The Big Leap: cellular evolution

Have you ever wondered how evolution operates at a cellular level? Dr. Biology has a conversation with evolutionary biologist William Ratcliff in an episode that investigates the process of how single-cell mutations can make the leap to coordinated groups of cells and ultimately to complex multicellular organisms. And we are learning all of this from a simple selection experiment involving yeast. Listen in and learn more about this long-running experiment that is giving us an idea of how single cells made the leap to multicell organisms.

Visit: Ratcliff Lab
Experiment: Snowflake yeast kit

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Chapters

• 0:00 Introduction
• 1:36 Life a few billion years ago.
• 3:28 Basic cell parts.
• 6:00 How cells do work. Cellular energy
• 8:27 How long does it take to make the leap to multicellular life?
• 11:31 Evolution of Multicellularity in Yeast
• 11:31 What is your experimental organism?
• 12:36 Yeast cell evolution.
• 15:58 A weighty matter.
• 20:01 Cell shape change
• 20:55 How to solve for the size problem.
• 22:42 Back to the genetic changes in the cells.
• 22:48 Evolution of Multicellularity and Cell Specialization
• 27:29 What do you hope to see in six year?
• 29:04 Three questions
• 29:12 When did you know you wanted to be a scientist?
• 31:16 What would you be if you were not a biologist?
• 33:14 What advice do you have for future scientists?
• 35:41 Sign-off - Learn more

Transcript

Dr. Biology:

00:00

 This is Ask A Biologist, a program about the living world, and I'm Dr Biology. For our show today we're going to do some time traveling, or at least use our minds to travel back not thousands, not millions, but billions of years. Back, to when life was just beginning on Earth and there were some single-cell forms of life, but nothing more. 

00:21

It's an interesting time, and one that scientists are exploring in their own laboratories today, with a series of experiments where they're learning how single cells evolve over time and see how cells might have made their big leap from a single-cell to a multi-cell organism. One of those scientists is William Radcliffe, an evolutionary biologist and also an astrobiologist. He's an associate professor at Georgia Institute of Technology. He's here at ASU giving a talk titled How to Make Multicellular Life from Scratch a 5,000 generation (and counting) directed evolution experiment. Today we're getting a snapshot of Will's work, as well as an idea of what Earth might have been like a few billion years ago. Welcome, Will, and thank you for taking time to sit down and talk about this simple task of evolving from a single cell to a multi-cell organism and then complex forms of life like we see today.  

Will:

01:23

Thank you, Dr. Biology. It's a pleasure to be here and I'll just say that any step that appears to be complex when you break it down into enough small steps, each single one, can be quite simple but very important ones. I guess that's right. 

Dr. Biology:

01:36

Okay, let's do what we talked about. Let's go back a few billion years and describe what Earth was like, and I'm going to give you a little jump start. 

Will:

01:48

Sure.

Dr. Biology:

01:46

We're going to already have single-cell organisms. 

Will:

01:49

So, going back to Earth a couple billion years ago is like walking into an alien planet. The evolution of multicellular life so we're talking organisms that are big enough that you can see them with the naked eye and have complex features that single cells don't have has fundamentally transformed life on our planet. Let me give you an example. So, close your eyes and think of a pristine natural forest. Right, there's light filtering through the trees. It's dancing on your face. You hear buzzing of insects maybe they're chirping of birds. Get rid of the trees. Those are multi-cellular organisms. You hear a rain of insects as they fall down. A flapping of birds, maybe a thud as a monkey falls onto the forest floor. Sorry, monkey, those are all multi-cellular animals. 

02:36

Get rid of those. What's left? Probably a bunch of mushrooms, Likely toxic. Don't eat those. Let's get rid of them. And we also have to get rid of the lichen. What are we left with on Earth? Not much. In the oceans you have some seaweeds, we can get rid of those. But my point is, if you get rid of multi-cellular organisms, life as we know it changes, Both because the organisms themselves are much more complex than their single-cell ancestors and we don't have that available to us anymore, but also because multi-cellular life has created its own ecosystems. In fact, they're so familiar to us that we call them by the name of the dominant multi-cellular organism. A forest, a grassland, a coral reef, those are the names of the multi-cellular organism that has created that niche. And in the absence of multi-cellularity, we don't have those environments either. 

Dr. Biology

03:23

Let's talk a little bit about this single cell. There are some parts.

Will:

03:26

That's right. 

Dr. Biology

03:28

So, let's talk about some of the parts that we already have. Because that was a lot of work, just as you said, maybe a lot of little steps that were simple, but what a billion and a half years. 

Will:

03:41

To go from the origin of Earth to the origin of life. 

03:44

That's a time that we have trouble pinning down, and part of that is that we just don't have really good evidence. We don't have rocks that go back past three and a half billion years, and so what we see is this sort of sudden emergence of microfossils that look like cells, and we can actually tell that they have carbon in it that came through life pathways, because carbon that came from the air and went into cells gets treated a little bit differently than carbon that's just messed around with by normal non-living chemistry. So, we're pretty sure that by three and a half billion years ago we already had cells that pretty much are the same as modern bacteria. 

Dr. Biology:

04:18

Okay, so I know this is one of those things that also because we don't really have any fossil evidence, but what were the steps, do you think, to making that first single cell? 

Will:

04:35

Yeah, in fact, these are some of the biggest steps in biology. You need some way of encoding information and having the sort of instruction manual for a cell. So that's a genome. You may have heard that word. There's DNA and that's the chemical which stores information, and you need some way of taking that information and reading it out and using it. And so, there's this thing that happens where you'd make a copy of a gene and that copy then gets turned into a protein, and the protein is sort of like the functional building block made of sticky Legos that goes around inside the cell and makes things happen. And so, you need some way of having DNA, copies of it, that can go off and do stuff, and that's not a trivial thing to sort of put together. 

05:15

It turns out that all living things, from bacteria to plants to humans, we all actually share the same exact genetic code, which in some ways is like a language. It's a sort of arbitrary way of taking chemical information like letters and turning them into words that, combined together into sentences, make biological sense and can put together functional building block proteins that can go and do specific tasks inside the cell. And the fact that all living things share the exact same, with just a few tiny modifications. Genetic code is one of these just gold-standard pieces of evidence that all life on earth shares a common ancestor. It all came from the same source. 

Dr. Biology:

05:57

Now, when you're talking about these letters and genes, we're talking about DNA or deoxyribonucleic acid and the nucleotides that it's made from. Just so everybody knows, there's adenine A, cytosine C, guanine G, and thymine T. So, we have our instructions, but how do cells get work done? They must also need some energy. 

Will:

06:25

Yeah, life fits into the niches where there are energetic gradients and dissipates that energy itself. Life is a catalyst to dissipate energy and by doing the dissipation of the energy it is able to sort of do biological work. Let me give you an example here. So, we have a planet which has a liquid water surface, we have oceans, and we have a sun, and that sun is actually a gigantic battery. It's throwing all these photons at the planet. Now let's say that we don't have photosynthetic life yet. We don't have life that can actually use that life for energy directly. We still have water molecules, and those water molecules can be blasted apart by ultraviolet radiation. 

07:02

If you know water molecules, H2O right, you knock it apart into H2 and O, and the hydrogen, the H2, it's so small, it's the smallest element in the periodic table and it's very light and it can actually escape out into space and as a result, you end up getting a relatively small but meaningful amount of oxygen. 

07:21

Now that oxygen it wants to do chemical work. Oxygen can oxidize and what you end up having in the planet is a core. We haven't talked about this yet, but the center of the planet is made out of metal, iron, and if you know iron, you know what happens when it gets wet in the presence of oxygen it rusts. That actually releases a huge amount of energy. And so,  what you have is a planet that acts like a battery, because you have in the oceans hydrothermal vents. They're like underwater volcanoes, a connection between the core and the surface, and you have rusting of that core, iron engaging with the oxygen of the atmosphere and, as a result, you have a flow of electrons from the center of the planet up through the surface and out into space, and that continues for essentially billions of years and provides a modest but steady source of energy that, if you're a little precellular critter living at that interface, in these hydrothermal vents, there's just a steady source of energy that's pretty similar to what you see inside one of your cells. 

Dr. Biology:

08:21

Let's step back. We've got energy, we've got parts of our cell, we built our cell, but it's just a single cell.

Will:

08:25

That's right. 

Dr. Biology:

08:27

How long does it take and what does it take to make that leap to multicellular life? 

Will:

08:40

So, that’s a good question, and it turns out that it's not something which has happened just once or twice. Multicellularity this way in which you build a body for multiple cells and that body begins to gain its own adaptations and traits that make it capable of doing things that single cells can't do anymore that transition has happened many times in the history of life, at least 50 times separately. The very oldest ones go back almost to the origin of cellular life itself. Cyanobacteria pond scum, if you will, became multicellular about 3 billion years ago and then, much more recently, you've had things like the brown algae, a big clade of seaweed that you'll see if you go to the beach and you find these big brown kelp washing up. Those are some of the new kids on the block. They've only evolved multicellularity roughly 200 million years ago. 

Dr. Biology:

09:27

Okay, it took millions of years to go from a single cell to a multicell organism. You’re running an experiment with single cells to see what happens as they keep going through this process. How are you going to compress billions of years? 

Will:

09:44

Yeah, great question. So, I think there's a bit of a bias towards looking back in time and assuming that just because something arose a long time ago, it necessarily took a very long time to get there. So, we have this thing called the Cambrian explosion and you can't see me, but I'm doing air quotes right now, because whenever a geologist tells you something happened fast, you need to like critically think about what they think fast is. But if you look in the rock record, you'll see a world in which there aren't really that many large animal-like things. Roughly 530 million years ago, and within the span of 5, 10, 15 million years, the oceans are just populated by all of these very cool looking animals and, geological terms, 10 million years is so fast. It's an explosion. In human terms, that's still pretty slow. 

10:31

But that being said, I don't think that we are setting our sites quite as high as building something as complicated as a fish or something with a spinal cord or something with eyes. That's a very high bar and indeed those types of traits probably do take quite a long time to evolve. What we're looking at are the earliest steps in going from a single-celled organism to a small group of cells that stay together to form sort of a clumpy thing. And then, over generations, we're going to watch the cells in that clumpy thing begin to take on different roles and different behaviors and watch the groups themselves begin to gain multi-cellular adaptations, which means traits of the group which don't really have a single cell analog. They're different from the cells in the same way that your ability to run faster, jump high, depends on the muscles in your legs, but it's different from the shape or strength of a muscle. It's an emergent property of having these cells interact together. And so, we're watching those same dynamics play out, but on a much smaller, much simpler scale. 

Dr. Biology:

11:31

So, what is your favorite organism? 

Will:

11:36

Snowflake  yeast yes, no, no, no. My children, my children. 

Dr. Biology:

11:38

Yes, so here we are working with yeast. Some people probably use yeast on a regular day. 

Will:

11:46

I think many of us do. You enjoy bread, beer, wine or other fermented foods. Yeast are a critical part of that and the yeast that we use certainly are formerly domesticated by humans because of their ability to make alcohol and to leaven doughs. 

Dr. Biology:

12:01

Yes, and I have to say I do love my bread. Now, as far as the experiment you're, let's see here 5000 generations and counting. 

Will:

12:08

We're actually around 8,000 generations by now. 

Dr. Biology:

12:12

8,000? 

Will:

12:13

The title to my talk says 5,000, and that's the data that I'm showing. But we're actually racing ahead of that in terms of our experiments. But it takes a long time to analyze the data that we're collecting, and so we tend to sort of get a nice round number, stop there and spend years analyzing the data that got up to that point, but the experiment continues every single day. 

Dr. Biology:

12:36

Will, let's talk about some of the evolution that's going on with your yeast. 

Will:

12:40

Right. The first step that I'll tell you about is we use this system to understand how a group of cells can be something which is able to undergo the process of Darwinian evolution, which is actually something we can't take for granted. We know that cells can because cells reproduce. That's a critical step. They get mutations which can change their traits. It can make them grow faster or do something which makes them survive better, and they can pass those traits on to their offspring and, as a result, those traits can persist in the population, and that's what we call evolution. But the evolution of multicellularity requires those properties reproduction, heredity to be properties of the group, and that's something which, in organisms like you, me and plants, is very different from what their single-celled ancestors would have done. And so there's this sort of gulf. How does a group of cells which doesn't already have a mechanism of coordinating reproduction, a mechanism of coordinating development which can be passed on to offspring. How do they nonetheless gain the ability to evolve at the group level? So, we spent many years decoding this with our yeast model system, and it turns out that they get the ability to evolve as a group totally for free. 

13:47

We thought you had to get it through biological solutions, but you get it totally for free as a side effect of physics. So, imagine if you have a cell and it starts making offspring and those offspring stick to it and you're getting a clump. It's sort of like you're building a little tree on your desk with ping pong balls right, and every time the ping pong ball divides you add another one. Pretty soon you have this cool little tree like a group and it's going to get densely packed on the inside. And if you keep trying to jam ping pong balls in there, pretty soon you're going to break it. In our yeast that's exactly what happens. The cells divide and they eventually break. And when they break they break off a little branch. And that little branch it's a baby snowflake. It looks like it's parents, it has the same shape, it's just a lot smaller and it's no longer very densely packed. So, it grows back up to its parent's size and it begins doing the same thing, breaking, growing, breaking, growing. And if I take one snowflake, put it into a test tube and come back the next day, there will be a million and they all look just the same as their parent. So, we have a life cycle of reproduction. 

14:48

We don't yet have heritability, like how can we get new multicellular traits? We don't have any development yet. 

14:56

Turns out that physics also lends us a helping hand here, because if you can get mutations at the single-cell level which change the behavior of the cells. You change their shape. You change the angle at which they bud. You change the strength of a cell-cell connection. Those change the way that the group as a whole looks and behaves. It's not directed, it's not controlled in the way that development in an organism like us is controlled by these very sophisticated processes in your cell. It's all happening in a way that's completely emergent, that is, it's not directed, it just happens in the way that if you pile sand up on a table, eventually it's going to spill down, right, you're not telling it to, it just happens because of physics. So, it turns out that we can get multicellular traits arising as an emergent property and natural selection sees them and can act upon them. And we get this process of open-ended multicellular adaptation where our groups are essentially getting better and better at growing as a multicellular organism. Because through this process of natural selection acting on emergent physical properties of groups. 

Dr. Biology:

15:58

And by doing that when they get bigger, they get heavier. 

Will:

16:00

They do. They do yes.

Dr. Biology:

16:01

Which is part of the key. 

Will:

16:02

That's part of the key. So, the way we do our selection experiment is very simple, because I've learned the hard way that if you make a fancy selection experiment you're going to mess it up. You have to remember we have to do our selection on our yeast every single day, seven days a week, 365 days a year. Yeast don't know that Christmas exists, they don't take holidays, and so sometimes you're tired, sometimes you've been out late celebrating an academic achievement, and maybe you've had a few too many yeast drinks that leave you feeling pretty bad in the morning. And if you have a complicated experiment, you're going to mess it up. So, our experiment is very simple. We take our yeast, and they grow in an incubator, where the incubator is spinning, and at this point all that matters is how quickly they grow and that they make a little multicellular babies. Then, at the end of the day, they go through a race to the bottom of the test tube and the biggest, fastest-sinking ones, they win the race and they go on to the next day's media and everything else is poured down the drain. Sorry for them, but that's the end of the road for them. 

17:01

And so, we're selecting on bigger, tougher, multicellular groups. We're also selecting on the ability to deal with the fact that once you get big, diffusion begins to be a problem. There's a lot of food in the media outside, but the inside doesn't have it right. The inside of that group is starving. You have a circulatory system that's solved the problem of diffusion in your body. Our yeast don't have that, but we want to incentivize them to come up with some way of solving these problems. 

17:28

And so, we're pushing on size. We're making them try and figure out ways to get physically stronger, to get bigger, and we're also making them deal with the fact that they're growing slower. And maybe they can figure out ways around that, and they do. They figured out things that took human physicists hundreds of years and they figured out in a matter of months. One of the things that they do is that they evolve to get about 20,000 times bigger than their ancestor. 

Dr. Biology:

17:50

20,000 times, 

Will:

17:51

20,000 times bigger. They start out forming groups of about 100 cells and after 600 rounds of this selection, which is about 3,000 generations for our yeast, they are now roughly half a million cells per group Way bigger and they're also correspondingly much, much stronger as a material. The technical term for this is toughness. It turns out that toughness in material science is how much energy it takes to break something but taking its size out of the equation. So, the toughness of a toothpick and a 2x4 are the same. 2x4s just take more energy to break because there's more material there. Our things become 10,000 times more tough as a material. In fact, they go from being 100 times weaker than gelatin to being as strong and tough as wood, and they do it through some really cool physics. 

Dr. Biology:

18:44

Alright, so now we've talked about shape, we've talked about oh, size, how do you get that much bigger? 

Will:

18:54

Yeah, so snowflake yeast start out growing like a tree with cells at branch. And like a tree, if you break a cell-cell bond like cutting a branch off that tree that branch just falls right off. But to get stronger and bigger they need to figure out some way that they're not one cell fracture, away from breaking the whole group. What happens is they actually make their cell-cell connections stronger and their cells longer, and they can actually stay together long enough that the cells begin to wrap around one another like vines. And when they do that, the whole group becomes like a group of Velcro, right In the physical sense entangled. And now to break a branch off, you're not breaking one bond. You have to break the bonds of every cell to every other cell and you're ripping them all apart and you have to break tens of thousands of cellular bonds and that makes the whole thing tens of thousands of times stronger and larger. 

Dr. Biology:

19:48

Right, because you have to remember that you've got them in these incubators that are constantly moving. They're shaking right. 

Will:

19:53

That's right. 

Dr. Biology:

Host

19:53

If you can't figure that out, you're not going to be able to grow bigger and stronger. There is a fundamental limit.

Will:

19:58

Exactly, there is a complete cap in the absence of that. 

Dr. Biology:

20:01

So, the cells, then these cool newer cells that have figured this out. They're longer, they're elongated and they're twisted. Ahh.

Will:

20:08

Yep. They actually stay fairly straight. But what happens is the group stays together long enough that the cell makes sort of like a horseshoe shape. When it does that, it grows over another branch, and if every branch is making a horseshoe shape around one another, you can think of like a Velcro when you're a sneaker and the cells are kind of doing that thing where they're wrapped around one another, and it makes them as strong as a little ball of wood. 

Dr. Biology:

20:33

Huh yeah, very cool. 

Will:

20:34

Yeah. 

Dr. Biology:

20:35

So, we've grown but you also mentioned diffusion as being a problem. 

Will:

20:40

Oh yes, oh yes. 

Dr. Biology:

Host

20:42

Just getting big in any shape isn't going to work. 

Will:

20:46

It could work, but it's not ideal. Yeah, yeah, yeah. 

Dr. Biology:

Host

20:49

Because, how do you get that food, the media, if it's a big ball. 

Will:

20:53

And that's what they are. They're a big ball, exactly. 

Dr. Biology:

20:55

So how do you change your shape to still be big? But 

Will:

21:57

So, there's two general solutions here. You can either change your shape so that every cell is near the surface, which is something like what a fern leaf would look like. Right, it's big, it's flat and there's a lot of surface area there. Everything's in close contact with the environment. The other way to do it is something like what an animal would do, which is to move the environment through you. If you move the environment through you, then you don't have this problem of diffusion limitation. 

21:25

This was very surprising to us, and this paper everything else I've told you about is published research and you can read about it on the internet. You can go to my website, Ratcliff Lab, but this is actually unpublished work, but I'll tell you about it anyway, because we're going to be submitting it soon and we've talked about it at conferences and I'm talking about it tomorrow. So, it turns out that have you ever seen a sea sponge? Sea sponge looks sort of like a peanut and the cells inside a sea sponge have little like lassos and they're moving the water through their bodies and they're filtering out bacteria. If you looked at a sea sponge from the side, it would be shooting water out the top like a little volcano. 

22:03

It turns out that our yeast they don't have any way of directly moving water. They don't have these things called the flagellum, which acts like a little lasso to move water, and yet when we look at them, they are flowing water through their bodies extremely quickly, like faster than many organisms with these specialized water-moving devices, and, as a result, the cells on the inside have perfect access to food and don't starve at all. We can actually grow them under controlled conditions and get them to be the size of a marble, and they're still growing just as fast, as if they were the size of a period on the page. 

Dr. Biology:

22:40

Wow. 

Will:

22:41

Yeah, 

Dr. Biology:

22:42

We've talked about and you've described the structure changes and what's been happening. What about those genes? 

Will:

22:45

Ah, good question. Are we getting cells specializing in dividing labor, which is one of these hallmarks of multicellularity? And, to be honest, I think it's one of the things that makes multicellularity exciting. If multicellularity was just big blobs of cells that were all the same as one another, I don't think we'd care about it. That would be more along the lines of a really impressive pond scum, which is cool. Don’t get me wrong. That's cool, but it's not the same as an organism with parts that work together towards a group-level goal. That's something that the single cells couldn't have done, and that's the superpower of multicellularity, and so this is also work that's in progress. This is unpublished research. 

23:28

We've used a very cool technique called single-celled RNA sequencing. What we can do is we can look at a readout of what genes are being turned on in individual cells, and we can do this in a pretty high throughput way. So, in the ancestor line, in a 1,000-generation line, in a 2,000-generation line, we do this all the way up to 5,000 generations. We take the organisms, we break them down into single cells and we do a little readout of what genes those cells are expressing and turning on. In the ancestor they're all the same, as would be expected, because it's basically only one generation away from being a single-celled organism, it's just forming a group, and by a thousand generations, we actually have two distinct cell types. We have the normal ancestor-like cells, and we have a cell type that looks quite different on a graph of gene expression. It's in its own distinct place and those cells are mostly over-expressing cell wall material. So, we have some cells that are hitting the gym. They're getting really strong, but it's only a subset. Right 10, 15% of the cells are doing this, and if we stain cell walls we actually see that they're not randomly localized throughout the groups. These are the oldest cells in the groups, the cells that have the biggest number of branches coming off of them, the ones that are actually under a lot of physical strain, and when our groups break, that's where they tend to break. So, it seems like there may be a bit of a sort of simple intelligent strengthening of critical cells which allows them to get stronger as an organism and that cell type persists all the way up to 5,000 generations. Around 3,000 generations we get a third cell type and actually, there's something interesting happening here. 

25:05

Between 2,000 and 3,000 generations is when our yeast become really big. It's when they go from being a few hundred cells to being a few hundred thousand cells, right, much, much bigger. And it turns out that getting really big comes with a serious cost. It's not a growth rate cost, like we discussed earlier because they're moving fluid through their bodies and they're not really growth-limited. But there's another cost in our experiment, which is that our groups have to reproduce and make offspring, because every day we only transfer about 1 in 32 of the groups that were in our population as a whole, and if a group just grows indefinitely and doesn't make babies, then it just gets thrown away eventually and it and all of its cells are gone. So, in fact, every day if a group wants to persist it has to have at least 32 offspring. Otherwise, every day there's a smaller and smaller number of them, and that's a very important thing in our experiment. And to get strong and build big groups, they do this by sacrificing the way that they reproduced, which is this physical strain building up and breaking branches. 

26:11

When they get so strong that they don't break branches anymore, that's kind of a problem. They win in the race to the bottom of the test tube, but they lose in that they don't make babies very well anymore and it looks like this third cell type is something where cells actually commit suicide. About 20 to 25% of the cells in the group turn on genes that cause them to die and this starts to break little, tiny branches that are not part of the strong interior, entangled part of the cluster which those things can't really leave anymore, but cells that are on the edge now separate, and so you have these groups now that are turning on all these cell death genes which cause cells to die. Instead of breaking off giant chunks of maybe 10,000 cells to reproduce, they are shedding two, three, four, five cell babies and shedding many, many of them, and that's the way in which they engineer reproduction. So, they're kind of getting a new life cycle by using a simple form of cellular differentiation. 

Dr. Biology:

27:07

Very cool. 

Will:

27:08

I love that. 

Dr. Biology:

Host

27:09

Yes. 

Will:

27:09

Very cool. I will say that one. We have yet to functionally validate that result, so that's a hypothesis. This is what we think is happening. It sure seems that way, but I want to just say that it's something which we need to do a little bit more research before I'm 100% convinced of that result. 

Dr. Biology:

27:25

Now, this is part of the scientific process. 

Will:

27:27

Exactly that's how science works. 

Dr. Biology:

27:29

Okay, so where do you think you're going to be? And let's go ahead six years. 

Will:

27:36

Yeah, yeah, yeah. 

Dr. Biology:

27:38

And you'll be at what 16,000 generations in the experiment. 

Will:

27:42

Probably yeah. 

Dr. Biology:

27:44

What do you want to see? 

Will:

27:45

I'd love to see something more complex than just a blob of cells. I'd like to see multi-cellular development, coordinated growth, getting a shape that is a little more interesting than just something which looks like an asteroid, which is kind of what they look like. 

27:57

When I'm looking at it under microscope, they look kind of like asteroids and we're actually getting tantalizing evidence. This is just the very beginnings, but if we let them grow, where they have these strong flows, where they're actually pushing water through their bodies, they actually begin to grow in a different way and form a hole in the center and looks sort of like a doughnut, which is actually a very interesting shape in developmental biology. Going from a clump to a doughnut is actually a pretty big deal, 

Dr. Biology:

28:22

Yeah it'd be a huge deal. 

Will:

28:24

Yeah, I'm interested in understanding better the way in which cell specialization evolves in different parallel-evolving populations. Right now we've only looked at one population, but we have five that are evolving in parallel. They have the same starting point but independent evolutionary trajectory. 

Dr. Biology:

28:43

Let's see what happens. 

Will:

28:44

Right, yeah, is it the same thing? Does it do? 

Dr. Biology:

28:46

Does it do exactly the same thing. 

Will:

28:47

Is it different? 

Dr. Biology:

28:48

There's all sorts of possibilities there Exactly. So, what we'll do is we'll have to have you back in six more years. 

Will:

28:55

Sounds great. I'm going to do this until I retire or die, so I have plenty of time. 

Dr. Biology:

29:00

All right. Well, we'll go for retirement. 

Will:

29:02

Sounds good, all right. 

Dr. Biology:

29:04

Well before my scientists get to leave. Ask A biologist. I always ask three questions. Right, so are you ready? 

Will:

29:11

Sure. 

Dr. Biology:

29:12

Okay, when did you first know you wanted to be a scientist? Or, in this case, did you know you wanted to be an evolutionary biologist, slash astrobiologist? What happened? 

Will:

29:26

So, I knew I wanted to be a scientist when I was a kid, because I just loved learning about science. Like I couldn't get enough, we had a once-a-week science teacher that would come and tell us about science in my grade school and I would just like be so excited on those days. I had home kits and books and I would do those and honestly, I loved spending time in nature and just looking at organisms and if you think about it, all of the drama that you see that humans have with respect to the way that we interact, the highs of success, the lows of failure, those things happen, but on an even greater scale in living systems where the stakes are often life or death. So, as soon as you start to sort of notice the world around you, you realize that it's just this never-ending fascinating tapestry of interactions. And I think I knew I wanted to be a biologist when I started to connect those interactions and understanding how living things fit together in their environment with the way that they got there in the first place, and thinking about the history and how those things in fact got to be the way they are. 

30:27

How did that beetle get those jaws and become a predator, ripping apart other insects, while it's close relative is a pollinator and completely, completely gentle. You know, those are great questions. So, I think I knew at a young age, but I don't think I knew I wanted to be a scientist until the end of college when I was like what am I going to do? 

Dr. Biology:

30:45

You just didn't know you wanted to be a scientist or didn't know. You wanted to be a biologist. 

Will:

30:49

I didn't know. I wanted to be a research biologist. I did a plant biology undergraduate degree again for my love of nature, but I didn't really know what I wanted to do after college and I sort of lucked into our research lab, my favorite professor. I went and talked to him like what should I do? And he was like I just got a grant, why don't you start working in my lab? Okay, and then the rest was sort of history. But it wasn't something which I was planning to do for a long time, even though the interest was always there. 

Dr. Biology:

31:16

Well, with all your enthusiasm, I really hate to introduce this next question because I'm going to take it all away. 

Will:

31:21

Oh no. 

Dr. Biology:

31:23

Now, this is just a thought question, right? If I took this away from you and I'm going? To take away teaching, because every scientist I've had on loves doing the teaching. So, you're not going to be a scientist, you're not going to be teaching. What would you be or what would you do If you could do anything? I'm going to give you some abilities that you may not have. 

Will:

31:46

Oh, that's such a cool question. Okay, it's a toss-up between professional beekeeper. I'm a hobby beekeeper. In my backyard, up until this last year, which has been sort of a rough year for me, I had about 30 bee colonies and I make about 1000 pounds of honey a year and I really love bees. They're just such fun organisms to spend time with and they have such alien cognition and I just love seeing the world through their eyes. It's a very fun thing to just immerse yourself in a bee colony Not literally, that would be painful. 

32:21

So yeah, I've thought about it would be fun to scale that up, although I think what I've learned with scaling as a scientist is that you become a manager and not the actual actor, and so I probably wouldn't be able to spend time with bees if I was actually a professional beekeeper. But if that wasn't the case, I would, if I could have any skills. And I'm not a scientist, okay, I would be a - this is going to sound weird, but I think I might want to be an engineer developing frontier artificial intelligence technology. Because I think that's really fun to think about and I like to play around with it as a hobby. I'm not sure that it's the right thing for society, but at a purely intellectual curiosity level, I think it's really fun and interesting to play with. 

Dr. Biology:

33:06

Right, I mean, it's something we need to confront. 

Will:

33:10

It's coming, it's here. The genie's out of the bottle. 

Dr. Biology:

33:14

All right. Last question, what advice would you have for a young scientist, or perhaps someone who's doing something that's not in the sciences but always loves science and they want to get into a science career? 

Will:

33:30

I think my advice would be to figure out a way to start a research project. It could be a hobby project; it could be something you do at home. Better if you have someone who understands you know that field, that can act as a mentor. But doing science and learning about science, the way that we teach science, especially the undergraduate or lower levels it's very different from the kind of hands-on experience that you get if you actually do a project. Because a lot of doing science is confronting unknown, is learning things on the fly, is dealing with failure, is iterating. It's a very different experience than getting the distilled version of thousands of hours of work from hundreds of people and saying here is the answer to this question. 

Dr. Biology:

34:16

Right, because there is no book on the shelf with all the answers. 

Will:

34:21

No, the vast majority of scientific questions are yet to be even posed, and so there is a huge amount of exciting work to be done out there, and I think for me it's really fun and exciting to be able to actually be on the frontier of science and asking questions and, you know, doing that sort of like work that doesn't already have an answer. 

34:40

I think there's a real joy to that, and so, for those who are interested in a scientific career, if you have the opportunity, whether it's through, if you're an undergraduate student working in a lab, if you're just a member of the community, I'm sure there are all sorts of opportunities to get involved. A lot of clubs, like beekeeping clubs, will have scientists that are affiliated and get a certificate and do a project. You could be a master gardener, I mean, there's a lot of ways to do this, and I think when you're doing science, when you're asking questions, posing hypotheses, and testing those hypotheses with a controlled experiment or other means of testing a hypothesis, you are a scientist, even if you don't have formal training. You are a scientist if you do science. 

Dr. Biology:

35:18

Absolutely, and along those lines. Do you still have your snowflake yeast kits? I do yes. All right, well, we'll be sure to put the link in so someone can go if they want to. They can play with not necessarily your children, but 

Will:

35:28

My yeast children. 

Dr. Biology:

35:30

Your yeast children. 

Dr. Biology:

35:37

Will, thank you so much for being on Ask a Biologist. 

Will:

35:39

It's been a pleasure. Thanks for having me. 

Dr. Biology:

35:41

You have been listening to Ask A Biologist, and my guest has been William Radcliffe, an evolutionary biologist and also an astrobiologist. He's currently an associate professor at the Georgia Institute of Technology. 

And I suspect some of you have more questions that have cropped up during this episode that we may not have answered, so we'll be sure to include some links in the show, including one to Will's lab website so that you can learn more about his work and explore the world of yeast. That's also where we'll put the link to get the yeast kit. The Ask A Biologist podcast is produced on the campus of Arizona State University and is recorded in the Grassroots Studio housed in the School of Life Sciences, which is an academic unit of The College of Liberal Arts and Sciences. 

And as a reminder, even though our program is not broadcast live, you can still send us your questions about biology using our companion website. The address is askabiologist.asu.edu, or you can just use your favorite search engine and enter the words Ask A Biologist. As always, I'm Dr Biology and I hope you're staying safe and healthy.