing popular books. In fact, Gamov's Mr. Tompkins series was my favorite book for understanding relativity as a child. And he turned out to be right for the most part, and Hoyle, despite as many other achievements, is remembered not for his stellar work as a dynamic scientist, but for giving the theory the derisive but popular name, Big Bang. As always, there is much more to the story. And here to take us back in time is Dr. Paul Halpern, Professor of Physics at the University of the Sciences and author of a new book, Flashes of Creation,

George Gamov, Fred Hoyle, and the Great Big Bang Debate. He joins us from Philadelphia. Welcome to the program, Paul. Thank you so much for having me on Science Friday. Nice to have you. First, let's set the scene of what we knew about the universe at the time these two men was supporting opposing theories? Why was the origin of the universe in question at all at that time? Well, the origin of the universe scientifically was first examined by Albert Einstein when he developed his general theory of relativity back in 1915. And Einstein found that his theory produced a rather strange solution that would expand over time. And at first he thought the solution was a big mistake. But then later after Edwin Hubble and others mapped out the behavior of galaxies in the

universe and saw that all the galaxies except the nearby ones were actually moving away from us faster and faster, that meant that the universe was expanding. And Albert Einstein realized that the universe was growing after all. It was a dynamic cosmos. So then people such as George Lamatra, who was a Belgian priest and astronomer, speculated that the universe came from something called a primeval atom or something that included all the matter in the cosmos, and that expanded many, many billions of years ago and formed the present-day universe. And then people start to think, well, are there alternatives to the idea of the universe expanding? And one motivation for that was when they used Hubble's data to try to estimate the age of the universe, they came up with

two billion years or three billion years, much less than the age of Earth or the age of stars. So there seemed to be a blatant contradiction between the data they found and the present-day knowledge of the universe, the fact that the universe must have had existed before stars were produced. And that's when Fred Hoyle came up with the idea of the steady state universe, which expands but new matter fills in the gaps so it lasts forever. And why was Fred Hoyle so sure that he was right that the universe was in this steady state? Well, Fred Hoyle was a very instinctive scientist, and he actually came up with the idea of steady state,

along with two other scientists, Herman Bondi and Tommy Gold. After seeing a movie, it was a horror movie called The Dead of Night. And that film has a plot in which the beginning of the film, and the end of the film are pretty much the same. Somebody goes to a house and realizes that he experienced the house in his nightmares, later wakes up and the whole thing turns out to be a nightmare,

but then he's invited to the same house again, and everything happens over and over again in the film. And after seeing that film, they went to Herman Bondi's apartment, and Tommy Gold said, well, what if the universe is like that? So they put their minds together, and Fred Hoyle came up with the idea

of continuous creation, that small amounts of matter would pop up in the universe very, very slowly over time, and that matter would eventually form stars and galaxies and repopulate the areas where older galaxies move away from. And Hoyle thought that was a much more satisfactory idea of explaining the universe than the Big Bang, because instead of having all the matter created at once, which he derided when he coined the term the Big Bang, he thought that it made more sense to think of matter coming in so slowly that it was undetectable, and therefore science would not be defied. I have to take a sidetrack here and ask you, if you think it's unusual in your experience as a physicist and a scientist, to find that inspiration comes from

a science fiction horror movie? It is unusual, but it's a rather delightful story. And who knows they might have been thinking about that in other ways, but looking back, they attributed their discovery to the movie. But people get inspiration in so many ways. There's a story about Leo's Alar, thinking about the chain reaction by reading a science fiction story by H.G. Wells and coming up with the idea. So people are sometimes inspired by science fiction. Wow, that's a great story. And Gamov, where did the idea for the Big Ben, from? Well, Gamoff took up the idea from others. He was a student of somebody named Alexander Friedman, who developed one of the first solutions to Einstein's equations. And like Einstein's

original solution, Friedman saw that general relativity can lead to an expansion of the universe. And Friedman did not shy away from that hypothesis, even though there was no real evidence for it at that time. And Gamov was in Freeman's class at the University of Leningrad. And Gamov was inspired by Freeman. And later, when he developed ideas in nuclear physics, start to think about developing a theory about how all the elements are created. So we decided to combine the idea of nuclear fusion and the idea of the hot early universe and come up with a theory that all the elements in the universe are created at the fiery beginning, which later became known as the Big Bang. And Fred Hoyle coined the term on a BBC TV show, is that correct?

It was a BBC radio show that Fred Hoyle was invited onto to talk about his own ideas. And at that time, he wasn't really so much aware of Gamov's theories, which were pretty new, but he was aware of Lamatra's ideas and other ideas of the expanding universe. So he said, well, there's steady state. there's an alternative, which you called the Big Bang, and it used that to kind of say, well, isn't it kind of silly to think about the idea of all the matter being created in a colossal explosion? And explosions were pretty much on people's minds at the time, because it was only a couple of years after the first atomic bomb blasts, and people really didn't like the idea

of explosions. So it kind of derided the theory of people started associating it with explosions and bombs. You know, this idea that you just said, the idea that Fred Hoyle would go on the BBC radio and talk about it in public, this was not unusual for him or George Gamov, correct? They used the popular media to get their points across. They didn't just argue in scientific papers, but wrote popular science books and even science fiction. Did their ideas about the universe translate easily for the public? Well, I think that's one remarkable thing about both Hoyle and Gamov. It's because both of them were not only excellent scientists, and arguably each of them could have won the Nobel Prize,

but each of them was also an award-winning popularizer. They both won prizes for their popularizations, and they both loved Hollywood. Gammov loved Westerns, and Hoyle grew up watching movies because his mother played the piano in a cinema for silent movies. She was the accompanied this for these movies. So Hoyle grew up watching movies, and they both have a cinematic sense of how to convey science in a very evocative way. I was very interested in your statement, in your book that says, the epoch of scientists popularizing their own work for good or bad had commenced. No longer would theories be hidden in the pages of scholarly books and journals. This was a turning point, do you think? Yes. Well, the turning point came.

about because of new media. So first radio and then television. When people got early televisions in the 1950s, a lot of the reason they bought it is to see Milton Burrell and comedy shows. But then let's say they wanted an alternative. They might turn to a different channel and other stations would need material to fill the airwaves. So they would recruit scientists such as George Gamov to talk about their theories. And that, became the first science popularization on television. Of course, there was also the advent of paperback books. You mentioned in Mr. Tompkins series. In the 1950s, people started buying paperbacks, which are very inexpensive, and reading about scientific ideas and debating about them.

I still have my original copy of Mr. Tompkins from back then. You mentioned that for good or bad. What do you mean for good or bad as science popularizers? Well, sometimes valid scientific ideas would be overlooked in favor of something that was more marketable to the media. And a good example of that is that Albert Einstein in his later years developed all sorts of theories of everything, which were not experimentally proven. There was no way of verifying them. And theoretically, they were dubious. And yet, because Einstein was so famous, they would attract colossal media attention. The media would fight over the right to publicize Einstein's theories,

even knowing that physicists were not really embracing them. In fact, physicists were running away from those theories in favor of things like quantum electromagnatics, and that got no media coverage at all. You also talk about apocalyptic theories, not on the Einstein level, but about the arrival of Halley's comet being, well, very, dangerous for us. Yeah, well, actually, when Gamma was a little boy, Halley's Comet arrived on its periodic journey. And there was a popular science writer, Camille Famillion, who had speculated

that Halley's Comet had a atmosphere that would be poisonous. It turned out that it was, you know, a minimal amount of something that could potentially be poisonous in millions and millions of times, more concentrated amounts. So it was completely safe, but there was a mass panic because of that. So people were afraid of Halley's Comet in 1910. We have to take a break, and when we come back more from Paul Halpern about George Gamov, Fred Hoyle, and the Great Big Bang Debate. You're listening to Science Friday. We're talking with physicist and author Paul Halpern about his latest book about the disagreements of two once-ren science communicators and physicists in the middle of the last century. On one side, George Gamov,

champion of the Big Bank theory, and on the other side, Fred Hoyle, who thought the universe existed in a steady state rather than one sudden burst of matter and energy. I'd like to go back to the ways in which these scientists were different in so many ways from the classic stereotype. You're right about Hoyle. Quote, throughout his life, he argued strongly that scientists should be literate, proving his own thesis by writing or co-writing numerous well-regarded science fiction books that blended thought-provoking science ideas with intriguing social issues. You point out that he wrote an opera about Copernicus. He speculated about alien life in his novels, The Black Cloud and Afer Endromeda. Wouldn't you say he was a Renaissance man? Yes, both Hoyle and

Gamov were Renaissance people. They really believe that culture was just as important as science. He mentioned, wrote the libretti for operas. He really believed in trying to explore all the facets of life. He was an avid mountain climber, and Gamov loved to travel and love to hike and go on motorcycle rides. So they really disproved CP Snow's conjecture about two cultures not communicating with each other, science and the arts. And in fact, C.P. Snow was the one who invited George Gamow to write for a magazine called Discover Magazine that later led to him writing the Mr. Tompkins series. Yeah, you're right that his numerous popular books and articles contain clever sketches and wordplay, it poked fun at his field in puns and parodies.

I feel like I would have gotten along with him pretty well as a pun appreciator myself. Let's go back a bit to talk about the resolution of the Big Bang argument. As we know, it's the theory that won and is most widely accepted today, what was the evidence that eventually tipped the scales? Well, things were trickling in in the late 50s and early 60s, such as, for example, the discovery of quasars, which turned out to be very young, active galaxies, and formation, colossal sources of energy, but you only see them in the distant past. You don't see them in the present, which suggests that the universe evolves. But the real smoking gun was in 1964 and 1965 when two scientists, Arno Penzias and Bob Wilson,

who had borrowed a communications satellite radio detector, had converted it to use to detect astronomical radio waves, looking at radio waves in the halo of the galaxy, trying to detect those. And they got this unexpected hiss, and they thought maybe it was ambient radio noise or something from New York, which was nearby. They thought it might be the droppings of pigeons. And they called that a white dielectric material, which they scraped off the detector. After they had scraped it off and captured all the pigeons, and those pigeon cages are in the Smithsonian. after doing all that, they still saw the hiss, or heard the hiss, I should say, in all directions. And they had a contact that knew that somebody named Bob Dickie at Princeton was working on a radio detector himself.

And that's because Bob Dickie had this theory that the universe had previous eras in which radio waves could be left over from previous cycles of the cosmos. And that theory predicted that there would be this cold radiation out there. And Dickie was about to build a detector to try to test for that. And when he heard about Arno Penzius and Bob Wilson's discovery, they drove out there, they looked at the detector, they looked at the evidence, and they said, well, this is evidence of radiation from the early universe. And Dickie's associate Jim Peebles immediately did an analysis showing that the theory of the hot big bang predicts radiation at exactly that temperature or approximately that temperature, I should say, of 3 Kelvin, which is 3 degrees above absolute zero. Peebles later found out that Ralph Alfer, who was a student of George Gamov, had done a similar calculation back in the 1940s.

So then after Peebles and Dickie announced the result, and it was all over the press, it was headlines in the New York Times, then George Gamov and Ralph Alfer piped in and said, hey, wait a minute, we did stuff like that back in the 1940s. Perhaps we should get some credit for it. Did Hoyle ultimately accept this conclusion? He briefly went through a big bang phase. He thought, well, maybe there's some validity. to the Big Bang and thought about that for a couple of years. But he was so proud of the steady state theory and saw it so elegant the idea that the universe could last forever, that eventually he and several other physicists developed an alternative called the quasi-steady state. And then the quasi-steady-state theory, something else called iron needles, which permeates space. A little bit of a hokey idea. But they absorb radiation and rebroadcast it at just the right temperature that the satellites and other instruments

predict for the microwave background radiation temperature of the Big Bang. But also they said that the helium produced in the Big Bang, which was another prediction, could be produced in galaxies instead. So they eventually had their own theory, a variation of steady state, and they held that that theory was valid and to the end. And if somebody questioned Hoyle, he said, well, look, you always have to have alternatives. You don't want to be the geese following the herd. And in his last book,

Hoyle had a photo of a mother goose leading a herd of geese to who knows where. And he thought that Big Bang physicists were exactly like that. They were just following the leader blindly without thinking whether or not the Big Bang was right, but just doing it because it was fashionable. And Hoyle thought that at least you have to entertain alternatives. Great story.

I know that these two scientists disagreed about the fundamental trajectory of the university. We've just been telling us about that. But collectively, right, they managed to explain the origin of about every element of matter. Gamov thought that Big Bang could explain everything from hydrogen up until gold and beyond. Hoyle thought all matter was created inside stars. and they were both wrong and they were both right. That's correct. So Hoyle came up with a theory called stellar nucleus synthesis,

which says that stars build up the elements during different processes. And one process happens when hydrogen is no longer being burned in the stars, and the stars start to contract, and helium is burned to produce carbon. And then as the stars continue to contract, they get hotter and hotter, and produce the higher elements. Once they reach iron, stars undergo supernova explosions if they're massive enough, and the rest of the elements are produced in the supernova explosions.

And the original elements that were produced are also released in the supernova explosions, which is why the great Carl Sagan said, we are all made of star stuff, because everything in our bodies, except for the hydrogen and helium, everything around us, I should say, was produced in stars and released during supernova explosions.

But the amount of helium in the universe can only be explained by postulating that was produced in the Big Bang. But it turns out that the higher elements could not have been produced in the Big Bang because it cooled down very rapidly and was not hot enough to produce any elements beyond helium. So it turns out that Gamov developed the beginning of the story from hydrogen to helium. And Hoyle and his colleagues developed the end of the story, starting with the elements beyond helium. You know, it's interesting that neither of these men won a Nobel Prize for the physics work, even though what, they contributed to this breakthrough in our understanding of where matter came from. How would you hope the field of cosmology remembers their contributions?

Well, interestingly, I guess Gamov could have won the Nobel Prize, but he died very, young. And at the time when he died, they weren't really giving too many prizes out for astronomy and cosmology. That became a relatively new thing later on, and then starting in the 1970s. And Hoyle really should have won the Nobel Prize for stellar nuclear synthesis, but in his later years, he came up with certain fringe theories that were very unpopular. And I speculate in my book, flashes of creation, why Hoyle didn't get the prize. But another reason might have been that they thought the person who tested the theory came up with the theory himself. And that was Willie Fowler, who started testing the theory along with two other people, Jeff Burbage and Margaret Burbage,

who are husband and wife. And that team, which are called B2FH for short, developed stellar nuclear synthesis as a whole, but they can only give the Nobel Prize for three people maximum, and they ended up giving it only to Fowler, which was a great disappointment to those who knew Hoyle came up with the idea originally. Let's sum this up and talk about this book being about two creative mavericks with big personalities, and you write that there isn't necessarily room for such people in physics as it is studied today. And you say that physics like other sciences is collaborative and team-driven and relies on big data? Is this a good thing overall for the progression of the field? Well, when Gamov was working, and to some extent when Hoyle was working,

it was possible to take some paper, for example, in quantum physics, and apply an equation to something else and work out the results overnight and publish it and have a ground-baking discovery, but that era seems to be gone, and that's because in the 1920s and 1930s, there were so many discoveries in fundamental physics, and that kind of slowed down from the 1940s until the 1960s. And it's sad that today, there aren't so many discoveries in fundamental physics. There are discoveries in applied physics, such as a biophysics, condensed matter, and so forth, which are equally important. But in fundamental physics,

there aren't enough experimental discoveries to justify continuing to come up with new theories. So that's why today, physics is done in big labs with giant experiments, such as the LHC experiments in Switzerland. So the experiments require huge teams. And in terms of theories, it's unlikely that a single person, will come up with a breakthrough based on all of the evidence out there and the difficulty in progressing beyond what we know. It just seems like it's a daunting task and requires many, many, many

calculations and many, many, theories, not just a single person. And yet we still have these great mysteries about cosmology, about the universe. I'm talking about dark energy and dark matter, which make up 96% of the universe, and yet we have no idea what they're made of. Is this not something fitting for a Maverick to come along and discover? Yeah, that is true. In cosmology, if somebody could come up with a valid explanation for dark energy or dark matter, that would be absolutely amazing, and that would be cause for celebration and a possible avenue for somebody who's an extremely gifted Maverick to make a breakthrough. So pay attention young people. That's an area where maybe you

can make a mark in cosmology trying to explain dark matter and dark energy. This is Science Friday from WNYC Studios. In case you're just joining us, we're talking to science writer and physicist Paul Halpern, author of the book Flashes of Crowsows of creation, George Gamov, Fred Hoyle, and the Great Big Bang Debate. Any other thoughts that you have about these two giants of their fields or about where we're headed in physics now? Well, I think it's remarkable that they were able to do so much and accomplish so much in so many different fields. And Gamov even made a contribution to the science of genetics. He came up with the idea that RNA can encode amino acids in triplets, you know, that was pretty

amazing for him to speculate about that. He came up the basic idea of combinatorics. Other people develop the specifics, but it's remarkable that they could do so much in so many fields and also be some of the leading popularizers in their day. And I think today, unfortunately, people have to make a choice, either to be a groundbreaking scientist or a popularizer. It's hard for me to think of anyone who's been able to stay extremely active in science to the extent that those physicists did and also be able to be as prolific in terms of science and science fiction today. But it could be possible, but it's become increasingly unlikely, now the things are so specialized.

Yeah. Paul, I want to thank you so much for your time today. My pleasure. It was great being on your show. Great book, Dr. Paul Halpern, author of Flashes of Creation, George Gamov, Fred Hoyle, and the Great Big Bang debate. And now for something a little different, but still appropriately cosmic. We're going to listen to a sonic treat from the world according to sound podcast. Turn up your headphones and enjoy. These are two black holes smashing together. Here are two more.

We're hearing gravitational waves, the ripples and space time made by the tremendous mass of colliding black holes. We can hear them because their wavelengths have been shifted all the way into the human range of hearing by MIT professor Scott Hughes. When the pitch rises, it means the force of gravity is increasing as the two black holes collide. You can hear how these two black holes, wobble like a top as they come together. Drawn together by their immense gravity,

nearby black holes will swirl faster and faster until they are finally absorbed completely into one another. These sounds are part of a communal listening series. The World According to Sound is hosting this winter for tickets to their 90-minute binaural events. Visit the world according to sound.org. We have to take a short break, and when we come back, could we be wrong about a key assumption about evolution?

This is Science Friday. I'm Ira Plato. When you learned about evolution in school, the explanation likely sounded something like this. DNA mutates randomly. Some of those mutations make an organism more likely to survive and have offspring with the same mutation. Other mutations might make the organism less likely to survive so it dies out. So natural solutions, ensures that only the beneficial mutations end up carried on in a population. But researchers are increasingly questioning that first premise and asking if mutation really is random, or is the relationship between natural selection and mutation more complicated? You'll see what I mean here because new research appearing in the journal Nature this week

takes a closer look at mutation in plants. And as the team writes, their results suggest that the genome might not randomly mutate, but protect itself from mutations in some of the most crucial locations. Here to explain, I'm sure, better than I can, is Dr. Gray Monroe, lead author on the new research and an assistant professor of plant genomics at the University of California Davis. Welcome to the show. Thank you so much for having me, Ira.

Did I get basically that thumbnail, correct? That was excellent. I'm impressed. That was a very good thumbnail. I'll thank my eighth grade, Mrs. Feffer, for science teaching me that. Perfect. And the big premise is that mutation is random, right? But that organisms adapt because the bad mutations don't survive, the good ones do. So why are researchers like you starting to question that?

That's right. So, you know, thinking back all the way to our high school biology, we were told that mutations are random. And so this is something that even as a practicing geneticist and evolutionary biologists, I never really questioned until we were looking at some data that suggested something very different. So we have been looking at mutations in a plant called a rabidopsis. It's a little sidewalk weed. It's something that you could hold in your hand.

It's a small little plant. And it makes for an excellent model system that we use in the lab to study mutation. And so what we've been doing is sequencing the genomes of many individuals of this plant. with experiments we call mutation accumulation experiments. And when we look at the distribution of these mutations across the genome, what we're finding is a pattern that's definitely not random. So there are some places in the genome that seem to be protected from mutation more than others. And when we asked what kind of regions of the genome are those, what we discovered is that those are the regions of the genome that are most important for the biology of this plant.

And what regions were protected more than others? So when we look at a genome, it's made up of a lot of different parts. So some of the places in the genome are those responsible for coding for proteins. And proteins are, of course, the building blocks of all cells and organisms. And we found that the regions of the genome that code for genes have a much lower mutation rate than the non-gene regions of the genome, which we think of as less biologically important because they don't code for proteins. So we found that genes that code for proteins have lower mutation rates. And then when we compared genes, what we found is that genes that have the most essential biological functions have the lowest mutation rates among genes.

And so what this suggests is that the places in the genome that are most vulnerable to the mutation, the places where mutations would most likely have harm are the ones that are most protected from mutation. And so this is a very different idea of random mutation. that we traditionally think of in evolutionary biology. Well, would you think that this is something that the plant evolved to do to protect itself? That's exactly right. So what we think is that this is a strategy that has evolved, that this plant and other organisms likely have developed complex molecular machines to repair DNA, and that these DNA repair genes are possibly targeting certain regions

of the genome in preferential ways. Yeah. Is there a metaphor that you can compare this to the way we normally live? There is. So I like to think about the metaphor of the DNA in your genome representing the blueprint for a car, for example. The parts of the car are the proteins that make up a cell. And so if we think about a car, some parts are more important than others. So for example, the shape of the wheel is obviously a very important feature of all cars.

All cars need to have round wheels. And so whatever part of the blueprint tells the main. manufacturer to make their wheels round is a very important part of the blueprint, whereas part of the blueprint that tells the manufacturer what colors to make the car is possibly a less important feature. And so if we think about, you know, if we imagine having imperfect copying machines, and so this is analogous to DNA being damaged during replication, for example, we would need to go and check the copies of the blueprint to make sure there's no errors.

And this is analogous to DNA repair. And you might imagine that it would be. be advantageous to double-check the portions of the blueprint that encode for or provide the plans for the most important features of the car. So it would be very important to double-check that the page that tells the manufacturer to make the wheels round would be something that you would definitely want to make sure is correct. Whereas something less important, like the color can be allowed to change in ways that are not as harmful and possibly even beneficial. So does the plate have a mechanism then for making sure, for double checking that the wheels are still the same?

That's a great question. So the mechanism that we think is going on, and this is largely supported by some excellent work that's been done in the realm of cancer genomics. So obviously for cancer, understanding why mutations happen more often than not in different places of the genome is very important with interesting, important implications for human health. And so what they've shown and what we have found evidence that supports is that the structure of how DNA is actually organized inside of the cell is what governs where mutations are more or less likely to occur. So if you were able to zoom in inside of a cell, what you would find is that inside of the nucleus, the DNA is actually not just sort of haphazardly a tangle of DNA molecules.

It's actually organized and it's structured as coils around proteins called histones. And so these histones provide kind of the backbone for DNA inside of cells. And these histones can actually be modified with certain chemical marks. And what we found is that these chemical marks are not distributed randomly across the genome. There are certain chemical marks that are found much more often and almost exclusively inside of genes, inside of those regions that code for proteins. And these chemical marks are also more often found in these essential genes. So if we think going back to the car,

metaphor, these marks are more likely found in the regions of the genome that code for these essential parts like the wheel in the car metaphor. So if we think about it, it's kind of like if the blueprint was highlighted in certain places, if the wheel blueprint page had a highlight mark on it. This is essentially what's happening. And what we think is going on is that these chemical marks on the histones are providing the signal that's allowing DNA repair to go and preferentially fix mutations that otherwise would occur in these important regions of the genome. This leads me to ask that if the plant is going through mutations, wouldn't it have to mutate in the area it needs to mutate to protect itself to create these chemical markers?

Didn't it initially have to mutate to protect itself from mutation? That's a great point. So this very process, all of these features, this complex machinery, had to arise at some point by mutation, which is kind of interesting because it gives rise to this kind of circularity in the evolutionary process that we might not have anticipated before, where you have mutations that give rise to mechanisms that change what kind of mutations happen. And so, you know, some might find this circularity troubling or problematic, but I actually tend to view it as rather beautiful and an interesting new wrinkle into our

understanding of how evolution works. So what happens to plants physically when these essential genes aren't correct? They aren't repaired? So in plants, just as in humans, when essential genes are damaged by a mutation that disrupts its function, we see disease or even death or basically very harmful traits. So we see plants that just look really bad, basically. What about the opposite? Where is the most mutation happening in this plant? Right. So we found that these essential genes have low mutation rates, but when we also asked what genes have the highest mutation rates, these results were also. really interesting. We found that genes that are involved in plant adaptation and interaction with the environment are the ones with the highest mutation rates. And so our lab is also quite interested in understanding how plants adapt the climate. So this leads to some very interesting questions about

what is the role of this increase in mutation rate in these environmental response genes? Has this facilitated more rapid adaptation to climate? And when we think about climate adaptation, where environments are changing very rapidly, the introduction of new mutations in these genes could facilitate more quick adaptation than we would have otherwise expected, which is something that we haven't really thought about before, but now we're currently working on. So if they can't flee the changing climate, they adapt to it. That's exactly right. You mentioned that this plant you're studying is a weed.

If I remember correctly, it's not like a mustard plant, something like that? That's right. It's in the mustard family, so you can even eat it. You can eat it in a salad if you want. It might be a little spicy. But yeah, it's in the mustards, and it's been one of the most well-studied model systems in plant research and genetics for quite a while. So imagine it's kind of like the way we think about the fruit fly as a model system for

animal genetics or a lab rat. This is the lab rat of plants, basically. But it also grows in nature. Yeah, and it does very well in nature, right? Could the higher mutation rate in that part of the genome be related to that? That's right. It's been successful across much of the world. We can find it in Europe, Africa, North America, and it's spread.

And one question is, has this interesting pattern of mutation bias? Has this played some role in helping it adapt to new environments in a way that it wouldn't have otherwise? So this is something we're quite interested in. Yeah. So how does this research upset our entire theory? of evolution is my eighth grade teacher have to change something? You know, I don't think that it upsets our entire theory of evolution because we actually think

that these very processes are themselves the product of natural selection, that they evolve because they provide this benefit. I think that it adds an interesting wrinkle to the evolutionary story. I think that it means we're going to have to say something more complicated about mutation when we teach students, I think saying mutations are random and sort of period, end of story is a overly simplified way of thinking about mutation. And a model and theory of evolution that includes these non-random mutational processes, I think is a very interesting and elegant new way of understanding evolution with new dimensions. You know, I remember when one of the big surprises of the Human Genome Project was finding these huge regions of the genome,

that we used to call junk DNA or silent, they didn't seem to code for anything. Now we discovered that there was some use for them. Is there anything about this mutation bias that might help us get closer to understanding that particular mystery? That's an interesting question. So in this sense, you know, what we're finding is that this area of the genome that may have been thought of as junk DNA at some point, these regions that don't code for proteins, for example, that these have an elevated mutation rate. And one interesting implication of this, or one interesting question that arises from this is, does that increase in mutation rate in this so-called junk DNA mean that this type of region of the genome is contributing more to adaptation because it is a

place where there's novel genetic variation being generated more often? So I think it definitely adds an interesting element to that idea. Well, you give the genome more flexibility if you give it a place where it can mutate. Exactly. I mean, mutations are the ultimate source of all genetic variation. It's necessary for adaptation and evolution. So there has to be mutation, otherwise organisms couldn't evolve. So there needs to be somewhere where mutations are allowed to happen. We might think of it. And if not, then there wouldn't be evolution. So where those places are that mutate more often might be hotspots for adaptation. This is Science Friday from WNYC Studios. In case you just joined us, we're talking to

Dr. Gray Monroe about evidence that in evolution, mutation may not be random. Now, I know you're a plant researcher. You spend a lot of time there in the laboratory with plants, but you must be thinking about it, whether you're having a beer with your colleagues, about whether the same thing is going on in animals. Absolutely. Right? Where DNA mutates less and more important regions and vice versa? Absolutely. Of course. You can't help but think, is this something that's going on inside of our own bodies. And, you know, I'm not a human geneticist, but I've been really excited to see what's going on in some of the work, especially in the realm of cancer genomics and looking at the discoveries

that are being made about where mutations happen in human cells. And what we find is that there's actually similar patterns. So there's been a lot of really exciting work that's come out recently that shows that mutation rates can also be lower inside of genes in humans as well. And this obviously has interesting implications for human health and cancer. However, I want to point out, I think, we actually hypothesized that there's probably differences between humans and plants as well. And this is because if we go back to those, this idea of these histones that the DNA are wrapped around, we know that animals and plants have a different sort of language of how these histones are modified by chemical marks. And because the histone chemical mark language is different between animals and plants,

we suspect that the underlying mechanisms that explain why they both might have these interesting mutation biopies, these might actually be slightly different. We talked a little bit about how plants may be adapting to climate change, and I know you spend a lot of time researching how plants, especially crops, might be better adapted to drought conditions, especially farmers will have to feed people in the face of climate change, more extreme weather and so on. If this is how evolution is actually working,

what practically might change about research like yours? Yeah, we're quite interested in how we can also generate crops that are adapted for new and changing and stressful climates for plants. And one of the ways to do this is with breeding. So breeding is basically a applied science of evolution and genetics, where we use the principles of evolution and genetics to improve crops that we want to have higher nutrition or better stress tolerance. And so because it's essentially breeding is a genetic and evolutionary science, it relies on an accurate theory of evolution and genetics for it to be effective. And so this means that if we're assuming that mutations are random, if this is a core assumption of our theory, then we might not be doing as good a job as we could be otherwise. So it could obscure our ability to discover genes that are useful for accelerated breeding. And it could even mean that there are limitations to the type of genetic variation that are available.

for breeding that we otherwise wouldn't be aware of. And so having a sense of the extent of this mutation bias in crop species is also really important for developing better breeding systems, we think. I think that's a good place to end it right there. I'm afraid we have to make like a plant and leave it there. You've heard so many bad plant dad jokes, I'm sure. Thank you so much, Dr. Monroe for joining us. Thank you so much for having me. Dr. Gray Monroe, assistant professor of plant genomics at the University of California in Davis. And that's about all the time we have for now. In case you missed any part of this program, or you would like to hear it again. Yes, subscribe to our podcasts or ask your smart speaker to play Science Friday. And on the SciFRI Vox Pop app, we'd like to hear from you.

Tell us what's on your mind. Send us a voice memo. Ask a question. Way in on topics you'd like us to cover. That's on the SciFRI Vox Pop app wherever you get your apps. Have a great weekend. We'll see you next week. I'm Ira Flato.