Science Friday - Undiscovered Presents: Spontaneous Generation

Episode Date: December 11, 2019

These days, biologists believe all living things come from other living things. But for a long time, people believed that life would, from time to time, spontaneously pop into existence more often—and not just that one time at the base of the evolutionary tree. Even the likes of Aristotle believed in the “spontaneous generation” of life, until Louis Pasteur debunked the theory—or so the story goes.  In a famous set of experiments, Pasteur showed that when you take a broth, boil it to kill all the microscopic organisms floating inside, and don’t let any dust get in, it stays dead. No life will spontaneously emerge.  His experiments have been considered a win for science—but according to historian James Strick, they might have actually been a win for religion.  This episode originally aired on Science Friday, when Elah joined Ira Flatow and science historian, James Strick, to find out what scientists of Pasteur’s day really thought of his experiment, the role the Catholic church played in shutting down “spontaneous generation,” and why even Darwin did his best to dodge the topic.   FOOTNOTES Though Darwin was bold enough to go public with his theory of evolution, he seemed to shy away from the spontaneous generation debate. But his theory inevitably invited the question: if life could spontaneously arise once on Earth, why not many times? James Strick writes about Darwin’s complicated relationship with spontaneous generation. The basic premise of Louis Pasteur’s famous swan-necked flask experiment is shown below. The swan necks let life-nourishing air into the flask, but kept potentially contaminating dust out. Louis Pasteur's spontaneous generation experiment illustrates the fact that the spoilage of liquid was caused by particles in the air rather than the air itself. These experiments were important piece (Credit: Public Domain via Wikimedia Commons)     GUEST James Strick, associate professor at Franklin and Marshall College   CREDITS This episode of Undiscovered was produced by Elah Feder and Alexa Lim. Our theme music is by I Am Robot And Proud.  Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

So Annie, a few months ago, I think you were out that day. Yeah. I found a tiny little maggot here in the recording. Gross. I didn't find it gross. I found it cute. I took a lot of pictures. I did wonder, though, how it got in here. We don't usually eat in here. We don't eat in here.

I do have a little chocolate wrapper. Ignore that. But if you were to tell me that that maggot popped into existence inside the booth, just materialized. I would say that was ridiculous because we know that life does not spontaneously appear willy-nilly. Except for a long time, we did believe that life could spontaneously arise. We called it spontaneous generation. Spontaneous generation is your textbook example of an idea that was wrong, and that scientists with their brilliant experiments disproved. At least, that's how I thought this story went. Earlier this year, I went on Science Friday where Ira Flato and I talked to a science historian. And we learned that how we came to believe what we believe today about spontaneous

generation, it actually has as much to do with science as it does with religion. Here's that story. This is Science Friday. I'm Ira Flato. And for the rest of the hour, we're diving into the vaults of science history because the hosts of our podcast Undiscovered are working on a new series. It's all one of my favorite subjects, all about science history. And co-host Ella Fetter is here to tell us about it. Hey, Ella. Hey, Ira. Yeah, me and my co-host Annie Minoff are really big science history buffs like yourself. And recently we got thinking about all of the scientific ideas that we used to think were true, you know, that we'd had accepted as good, solid science until one day we didn't believe them anymore. We're thinking about old miracle cures or outdated beliefs about the universe, you know, ideas that are often punchlines today.

But we wanted to give them a closer look. You know, why did we believe in these ideas in the first place? What had us convinced? And then what did it take to change our minds? That's what this upcoming series is all about. And today we're talking about spontaneous generation. It's really fascinating. Yeah.

So one of the basic ideas in biology is that every living thing comes from another living thing. You know, a horse comes from horse parents. An oak tree comes from an oak tree's acorn. an amoeba comes from another amoeba that has split in two. And if we work our way all the way back through evolution, all living things come from an original living thing. But for a long time, people believe that some living things didn't have parents. They just spontaneously sprang into life.

We called it spontaneous generation. You might have learned about this in high school. Yeah. So if you kept reading, you would have learned about how a scientist named Louis Pester disproved this idea, you know, science for the win. But it turns out that history is never that simple. You know, instead of a win for science, this might have been a win for religion. My guest is here to fill us in on the story behind the story.

James Strick is a professor of science technology and society at Franklin and Marshall College in Lancaster, Pennsylvania. Welcome to the show, Jim. Thanks. It's nice to be here. So you were a high school teacher for a while. So you know the textbook version of Spontaneous Generation pretty well. Can you give us the short version of it? Well, spontaneous generation really has been used most of the time to mean living things coming into being from non-living starting materials. But the upshot was that life was spontaneously coming into existence.

It didn't necessarily have living parents that brought it into being. That's right. So today we think of this as an idea that's been thoroughly debunked. It's very, very wrong, obviously wrong. But for over 2,000 years, a lot of very smart people believed in spontaneous generation, going all the way back to Aristotle. Yeah, Aristotle's certainly the best biologist of his day in ancient Greece and a real astute observer of nature. When he saw things like eels and frogs and tiny fish emerging from muddy riverbanks in the spring, it seemed pretty clear to him that you had a case of living things coming into being without parents

and that it was the influence of the strengthening sun, an element from the sun that he called Numa, that interacted with the mud of the riverbank to make it capable of producing new life when otherwise it wouldn't be. So he was only talking about small living creatures, not elephants and things like that. Nothing larger than frogs or eels, but to many people that already seems stunning enough in today's context. So you see these creatures coming up out of nowhere, it seems like they are just spontaneously emerging. But the Catholic Church was very against this idea. Why were they so against it? For most of the history of the Catholic Church, it was not opposed to spontaneous generation.

St. Augustine, for example, in the early 5th century, you know, one of the most important and influential church fathers who left a lot of writings, had no problem at all reconciling spontaneous generation with Catholic doctrine. He thought that God had put seed principles into certain kinds of matter at the beginning of creation, and that meant that over time they would unfold. and develop into living things. But it's only in the late 17th century when there really comes to be a sharp conflict between the dominant Catholic doctrine and the doctrine of spontaneous generation. Church is moving away from Aristotelian physics

because of all the new discoveries of the scientific revolution. But there's also new doctrines of pre-formation and pre-existence to explain where living things come from. They work with Genesis in a way, but not in a way that is compatible with spontaneous generation. It conflicts with this doctrine that all generations of organisms were created at the beginning, serially encased at like Russian dolls within the eggs or the sperm of the very first member of that species.

But also, as you get into the early 18th century, spontaneous generation is seen to potentially be an underpinning for philosophical materialism. The idea that matter alone contains everything necessary to generate life, mind, and that things like the soul and the afterlife are an illusion. So it kind of seems to cut God out of the equation. You can have life coming up from non-life. I could see why they would object to that. So in the 1800s, you get a showdown between two scientists. You have Louis Pasteur and somewhat less famous today, Felix Pouschet, over this idea of spontaneous generation. What happened?

Poucher, in the same year that Darwin's origin of species came out, 1859, Pousche published a book-length report of many, many experiments that he had done that seemed to validate the possibility of spontaneous generation, at least for microorganisms, even if not, for anything larger or more complex than that. The French Academy of Sciences, the most prestigious body of scientific opinion in France at the time, responded to this by posing a competition. There was a prize of 500 francs for the winner. They said, we challenge every scientist in France to present experiments that can clarify the subject of spontaneous generation. And essentially, Poucher's book, he entered as his entrance into this competition. and the French Academy, I guess, was waiting to see whether somebody would come in on the other side of the story and claim to have experiments that disprove spontaneous generation. That torch was taken up by a young, at the time, relatively little-known chemist named Louis Pasteur.

So Pousier had claimed to demonstrate that spontaneous generation was real. What was Pestor's problem with Pouche's demonstration? Pouche's main line of evidence was what are called infusion experiments. meaning you infuse or soak something in water, you boil it extensively to try to make sure that nothing that might have been previously alive could possibly still be alive in there. You boil it in a sealed container for an extended period of time, and then you let the infusion cool down in the sealed container. And if over time the results in there become turbid, cloudy, then you judge that there's a growth of microorganisms occurring. and in Poucher's case, you claim that that proves those microorganisms must have been produced by spontaneous generation. Pester did not think that Pousier's experiments were sufficiently precise, as he put it.

He thought that Pousier had not adequately sealed his containers to prevent the ability of microbes getting in from the outside. And Pester believed that microbes are widely distributed through nature, riding around for one thing, on dust particles everywhere. So Pasteur thought that if he could somehow duplicate Pouche's infusion experiments, but find a way to make sure that dust was kept out, that he could show that in those infusions, you'd never see the result turned turbid. There'd never be the growth of microorganisms in there.

And he came up with a really bright idea. He created what were later called swan-necked flasks. He heated up the neck of the glass. flask that the infusion was in in a Bunsen burner flame while the infusion was boiling and drew the neck out into a long curved shape where it had a dip in the curve before finally opening with a small opening to the outside air. And in those flasks, when Pester boiled them, never in any of his publicly reported experiments did he ever see any growth of microorganisms. So the French Academy of Science is pronounced Pasteur's experiments decisive and judged that Pasteur was right that Pousche had not

prevented the admitting of dust particles carrying microorganisms because he hadn't adequately sealed his flasks. And therefore, Pester's experiments proved that spontaneous generation was impossible. So it was a slam dunk then? That is how it is described in most textbooks, and that is how it was described by the French Academy of sciences at the time. The interesting thing is that scientists at the time split maybe close to 50-50 on whether they found this persuasive or not. An awful lot of scientists, not just Pouchet and his allies, but for example, Richard Owen in Britain, one of the premier comparative anatomists of the day and in some ways an opponent of Darwin in many parts of the evolution debate, Owen said

pointedly that it's really interesting. They don't seem to have proven, Pasteur doesn't seem to have proven anything other than that dust is a necessary ingredient for spontaneous generation, just as Poucher claimed. And the French Academy is premature in declaring Pasteur's experiments decisive. And Owen was not the only scientist in other countries who had that point of view. If it wasn't a slam dunk and a lot of scientists subjected, why did the account Academy of Sciences declare this a case closed. This is a time of a politically very conservative government in France that came to power in 1850.

And Louis Napoleon, the nephew of the famous Napoleon, he declared himself emperor and was supported by most of the conservative political forces in France, including the Catholic Church. So the Pasteur-Poucher controversy is taking place at a time of politically a very conservative government in France. This French Academy of Science is a government-appointed body, and therefore under considerable government influence in terms of its point of view, had appointed a jury to judge the Pastor Poucher competition, and a couple of the people on the jury had publicly before stated that spontaneous generation is absolutely impossible and would be an outrage against all morality in Christian society if it were proven to be true. and yet they were considered to be able to be objective judges on this commission. And they wanted to declare this case closed and settled,

even when many scientists considered the experimental evidence, as we say, underdetermined. After the break, we learned how Darwin did his best to avoid the spontaneous generation debate. Darwin's origin of species came out in 1859. Not long before Pasteur's famous experiments were declared the winners, that had debunked spontaneous generation. This whole topic is kind of awkward for Darwin. Here's James Strick again. If you read Darwin's book and are half awake,

you have to realize by the time you get near the end of the book, you know what this guy is saying is the further back in time you go, the fewer and fewer common ancestors there are. And if you go back far enough, all living things must be descended from someone single common ancestor, or at most a tiny handful of original ones, And so the book is kind of begging the question, where did that one come from? Many people perceive Darwin's book to be a project about getting the supernatural out of the life sciences.

This question is so loaded, and Darwin avoids it for almost the entire length of the book. And then on page 484, almost to the very end, there's one throwaway sentence on this subject. And what Darwin says, and I'm quoting, is, therefore I should infer that probably all the organic beings which have ever lived on this earth have descended from someone primordial form into which life was first breathed.

Amira Flato, this is Science Friday from WNYC Studios. And that's where scientists are now, right? Talking about that mystery chemical soup, that primordial soup on Earth that could have led to life. That's where modern origin of life research is right now, but imagine what an 1859 audience thought when it read that last

expression, someone primordial form into which life was first breathed. I mean, it's clearly biblical language, and it was clearly not selected unintentionally by Darwin. He's trying to dodge the question. He knows he's going to have quite enough difficulty already convincing a Christian audience to accept species change over time. He really doesn't want to... to tie his doctrine inseparably, this is my argument in my first book, to the argument that you have to believe if Darwin is right, there is no creator God. I guess in a sense this is as science history being just a subset of all history, usually the historians or the victors write the history. They sure do. And Pastor was conclusively declared the victor in France. And

A number of people in other countries took up the French Academy of Science's pronouncement. Textbook writers don't always follow the primary source literature that closely. They just listen to what the authoritative bodies of opinions say are the outcome of these debates. And so for generations of biology textbooks written since the 1860s, it has been copied practically word for word from the French Academy's pronouncement that these experiments of Pasteur approve once and for all. that life can never possibly come into being from non-life. You know, if you're a modern origin of life researcher,

obviously that's not right. You obviously believe that under some circumstances and under the conditions that existed on the primitive earth, it must have been possible. Origin of life research in the 1870s, early 1880s, kind of went in the tank for an extended period of time as a result of the French Academy of Sciences pronouncements about the Pester-Poucher debate.

That's about all time we have. I want to thank James Strick, Professor of Science Technology and Society at Franklin and Marshall College in Lancaster, Pennsylvania, for joining us. And also Ella Fetter, co-host of our Undiscovered Podcasts, who's hard at work on a new series all about the failed ideas of science history, right? Thanks, Ella. Thanks for having us. And we'll be hitting the road again in August.

This August coming to San Antonio. Yeah, join us Saturday, August 10th for Science Friday Live from the Lone Star State. We're going to talk about science stories in the San Antonio area. And believe me, there are lots of them. Plus, can't go to San Antonio without having live music more, all kinds of fun. That's Saturday, August 10th, not Friday night, Saturday night, August 10th, info and tickets at ScienceFriday.com slash San Antonio. And if you're saying, hey, what about an event near me? You can visit the events page.

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Yes, SciFri at Science Friday.com. Have a great weekend. I'm Ira Flato in New York. Undiscovered is produced by me, Ella Fedder. And me, Annie Minoff. Our senior editor is Christopher in Taliatta. Ira Flato is the host of Science Friday. Hear more at Science Friday.com.

And that is a wrap for Undiscovered. Thank you for listening. We are seriously going to miss you. You can find us both on Twitter at Annie Minoff and at Ella Fetter. Trust you to look up those spellings. And if you're sad that Undiscovered is over, you might be happy to know that we have a new podcast series coming out called Science Diction. It's all about science and words, and it's packed with science.

So stay tuned for that. It's coming out next year. And actually, if you want to get a preview, there's already a science diction newsletter. You can find it at sciencefriady.com slash science diction. Oh, and one more thing. We still have undiscovered merch, which I think at this point is pretty much exclusive undiscovered memorabilia. We have a notebook and t-shirts. You can find them at sciencefriiday.com slash store. So if you want to get those, Now is the time. It's really tiny. It couldn't have hurt you. I think I have the photo somewhere. I never showed them to you? No.

I never knew about this. You did it? No. Where were you that day? Maybe you were working from home. It was really cute. Had nothing to eat in here, though. I did worry a little.

Did I lose it? Where did it go? I don't know. Okay. So Annie, a few months ago...