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In the beginning...
Well, scientists aren't actually sure what happened in the beginning. Specifically, they don't know exactly how life on Earth began. Most researchers agree that it involved water, which is why last week in the first episode of our Origins series, we explored where Earth's water may have come from. But now that our watery stage is set, we've still got what might be an even bigger question.
What happened next? How did we go from having a bunch of water to having a bunch of life in that water? Some researchers have this kind of wild approach to finding out how life started. They're trying to make it themselves, to recreate life in a lab. Science writer Michael Marshall wrote a whole book about this quest, and our intrepid reporter Bird Pinkerton reached out to him to hear more about these weird, wonderful experiments.
The story Michael Marshall told me begins in the 1950s, and it starts with a Nobel Prize-winning professor named Harold Urey. He was a chemist who at that point was sort of only a few years away from retirement. And Michael says that in the final decades of his career, Harold Urey had gotten into all kinds of interesting projects, including trying to figure out what the early Earth might have looked like
after water had come about, but before we had life yet. He used what was known about the chemistry of other planets to come up with a vision of Earth billions of years ago, suggesting that it might have been this hot world with oceans and volcanoes, lightning, and lots of ammonia and methane. And from that kind of wild vision came an even wilder idea. If you could recreate that early world in a lab, kind of in miniature,
Could you answer a fundamental question about our origins? This question of how did life come about? What was the mechanism? This is where one of Harold Urey's students comes in, this guy named Stanley Miller. Miller eventually approached him and said, well, why don't we try it? Why not try to mix together some ammonia and some methane, simulate volcanoes and lightning together?
And see if anything lifelike comes out. And Yuri was initially like, God, that's a bit of a risk. You know, I mean, what if, you know, it probably won't work. But Miller kind of talked him into it. So in 1952, they started creating a tiny world.
The setup they used was like incredibly simple. They had two glass containers, one of which has water in it. Their version of the primordial ocean. And the other one has a mixture of gases. Methane, ammonia, and hydrogen. And that's meant to be the primordial atmosphere. These two glass containers were then linked by glass tubes.
And each of them was being manipulated in some way. The ocean one, the water one, is being heated gently to simulate the effect of volcanic activity. And also because it was generally assumed that the Earth was probably quite hot when it was young. And then there was an electrode in the air flask that would kind of create electric shocks every once in a while. And that was meant to simulate lightning strikes. And once they'd set up this tiny world to simulate early Earth, they...
just kind of let it do its thing for a few days. Like they did not futz around a whole bunch because as far as we know, the ancient earth did not have a bunch of lab scientists like pipetting substances in and out of the ocean or the atmosphere. But stuff started to happen. The water changed color. So it went first of all yellow and then eventually brown. So clearly some kind of chemical reactions have been going on. But at this point, they can't tell what it is. All they can see is that something has happened.
Eventually, Miller stopped the experiment, analyzed the water to figure out what new substances were in it, and what he found was evidence of an organic compound called glycine. And this was like the eureka moment of like, I can't believe I've done that. But I imagine that for people who don't have a background in organic chemistry, you're going to go, glycine? What? What is that? Glycine is an amino acid, so one of the most basic building blocks of life.
Which means that Stanley Miller had set up a super simple experiment, and on his first try, he'd shown that you could take common lifeless chemicals, mix them all together kind of randomly, and a key component needed for life would just emerge with very little intervention. This moment, this unexpected triumph of the Miller-Urey experiment,
It's inspired 70 years worth of research, research that's still ongoing. And scientists have spent many of those decades getting more building blocks of life to spring up from lifeless chemicals. So proteins and RNA and sugars and fats. But they're also trying to make the biggest leap here. Like they want, at some point, to find a way to create not just the building blocks of life, but actual life.
in a bottle or a beaker or some test tubes and flasks. If they succeed, they're hoping to get some clues about how life on Earth might have started four billion or so years ago, or potentially to learn something fundamental about life itself. Every marvelous living creature on our Earth is built of complex living cells. Living cells.
Life is made up of atoms and molecules and chemical reactions. But what makes them alive? How does this come about? What is life?
So one big hurdle here is that life is kind of awe-inspiringly, jaw-droppingly intricate. Like, most of these origin of life researchers agree that they are trying to build some version of the most basic unit of life, right, a cell. But the word basic is kind of misleading because, as Michael made clear to me, modern cells are very, very not basic.
Even the simplest bacteria have over a hundred genes and thousands of specified molecules like proteins and sugars and whatnot going on in them. All these systems within the cell intersect and are dependent upon one another.
It's this whirlwind of transcription and translation and regulation, all these systems that are so intertwined and in tune with each other that if you try to pull out any part or even change any part too dramatically... It causes, like, cascading failures in all the other ones and will probably kill the cell. So most origin of life researchers look at this dazzling interconnectedness and they think that the very first cell cannot possibly
possibly have been this complex. It sort of seemed wildly implausible that all of that just kind of sprang up out of nothing altogether. You obviously have to boil it back to something simpler. Which sounds simple, right? Like it's literally something simpler.
But this is also not all that basic because no one is completely sure what that something simpler actually looks like. If you ask any two origin of life researchers what they think the very first life looked like, you will almost certainly get different answers. Still, over the years, Michael says that a
tenuous consensus has developed about what origin of life researchers are looking for. If you would try to really boil it down, most people will agree that a living thing has to have like a small kind of short list of properties. Original basic life form property number one,
It can hold itself together, like it doesn't just fall apart. The most basic cell probably has some kind of a structure, like a membrane or a wall, something that separates it from everything around it. And by itself, that's not enough to be alive, but that's part one.
The second thing which kind of goes along with that is that it's self-sustaining. It's sort of active and it keeps going. And that means that it's going to be taking in energy from its surroundings in some way. This is basic life cell property number two. Life probably has some kind of a metabolism, a way to power all its systems.
Now we do that by like eating food and digesting it. That's not the only way, you know, some other plants take in sunlight instead. But in one way or another, it's taking in energy and using that to sustain itself. And then finally, there's basic lifestyle property number three.
it needs to be able to reproduce itself. Now, that doesn't mean we're not sort of invoking anything as complicated as sexual reproduction. It's just, it's probably just a case of simple copying. So, you know, start with one, divides into two, or sort of makes a copy of itself. So you have two and then you have four. So the most basic life form would probably have to have these three interlinking things.
be able to hold itself together and sustain itself and copy itself. You have those things all together. Either you're alive or you're doing a very good impression of it. Over the last 70 years or so, researchers have fiddled with different models of the early Earth. They're pretty sure Yuri's vision wasn't correct, so they're trying other things. And in their fiddling and testing, sort of recreating different scenarios with different chemicals, different acidities, different temperatures,
They've figured out how to assemble lots of different building blocks of life, including building blocks that have maybe one of these three properties. Like, they've been able to make lipid blobs that look a lot like cell membranes. So check off structure. Or they've gotten RNA molecules to form, which are like simplified DNA and can pass on genetic material, which is copying. Check. The problem is... All of these things are so incredibly hard to make.
This is Dr. Anna Wang. She is a research scientist at the University of New South Wales who has done work like this. And she says that getting one thing, like a cell structure, to appear in a flask of random ingredients is hard enough. But getting three things to all appear in the same flask of random ingredients, all at the same time? Right now it feels pretty much impossible. So how do you attempt the pretty much impossible? Support for Unexplainable comes from Greenlight.
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Origin of Life researchers have gotten pretty good at figuring out how to make various building blocks of life appear by mixing chemicals together that might have existed at the beginning of the Earth. But they have not figured out how to do — at least, not yet —
is to get all the building blocks of life to assemble all at the same time and come together as a quote-unquote living organism. In fact, it seems like a kind of impossible task. But a couple of research groups are toying with different variations on a kind of solution to this problem. In its most basic form, as Anna Wang described it to me, the idea is this.
Four billion years ago, maybe Earth was just the best laboratory that ever existed. In a lab, you can have lots and lots and lots of test tubes with lots of experiments running side by side. And each has slightly different conditions in it. Maybe one test tube is perfect for making membranes. Another one is really good for making RNA, that sort of simpler form of DNA. A third one has some kind of metabolic engine.
And then if you combine all those test tubes, then you have all your different building blocks of life all in one place and potentially ready to assemble. And there are a couple of different ways that you could potentially have seen this many test tube scenario on early Earth.
So one way that maybe this happened is that you had a bunch of different little shallow pools in hot springs. And so you can imagine a place like Yellowstone or Rotorua in New Zealand. We have a bunch of different shallow pools and one of them is super acidic and really, really hot. Like if you dropped...
a finger in there, you might not get your finger back. And the one next door to it is super basic and a bit cooler. So they have completely different reaction conditions. You can make totally different molecules. This is oversimplified, but you can imagine having, like, an RNA pool and a lipid pool, et cetera,
all close to each other. And all of a sudden it rains or there's some volcanic activity and those hot spring pools bubble over and they can start intermingling with each other. And that's when the magic happens. Those ingredients combine, maybe get sunny again, things dry down and get concentrated, and then you can start making what we might call a protocell. And so these are the primordial, primitive cells that were the precursors to life as we know it.
So that's one way that you could potentially achieve the impossible and get all these building blocks of life to mix. But there are other researchers exploring other potential spots for this kind of laboratory combo magic on early Earth, including researchers looking at hydrothermal vents.
So these are spots in the ocean where water descends into cracks in the earth and then kind of vents back out again, hot, full of chemicals. Those chemicals mix with the ocean, they turn into minerals, and those minerals then start to pile up where the vent comes out of the seafloor. The pile grows and grows, and then eventually it becomes a structure. It kind of goes vertically upward, and it becomes a little chimney. Lori Barge is a research scientist at NASA's Jet Propulsion Laboratory.
She does lots of work with these underwater vents in their chimneys. When you're in the natural environment, they can become huge. So these can be meters tall, sometimes tens of meters tall, like the size of a building.
Depending on the minerals it's made of, a chimney can be black or white or green or red or even a kind of calico mix of colors. And its inside is hollow, so the fluid's going through it, but there's also a lot of pores within the chimney. So the chimney looks like a sponge. It has a lot of little holes and pores within, and the conditions in one pore could be very different than the conditions in another pore.
In an early Earth scenario, the pores on the outside of the chimney might be reacting with acidic ocean water. And the pores on the inside might have different chemicals coming up into them from the vents in the water. And so similar to the shallow pools on early Earth's surface, the mix of minerals and chemicals in these pores could have potentially led to all kinds of different combinations.
It is like a pile of little test tubes. Each one is a little bit different. And this is why the chimney is so interesting because it's not just one condition. And also, of course, different vents have different chimneys. So, I mean, the conditioned space is really large.
and the pores themselves are connected to each other more or less. So you can even have, you know, in one test tube, you make one reaction and then the product of that reaction goes a little journey and goes into a different test tube. And now you have another reaction possible in a different condition in the same chimney.
In this scenario, again, you might have a few pores where the right building blocks for life, which Lori calls organics, all mix together in one place. And then the details are the mystery here. And so maybe the organics begin to become longer and bigger. Maybe a membrane forms. And then maybe a very early life form exists that is able to live off of that energy in the vent. And then eventually, eventually, it is able to generate its own energy enough to leave.
There are also other stories out there, stories that involve life growing in ice or even some parts of life coming to Earth from outer space. Different ways of making that first seemingly impossible leap to life. Each theoretical story is a set of basic assumptions about an environment that a researcher like Laurie or Anna can work from.
And then they can swap in different minerals or attempt different variations in temperature to see what happens. And right now, they are still making building blocks, these cell membranes or RNA, various proteins. But slowly, experiment by experiment by experiment, Laurie and Anna and other researchers in this field are
they're building up a base of information that could help them understand which random conditions might have needed to occur in various pools or pores and then combined in order to lead to a first potential cell. But we're nowhere near that point just yet. And so still, we're at the point where looking at all these things separately or them in pairs is great. We're still learning a lot. And one day we'll get there to look at it all together.
But here's where things get a little wild to me. Because when I started talking to everyone in this reporting, I was assuming that when researchers did create something that everyone recognized as life, that would be it, right? Like they'd have solved the riddle of our origins. They'd be able to finally say, okay, in the beginning, there were some ponds with XYZ conditions or there was a sea vent with ABC mineral structure, right?
And from that pond or that pore or whatever, our first common ancestor came into being. The end, or I guess the beginning. But Laurie basically said, no.
No, actually, this is another fact about origin of life research is that anything we do in the lab, whether it's successful or not, it is only a description of what's possible as we've shown in the lab. But it's not the same as saying this is exactly what happened on Earth, because unless we have evidence from, say, the rock record, maybe you can't really know exactly what happened on Earth. That all that would tell you is now we have one possibility of how origin of life can occur under specific conditions.
Yes, we can't rewind time and see what happened. Anna agrees with Lori here. She says that finding a way to make life in the lab would not provide proof that early life on Earth was made the exact same way. But it would be exciting to know that there is at least one way of doing it. It would be exciting partly because it could show that life really could have arisen here on Earth earlier.
using only the ingredients that were already here, right, without needing extra help from a meteorite, for example. And it could give scientists a potential picture of what conditions might have been needed to make that life, whether that's vents or pools or ice or whatever. And all of that is great. But I'll be honest that my first reaction to all of this was like, if this research won't give us definitive answers about life on Earth's origins—
then why are scientists doing it? But Anna and Laurie and Michael, too, actually, they all told me that this research could point to something bigger than just where did life come from. It could tell us something more fundamental about life itself. Because if we humans, right, in just a few decades of tinkering, could find one possible solution, then
then maybe it's just not that hard to make life at all. And if it's so easy that even the descendants of a caveman can do it, then it's probably happened in a lot of different places in the universe. And that's simultaneously so terrifying but also so exciting to think that we're not alone. In fact, both Laurie and Anna are astrobiologists. So those are scientists who research the possibility of life elsewhere in the universe.
And they say that even if the work they're doing can never give us a perfect answer about life on Earth, it could give us clues about where to look for life elsewhere. If Anna's pools generate life, then researchers could look for similar traces of pools on a planet like Mars. But if Lori's vents end up generating life, then it might make more sense to focus on oceanic worlds that could potentially have vents.
So Europa, Jupiter's moon, has been talked about. And then Saturn's moon Enceladus is also talked about. And Enceladus has the plumes that go out into space. And so missions have measured the composition of the plume and some of their analyses have indicated there might be events. We don't know for sure, but there might be. Overall, though, whether researchers are more focused on the origins of life on Earth or finding life elsewhere...
There's still one mind-boggling idea at the heart of all this work that feels pretty consistent. This idea that if these researchers do finally succeed and make this big leap, they will have made life from scratch. And Anna especially took a minute to really grapple with that. Yeah, I'm always, I think right now,
I'm quite comfortable with just like looking at small pieces of the puzzle. But whenever I think about looking at all the pieces fitting together, it does really scare me. Not because she thinks this life would somehow become harmful or hostile or something. Like realistically, it's not going to be like creating a virus or something that's going to take over the world. But there is something uncanny about us humans making life.
To me, there's something kind of Frankenstein about it. So I guess I'm worried about there being some hubris here, maybe. But for Anna, that feeling of the uncanny comes from a very different place. She says that right now, when she looks at anything living under a microscope, even if it's just a bacterial life form, she knows that somehow, super distantly, she is kind of related to it. But if we create something,
that seems like it's alive in the lab, that's based on a totally different set of chemicals or the chemicals, you know, came from in the air, from gases and from liquids. It didn't come from another living organism. Then that's pretty much the first alien that any of us have ever met. The idea of an alien from Earth that humans made, it does make me feel a little bit scared. But also scary.
a little excited, and mostly just full of awe. On the next episode of our Origin series, another basic question with another clear and easy answer. So no one has been able to define life, and some people will tell you it's not possible to. That's next week.
In the meantime, if you want to read a lot more about the quest to make life in a bottle, Michael Marshall's book has so much history that we couldn't fit into this episode. It is called The Genesis Quest, The Geniuses and Eccentrics Who Tried to Uncover the Origins of Life on Earth. And Lori Barge and Anna Wang's research is really worth reading, too.
This episode was reported and produced by me, Bird Pinkerton. It was edited by Brian Resnick and Catherine Wells, as well as Meredith Hodnot, who I cannot emphasize enough how much Meredith keeps the wheels turning and the gears running on this show. We had sound design and mixing and scoring from Christian Ayala with help from Noam Hassenfeld. Zoe Mullick checks our facts and Manning Nguyen is likin' likin' a whole lot.
If you have thoughts about the origins of life, please send them to us. We are at unexplainable at Vox.com. And if you feel like leaving us a review or dropping some stars on your way out, it would be very much appreciated. Unexplainable is part of the Vox Media Podcast Network. And we will be back next week with more origins.