Nettie Stevens and the Discovery of Sex Chromosomes

Daniel and Kelly explore the oft-forgotten scientific contributions of Dr. Nettie Stevens, who discovered that chromosomes are responsible for determining an organism's sex. See omnystudio.com/listener https://omnystudio.com/listener for privacy information.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Daniel Whiteson?

  This is an iHeart Podcast. Guaranteed Human.

• 0:07Speaker 01

  That sound? That's pro squash. Some of the fastest rallies in sport played inches from the crowd. The National Squash League is back in full swing for season four. The sport is heading to the 2028 Olympics for the first time, and you can see it up close right now in a city near you. Watch every match for free on YouTube. Search National Squash League and hit subscribe or follow live updates on Instagram at NSL.Sport.

• 0:35Speaker 02

  Cash flow crunch? OnDeck's small business line of credit gives your business immediate access to funds up to $200,000 right when you need it. Cover seasonal dips, manage payroll, restock inventory, or tackle unexpected expenses without missing a beat. With flexible draws, transparent pricing, and control over repayment, get funded quickly and confidently. Apply today at ondeck.com. Funds could be available as soon as tomorrow. Depending on certain loan attributes, your business loan may be issued by OnDeck or Celtic Bank. OnDeck does not lend in North Dakota. All loans and amounts subject to lender approval.

• 1:06Speaker 03

  Wait, I came in for two things. How is this $47? All right, we're gonna need a plan here.

• 1:14Speaker 04

  Just start simple with Bank of America Advantage Safe Balance Banking. No overdraft item fees, no monthly maintenance fee if you're under 25.

• 1:23Speaker 03

  Oh, that's actually really simple.

• 1:26Speaker 04

  Safe Balance Banking, one less thing to figure out. Learn more at BofA.com/simplebanking. Terms and conditions apply. Bank of America and a member FDIC.

• 1:36Speaker 05

  Hey, I'm Niall Rogers. This fall, I'll be driving across the country meeting some of today's coolest and most fascinating artists. We'll explore the stories before the moments that changed everything. Because every musician remembers the moment where it all began. Experience Before the Moment, a Lincoln original series on the iHeart Radio app, YouTube, or wherever you get your podcasts.

• 2:13Kelly Weinersmith?

  Hello there, friends! Heads up, as I'm sure you can tell from the title of today's show, we're talking about the birds and the bees again, so keep that in mind as you decide whether or not you want to listen to this with your kids. Also, today, when we use the word "sex," we're specifically referring to "gametic sex," which is to say we're talking about whether or not a person produces sperm or eggs. Okay, let's get started. About 2,300 years ago, Aristotle postulated that babies come from a mixture of male semen and female blood that mix together in the uterus. To explain how this mixture of fluids turned into either a boy or a girl child, Aristotle pointed to heat.

• 2:55Kelly Weinersmith?

  "You see," he argued, "all embryos start by developing into boys, but if not enough heat is present, then that development will stop, and you'll get a girl instead." 500 years later, and we still hadn't made loads of progress. Galen, a famous Greek physician and philosopher, had a much better sense of human anatomy, but was still focused on this heat thing. Ovaries, he argued, were actually just testes that hadn't experienced enough heat to make it through the journey to the outside of the body. By the early 1900s, we had learned a lot. Gregor Mandel had done his experiments in pea plants, so we knew that traits could be inherited from parents.

• 3:37Kelly Weinersmith?

  And we were starting to get an inkling of where the blueprints for that inheritance were being stored. We had seen chromosomes inside of cells, but had not yet tied those chromosomes to the inheritance of specific traits. And this is where Nettie Stevens comes in. Nettie, a rare PhD-holding woman scientist at the start of the 20th century, peered into the cells of insects and made an exciting discovery. One pair of chromosomes were different sizes! If you got the smaller chromosome, you were a male. If you got the bigger of the pair, you were a female. Not only had she discovered what went on to be called the X and the Y chromosomes, but this was the first time a particular trait had been tied to a particular chromosome.

• 4:22Kelly Weinersmith?

  Today, we talk more about Nettie Stevens's life and how she came to make this amazing discovery. Welcome to Daniel and Kelly's Extraordinary Universe.

• 4:44Daniel Whiteson?

  Hi, I'm Daniel. I'm a particle physicist and I'm very excited to get into the messy questions of biology.

• 4:51Kelly Weinersmith?

  I'm Kelly Wiener-Smith. I'm a biologist and wow, these questions really can get very messy. There's a lot we haven't figured out here, but I'm excited to talk about the early studying of how we determine if you end up making sperm or eggs.

• 5:05Daniel Whiteson?

  Messy questions, messy answers, messy methods. That's what biology is all about. Getting gooey with it.

• 5:12Kelly Weinersmith?

  I like the getting gooey with it part. I don't know about the messy methods, but I'll let that slide.

• 5:17Daniel Whiteson?

  I didn't mean sloppy. I mean that sometimes you literally get gooey. I mean, you come home with goo all over yourself, right? You're standing in a dumpster full of goo.

• 5:25Kelly Weinersmith?

  Yeah, no, there have been a couple of instances where I've been like, how did I get fish guts in my hair? And I discovered it later in the day and Zach was just absolutely appalled. And yeah, marrying a biologist is really gross stuff.

• 5:39Daniel Whiteson?

  I think it's underappreciated out there by the general public, how much the methods and the day-to-day work decides where you end up in science. Because you know, like, you're interested in the questions of biology, but I'm imagining you're not answering the deep questions of biology every day. Mostly, you're having fun working with fish guts or whatever. And so you got to enjoy that bit. And you know, I spend most of my time writing programs on the computer and I enjoy that bit. So it's like, you know, what kind of messiness do you like determines what kind of science you do, probably more than your inherent curiosity about the universe.

• 6:11Kelly Weinersmith?

  Absolutely. And I don't necessarily know that we tell students that enough. Like, when I introduced students to working with me when I was a grad student, I mentioned like a bunch of undergrads and I'd be like, look, straight up, a bunch of your time is going to be spent in a room that smells awful, like a combination of dead fish and formalin, or like staring and trying to count tiny little items under a microscope. And if you care about the question, you will love every second of that. But if you don't care about the question, you should find a different field because you're going to be miserable. And some of them dropped out not that long after, but it's good to find out early. Do you like that kind of stuff or do you not?

• 6:46Daniel Whiteson?

  And sometimes you can care about it. The question, but just not really enjoy the day to day work of it. You know, my first experiences in research were like plasma physics. And I was like, hey, I'm going to figure out fusion and save the world. And I definitely still care about that, but I find vacuum systems and plasma machines annoying. And I did not have a good time that summer. Thank you to those physicists out there who mentored me that summer, but I was deeply bored.

• 7:14Kelly Weinersmith?

  You really got to try this stuff out when you're an undergrad as much as possible. Like, I thought I was gonna love molecular work because I would, it would be like an episode of like CSI. You know, we're in there in their like fancy labs and they're pipetting to find amazing answers. And I hate pipetting. I'm miserable at it. My hands hurt, they get tight, I overthink everything. Doesn't matter how great the music I'm listening to is while I'm doing it. Like, I cannot get through it. And so I just, I stopped doing molecular work.

• 7:38Daniel Whiteson?

  Wait, but do you actually musical montage your way to an answer sometimes? You're like, I'm gonna jam through this, let's put on the music and dot, dot, dot, there we are. I love when they do that in TV shows.

• 7:47Kelly Weinersmith?

  Someone told me like, look, you're overthinking it. If you just flow, it'll be fine. So pick some music you can flow to. And I lost like a thousand dollars because I messed up a bunch of kids. Cause I have to do more than just flow. I'm not a person who flows, I guess. But, you know, this is a good intro, actually, perhaps even accidental. Because the woman that we're talking about today, there were maybe 50 or more species of insects where she went through and she like crushed cells, stained cells and watched different stages as they divided to produce sperm. And I read one of her papers and it had something like 250 plates where she had like very carefully drawn what was happening with chromosomes and these various stages.

• 8:31Kelly Weinersmith?

  That must have taken many, many hours and been incredibly tedious work and counting to track all the chromosomes and how they were matching up with one another. And, you know, the patience that it must have taken to even just like extract the gametes out of like a tiny cricket so that you can look at them. Like, that takes a lot of skill. So, yes, she really persisted through a lot of what would have been very boring work to many of us. Maybe she loved it, I don't know, but I. I looked at the plates and I immediately was like, whoa, I would have been way too bored to do this.

• 9:02Daniel Whiteson?

  Maybe she was jamming to the hip music of the day the whole time, right? That's sort of like a lost question in history. What music did famous scientists listen to while they did all their important work?

• 9:13Kelly Weinersmith?

  Yeah. Did we have records in the early 1900s? We must have, right?

• 9:16Daniel Whiteson?

  Yeah, I think we did for sure.

• 9:18Kelly Weinersmith?

  Jamming to some record? Nice. I like the idea that that's what was happening. Too bad she couldn't listen to our podcast.

• 9:26Daniel Whiteson?

  Somebody out there write a book about the history of music listened to by scientists.

• 9:32Kelly Weinersmith?

  I don't know if that's sound career advice. I don't know how big the audience is for that book.

• 9:37Daniel Whiteson?

  I want to read that book, so I don't care. Somebody out there write it.

• 9:39Kelly Weinersmith?

  OK, great. Sounds good.

• 9:42Daniel Whiteson?

  Today, we're not talking about music, but we are talking about pioneering scientists who made incredible discoveries that influenced the way we think about big, important questions in our life. In this case, big, important, messy biological questions.

• 9:56Kelly Weinersmith?

  Yes, and we're specifically focusing on scientists that most people have never heard of, despite the fact that they made absolutely profound discoveries about the way that life works. And so we pose to our audience the question, what was Nettie Stevens's big biological discovery? And if you want to answer our questions, contact us at [email protected] and we'll add you to the list and we'll send you our question before an episode and you can give us your best guess. All right, let's hear what our audience came up with this time.

• 10:28Speaker 03

  Nettie Stevens discovered that as long as radioactivity is negligent, a cellular mechanism will be able to achieve stasis for a nominal period or duration of time. I'll be honest, I've never heard of Nettie Stevens. Well, this one's short. I have no idea. Did Nettie Stevens invent the Nettie pot that allows you to irrigate the biological war zone happening in your sinus cavity as long as you hold?

• 11:00Speaker 05

  Hold your head at the proper angle, otherwise you end up with a salty slimy soup for lunch.

• 11:08Daniel Whiteson?

  My completely uninspired guess is that she discovered that the Loch Ness monster is real.

• 11:20Kelly Weinersmith?

  All right. So to be clear, despite the profound confidence that we're hearing in that very first explanation, that is not correct.

• 11:28Daniel Whiteson?

  Is that totally manufactured or is that somebody else?

• 11:31Kelly Weinersmith?

  Yeah, no, no, that's totally manufactured. He wrote and made some sort of joke about like, you know, the more confident you sound, something like that. So.

• 11:37Daniel Whiteson?

  That sounds like a chat GPT answer, right? Total confidence and total nonsense.

• 11:42Kelly Weinersmith?

  Sometimes chat GPT gets it right, but yes, often it's hallucinating, which this listener was perhaps also doing. She's not associated with the Nettie Potts. And then we had two listeners who had never heard of her.

• 11:53Daniel Whiteson?

  Well, it sounds like there's a lot of folks out there who need to know more about Nettie Stevens and what she contributed to our understanding of the biological world. So let's go, let's find out, let's hear all about Nettie Stevens. So Kelly, tell us, who was Nettie Stevens?

• 12:08Kelly Weinersmith?

  And I'll do my best to sound confident so that even if I'm wrong, everyone will believe it.

• 12:13Daniel Whiteson?

  Well, I'm pretty sure you're not an AI. I mean, I've known you long enough. I think I would have figured it out by now.

• 12:17Kelly Weinersmith?

  I don't know. AI is getting pretty good. All right. So Nettie Maria Stevenson, she was born in 1861 in Vermont, and she was born to like a middle class family. And unfortunately, her mom died when she was pretty young. But she was lucky that she had a father who really wanted to invest in his daughter's education, and she also had a sister. And so he sent them to school. They went to West Ford Academy and she studied to be a teacher.

• 12:44Daniel Whiteson?

  Is this something that was unusual at the time? Like, did most women go to school? Did most folks living in middle class Vermont go to school? Or was it unusual for them to go?

• 12:53Kelly Weinersmith?

  It was pretty unusual. So training to be a teacher wasn't super unusual. Training to be a scientist definitely was, but it was still fairly unusual. And so she leveraged this early education as a teacher so that through various points in her life, she could teach for a while to save up money so that she could afford to follow her dream, which was to become a scientist. And so she would teach for a while, save up money. And at one point after saving her money in 1896, she started at a new school that, you know, maybe you hadn't heard of called Leland Stanford Junior University. It ends up becoming Stanford. And she gets a bachelor's and a master's there.

• 13:33Daniel Whiteson?

  Wow. And how many women are attending Stanford in the late 1800s?

• 13:37Kelly Weinersmith?

  Not many. I don't know the exact number, but there were not many. And as you'll see, like at one point when she gets recognized for her amazing contributions, she's on a list of the top 1,000 men in science.

• 13:53Kelly Weinersmith?

  And she was one of 18 women on that list. So to sort of give you some sense of how many famous women scientists there were at the time, there were 18 women who broke into this list of 1,000, and this was towards the end of her career.

• 14:06Daniel Whiteson?

  And did she also get married and have a family? Or did she have to choose between those paths?

• 14:11Kelly Weinersmith?

  So I wasn't able to find a lot of personal information about Nettie. I haven't like been able to find a biography that people wrote about her, the Encyclopedia Britannica, Wikipedia, everywhere you go, they pretty much say the same things. I found a couple of scientific papers talking about her early life and contributions, and they all just sort of like list off the same facts.

• 14:29Daniel Whiteson?

  Sounds like somebody who needs to do a deep dive and write a book about Nettie Stevens. We're like book projects out the wazoo on this episode today.

• 14:35Kelly Weinersmith?

  Absolutely. And she was connecting with a lot of major players in the field at the time. And so I think there'd be a lot of interesting information to go on and maybe like the letters of her advisor, who was ended up being a famous scientist, we'll talk about him, like might have mentioned enough where you could get some more personal details. But anyway, there weren't a lot of personal details, but no, she did not end up getting married or having kids, and she ended up being buried with her dad and her sister. So science was her life, as far as I was able to tell.

• 15:02Daniel Whiteson?

  Married to biology.

• 15:04Kelly Weinersmith?

  Maybe she had some great hobbies and had some really cute dogs. But we don't really know.

• 15:09Daniel Whiteson?

  Well, it sounds like she had a really fulfilling and satisfying life. So go Nettie.

• 15:12Kelly Weinersmith?

  Yes. No, absolutely. So early in her career, she identifies two new species of cillia, but she ends up wanting to study more sort of genetic based stuff.

• 15:21Daniel Whiteson?

  What's a cillia, sorry?

• 15:22Kelly Weinersmith?

  These are tiny little eukaryotes, and cillia are like little hairs that they have on the outside of them. And so these hairs sort of are moving frantically to get them from place to place. And they're teeny tiny little things, and she managed to find two new species.

• 15:36Daniel Whiteson?

  And how exciting is that to find two new species of cillia? Is that like the kind of thing? We do every day because there's zillions of them like beetles? Or is it like a big breakthrough? Or what do you learn when you name two new species of cillits?

• 15:47Kelly Weinersmith?

  There's a lot of cillits. To name a new species, especially today, requires a lot of like precise measurements and studying the ecology of the animal and coming up with an argument about why it's different than anything that's been identified before. So it's really good practice for very careful measurements of different sort of like organ parts and getting really good at sort of like drawing things and tracking sizes and having a good eye for what's different between things. And so that was probably a really great skill for her. But I don't think anyone's ever won a Nobel for identifying a new cillit, unfortunately.

• 16:21Daniel Whiteson?

  It would be pretty silly to win a Nobel Prize for cillits.

• 16:23Kelly Weinersmith?

  I don't know about, oh, silly.

• 16:27Kelly Weinersmith?

  Maybe I am an AI. I'm not getting the jokes.

• 16:31Daniel Whiteson?

  Well, you know, I often am criticizing biology as like just being botany. Because I feel like the interesting bit of science is not, let's go out and describe what we see in the world. But it's the part where we harmonize, that we put it in context, we understand the differences, the distinctions, what those trends mean, right? Not just like, hey, here's a list of all the different silly bits in the world and we call them cillits. You know, and we do this in particle physics also, right? We have all these particles, we don't understand them, but we want to, right? We're asking those questions like, why do we have an electron, a muon, and a tau? So when somebody makes a new species, is it always interesting just having seen it? Or is it only because it raises these questions about evolution and the context and the history?

• 17:12Kelly Weinersmith?

  I think it's both. And actually, I feel like right now, especially in my field, it's underappreciated when you describe a new species, because there is such an emphasis on like, how does this fit into bigger theories? And like, that's the kind of stuff that gets you an NSF grant. And to be honest, I feel like we are racing way ahead on the theory and not stopping to do enough cataloging so that you actually have the data you need to test these theories? We should have a whole episode on that, but we're getting off topic.

• 17:37Daniel Whiteson?

  All right.

• 17:38Kelly Weinersmith?

  I would argue that both of those things, the cataloging and the big theories, you can't do one well without the other, they're both critical.

• 17:44Daniel Whiteson?

  You need botany and philosophy to come together in harmony. All right, but let's get back on track with Nettie. So she's Discovered two new silly kinds of sillits. What happens to her next?

• 17:54Kelly Weinersmith?

  She saves up some money again, and then she ends up going to get her PhD at Bryn Mawr.

• 17:58Daniel Whiteson?

  And she's saving up money because she's paying to do this? So she's like paying for her education?

• 18:03Kelly Weinersmith?

  I think she probably had to pay for things like her housing. I don't know what kind of fellowship they offered her. But I do know that when she got there, she was an absolute rock star and she got the Bryn Mawr President's European Fellowship. So she got to go to Naples to work with this famous guy doing genetics work at the time. So she was like an absolute rock star and she wraps up her PhD. And this is when stuff really starts going. So she starts getting interested in whether or not chromosomes are what determines if you end up making sperm or eggs. And she gets a big grant to answer this question. And when we come back from the break, we're going to talk about what the prevailing theories at the time are for what gives you boys and what gives you girls.

• 18:53Speaker 01

  That sound? That's the National Squash League. Pro teams, the world's best players, and rallies so fast you'll forget to breathe. Season four is in full swing and every match streams free on YouTube. Big hits, bigger rivalries, and a front row seat from wherever you are. Watch every match for free on YouTube. Search National Squash League and hit subscribe or follow live updates on Instagram at NSL.Sport.

• 19:21Speaker 02

  Cash flow crunch? OnDeck's small business line of credit gives your business immediate access to funds up to $200,000 right when you need it. Cover seasonal dips, manage payroll, restock inventory, or tackle unexpected expenses without missing a beat with flexible draws, transparent pricing, and control over repayment. Get funded quickly and confidently. Apply today at ondeck.com. Funds could be available as soon as tomorrow. Depending on certain loan attributes, your business loan may be issued by OnDeck or Celtic Bank. OnDeck does not lend in North Dakota. All loans and amounts subject to lender approval.

• 19:52Speaker 05

  Hey, it's Niall Rogers, host of Before the Moment, a Lincoln original series. I'm driving across the country, meeting some of today's most fascinating artists. We're exploring the stories before the moment that changed everything. This week, I'm joined by my friend, John Legend. How does music actually enter your mind? I'm not sure why or how the music comes to me, but I think.

• 20:19Speaker 03

  People who love music and write music, our brains are just filled with music.

• 20:24Speaker 05

  Right.

• 20:25Speaker 03

  Like, we have listened to so much music, we've been a part of so much music. I think of the story that I want to tell, the mood that I want to create with the music, start playing chords, see where they lead me.

• 20:36Speaker 05

  Sometimes I'm just not even thinking about music, right? And I hear this little thing and I go, oh, that could be this.

• 20:46Speaker 03

  You know, you just have to be ready for when the inspiration hits.

• 20:49Speaker 05

  And it comes.

• 20:49Speaker 03

  Yeah.

• 20:50Speaker 05

  Experience before the moment. The Lincoln original series on the iHeart Radio app, YouTube, or wherever you get your podcasts.

• 21:08Kelly Weinersmith?

  All right, we're back. So let's take a bit of a historical perspective to figure out where we are after Nettie Stevens has finished her PhD. So she finished her PhD in 1903. So over 200 years earlier, Anton von Leyen-Hooke had looked at his sperm underneath the microscope and the sperm of dogs also. So we knew sperms existed for over 200 years.

• 21:29Daniel Whiteson?

  And Lewin Hooke is the guy who discovered the cell originally, right? He's like first dude to look in detail at microscopic biology.

• 21:36Kelly Weinersmith?

  Von Leyen-Hooke was not the first one to see cells. That was Robert Hooke. Von Leyen-Hooke saw little organisms in pond water. He called them animocules. And he also did a lot of exploring for little animocules in, on, and from his body. So he was the first one to observe sperm.

• 21:55Daniel Whiteson?

  I love the word animocules. That's awesome.

• 21:58Kelly Weinersmith?

  It is, and it's also cute. And I like cute.

• 22:01Daniel Whiteson?

  Exactly. Like little tiny animals, how nice.

• 22:04Kelly Weinersmith?

  Yeah.

• 22:04Daniel Whiteson?

  So was he surprised to discover like wiggly things in his semen? Like, is this a big shock to him or was he looking for that?

• 22:11Kelly Weinersmith?

  Yeah, I think he was a little bit surprised. And there was some question about whether or not that was like contamination and the like fluid around the sperm is what was actually important for making babies. And so I think he was surprised and he wrote it up, sent it to the Royal Society and turned out, yeah, that those sperms. Or important in making babies.

• 22:31Daniel Whiteson?

  All right, cool.

• 22:32Kelly Weinersmith?

  And then about 150 years later, we have the first like description of mammalian eggs. So for a while, actually, we use these phrases male sperm and female sperm. And the idea was that out of the ovaries came sort of the female equivalent of sperm. And it took a while before someone actually observed eggs. I think they had dissected a rabbit to see eggs for the first time. But so by about 1825, we have seen eggs, we have seen sperm.

• 22:58Daniel Whiteson?

  And how do you know what an egg is? Have you recognized it's like, oh, this is obviously the counterpart to the sperm? Like, isn't it just another cell in the body?

• 23:06Kelly Weinersmith?

  Yeah, that's a good question because it would be another 50 years before we saw the fusion of sperm and egg to come together to produce like an embryo. But I think that it was a series of experiments that were done on rabbits where they were sort of dissected at different times. And they observed like the same kind of cell sort of moving out of the ovaries and into the uterus. And I think that that's what they, when they were like, okay, we don't have female semen. We've got this little thing that like makes a journey from the ovary into the uterus. And I think that they had seen bird eggs, which sort of gave them like this egg sort of idea. I believe that that's the history of how we observed eggs.

• 23:44Daniel Whiteson?

  And this sort of the broader context, like people are wondering how sex works and how you end up with boys or girls. And there's already this prevailing concept that it could be determined by something like microscopic. You know, where are we in like relation to germ theory and this idea that like there are tiny invisible bits in biology that can have big macroscopic impact?

• 24:03Kelly Weinersmith?

  So I think the prevailing theory is that like, yes, these things can come together and they can be important in the production of offspring. But how does that end up as a boy or a girl is still an open question. And so one of the theories from like 1748, there was this book by a French anatomist. Whose last name was Couteau and the book was called The Art of Having Boys. Because obviously, that's what you'd want to be doing.

• 24:29Daniel Whiteson?

  Mm hmm.

• 24:30Kelly Weinersmith?

  And the idea was that sex organs come in pairs. So males have two testes, females have two ovaries. And so it must be that one testy is important for making males and one makes females. And they hang at different heights. And so you should be able to figure out which one makes boys and which one makes girls. And so.

• 24:50Daniel Whiteson?

  This is also very logical and also off base.

• 24:54Kelly Weinersmith?

  Well, this book actually went through four additions, which is more additions than my book has gone through. So this was apparently better than anything I've done in my life. So he actually proposed that if you want boys, you could figure out which testes makes boys and which one makes girls, and you could remove the one that makes girls to make sure you make boys. But for the more timid, he notes that since there's one ovary that makes girls and one ovary that makes boys, you could instead just have the woman lay on one side. So gravity will send the sperm to the ovary to get the child you want.

• 25:25Daniel Whiteson?

  Wow.

• 25:25Kelly Weinersmith?

  So none of this works. Don't trust bestselling authors.

• 25:29Daniel Whiteson?

  That's a more general longstanding lesson.

• 25:31Kelly Weinersmith?

  Yeah.

• 25:32Daniel Whiteson?

  So people understand it's something microscopic, but we want to understand the more detailed mechanism. And that's why people are using microscopes and dissecting stuff.

• 25:40Kelly Weinersmith?

  Yes, right. And while we're on the topic of what ends up giving you boy and girl babies, as classically defined at the time, nutrition was another popular idea. And so the idea was that if you are underfed, you'll produce boys. And I think the argument there is that sperm, they're like smaller and they're chasing to get to the bigger eggs. And so if you're not eating enough, you produce these smaller sperm things and it's confusing.

• 26:06Daniel Whiteson?

  Man, if we had social media back then, there would have been lots of crazy influencers telling people how to have boys or girls.

• 26:11Kelly Weinersmith?

  Oh, my gosh, so many. But, you know, to be fair, so like in the animal kingdom, whether or not you get an individual who produces eggs, an individual who produces sperm, or an individual who produces both, so hermaphrodites of different types, is actually very complicated. And so this idea for nutrition wasn't completely crazy. So like they had taken a bunch of sheep and they malnourished some and they overfed others and they ended. Up with 60% female offspring and 40% males. And then there were some, what they called lower vertebrates, where they did these experiments and the effects were even more pronounced. And so there are some species where nutrition sort of plays a role in whether or not you're more likely to get offspring that make sperm or offspring that make eggs.

• 26:55Kelly Weinersmith?

  And so they had made some observations that were consistent with this idea, but it just turns out that's not how most things work. And of course, that's not how humans work.

• 27:03Daniel Whiteson?

  All right, so Lowenhoek sees the sperm. People discover eggs. Couteau writes a nonsense book about the art of having boys. It's understood to be very complicated. How did Nettie get involved? What was her interest and what did she contribute?

• 27:17Kelly Weinersmith?

  Taking a very slight step back. In like 1865, Gregor Mendel did his pea experiments that you might have learned about in high school, but it was a long time ago, for me at least. So essentially he did all these crosses of pea experiments and he discovered that the traits in the like baby pea plants were being inherited from the parents. But it wasn't clear what material was passing that information from one generation to another. So he made these amazing contributions to science, which were promptly forgotten about. And nobody looked at it. Like, I think literally, so a long time ago, when books would be printed, sometimes you'd have to separate pages with like a little knife because of the way they were printed. And so Darwin had Mendel's book on his bookshelf, but the story,

• 28:01Kelly Weinersmith?

  and maybe this is apocryphal, but I've been told it like five or six times. So I'm going to go ahead and share it, was that he hadn't actually opened up the pages in his book where he would have learned about this inheritance stuff. So he could have learned about it, but he didn't. But anyway, okay. Gregor Mendel does this inheritance stuff. Everybody forgets about it. Around 1870, we first see genetic material. So it's called nuclein. We don't really know what it does, but we've now seen genetic material.

• 28:28Daniel Whiteson?

  Meaning that we've gone now inside cells. So not just like, here's a sperm, but we're like digging into the cell and finding the bits that carry that information.

• 28:36Kelly Weinersmith?

  Yes. Yep, exactly. But then by the early 20th century, so around 1900, Mendel is rediscovered by a bunch of scientists. And we're like, oh my gosh, okay. Traits are inherited from parents. We have good evidence for that, but what are the blueprints that are transmitting this information? And so now you can combine the fact that you've seen this stuff inside of cells and that feels like maybe that's the stuff that transmits the information. And so now people are starting to dig into that. And so this is the scientific background of where Nettie Stevens jumps in. So in 1891 Herman von Hanking, he's studying chromosomes. He's noticing that they almost always pair up, but he notices that there's this one thing that doesn't pair up and he calls it the X element. But he doesn't know what it

• 29:20Kelly Weinersmith?

  does. And this is before the 1900s when Gregor Mandel had been sort of rediscovered and his works had been rediscovered. So people at that time weren't really trying to connect the stuff that was in the cell to traits that got inherited across generations. So he's just like, oh, there's this thing and it kind of acts different than the other stuff. And he calls it the X element. About 10 years later, Clarence McClung notices the same thing and he changes from the like super X many awesome sounding X element to the accessory chromosome, which is a boring, which is so boring.

• 29:55Daniel Whiteson?

  It still has X in the title, right? Accessory chromosome.

• 29:59Kelly Weinersmith?

  I think we got to talk about your spelling.

• 30:06Kelly Weinersmith?

  But in 1902, he notices this accessory chromosome and he says, okay, look, it doesn't seem like all of the sperm cells are getting it. And so maybe this is important in determining who becomes a male and who becomes a female, because that's the most obvious difference between the organisms that he's studying is male and female traits. And he postulates incorrectly that the males are the one who gets this extra accessory chromosome. It increases the metabolism of the organism who gets it. And that's how you get males.

• 30:41Daniel Whiteson?

  So he's right on the edge of discovering this, but he gets it like basically exactly backwards.

• 30:47Kelly Weinersmith?

  That's right. But you know, I think so often when you study the story of how a scientific discovery comes along, what you want is like one person who out of the blue came up with the idea because that makes for a better story. But no, this just like almost all science is like a community sort of moving towards an answer. And there's multiple players sort of along the journey. So McClung is getting really close, but he gets it in reverse.

• 31:09Daniel Whiteson?

  I think that's almost always the case. Like if you go back and understand like Einstein's work, you see how many pieces he's pulled together from other folks and you see other people publishing the same idea like weeks after him done independently. Like it's almost always the case that science flows as a wave and there's somebody surfing at the very edge of it. And we like to write those dramatic stories. It's like single genius in the dark with a candle, you know, and a blanket to ward off the Scottish cold. But more often it's a big community effort.

• 31:39Kelly Weinersmith?

  Yeah, I think that wave is often made of many, many colleagues who are holding that person up and pushing them forward. It's not just one person. And that ends up being the case here, too. So Nettie Stevens, after her PhD, she got this big grant to study how those chromosomes might determine the sex of individuals. And in 1905, she publishes her seminal study, Studies in Spermatogenesis. And what she did was she looked at a bunch of different kinds of insects. So she looked at a species of termites, a species of sand crickets, croton bugs, and crucially, she looks at mealworm beetles. And what she does for each of them, and this is what we were talking about earlier, I said there were 200 plates where it was meticulously documenting where the chromosomes were going over time

• 32:22Kelly Weinersmith?

  and what was happening. And she was counting all the chromosomes. So she notes accessory chromosomes in some of the species that she's looking at. But when she gets to the mealworm beetle, she's like, okay, when you pair up the chromosomes, there is a pair where you have a big chromosome and a little chromosome. And I think that the individuals who get the little chromosome become the males and the ones that get the big chromosome become the females. And part of why I think that is because when you look inside the adult cells, forget the sperm, let's look at adults, in those adults, the males have that little chromosome and the females have that big chromosome. So that must be the thing that determines sex. And getting that big X, that makes you a female. McClung said it made you a male, but that makes you a female.

• 33:05Daniel Whiteson?

  And is this what Nettie was studying? Is this what she was like out to figure out? How did she get interested in this question?

• 33:11Kelly Weinersmith?

  This was what she set out to discover. I think, you know, she was a person who was good at looking at tiny little things and making measurements and observations on tiny little things. And she was getting interested in genetics because this field was burgeoning and becoming exciting while she was working on her PhD. So like while she was working on her PhD, this was the time when Mendel's rules were being rediscovered concurrent with our discovery of some genetic material. So trying to tie those things together became something she was interested in. And actually, her PhD advisor ended up becoming a gigantic name. He's considered one of the fathers of modern genetics. So he ended up ultimately establishing like Drosophila as a major organism used for lab work. And he connected a bunch of different chromosomes to different traits.

• 33:56Kelly Weinersmith?

  And so I think it was sort of like in the air and she came from a lab that was sort of interested in these sorts of questions.

• 34:03Daniel Whiteson?

  Well, so this must have been a huge discovery for her, like to see such a clear answer to this question that's on everybody's minds.

• 34:10Kelly Weinersmith?

  Yeah, okay, that's totally true. It should have been a super big deal. It happened concurrent, though, in the same year that she published this. Edmund Beecher Wilson, who was another geneticist who was farther along in his career, he was looking at a different insect species. He was looking at the accessory chromosomes and he also said, hey, accessory chromosomes, these are what makes males and females and the female is the one that gets the X. So he came up with the same discovery in the same year. His paper got published a few months before hers.

• 34:45Daniel Whiteson?

  Oh, no.

• 34:46Kelly Weinersmith?

  I know, but they had been talking to each other. And so he references in an updated version of his paper, he references that like, hey, Nettie Stevens found the same thing. And actually she found this little Y thing. And so I believe they had been looking at insects that had slightly different systems for sex determination. So in some cases males had the Y and in some cases. Males were made by simply not getting anything. So the females got the extra X and the males got nothing. They were just sort of missing that information. And so they had both come up with this at the same time. They were both, it sounds to me like respectfully communicating their results to one another. And they just happened to submit and his came out a little bit before hers. But she's largely credited with being much clearer. And she went ahead

• 35:30Kelly Weinersmith?

  and took that extra step and looked in the cells of the adults and was like, okay, this thing that we're seeing in the sperm plays out in the adults. The adult males have the Y and the adult females have the X. But I don't actually feel like it's worth trying to decide like whose words were more firm than another. Like, I know we want one person to be out ahead of the other, but like, they both did really good work.

• 35:52Daniel Whiteson?

  Yeah.

• 35:53Kelly Weinersmith?

  Around the same time. And this is how science works. And, you know, joint credit seems reasonable to me.

• 35:59Daniel Whiteson?

  To me, the issue of these priority disputes is not who sent in their paper first, or who took longer in review and got it published first. It's just like, was the work independent? Because if you read somebody else's paper and then publish based on that, then you shouldn't get credit for their discovery because you're building on top of it. But if you figured it out in your own dink Scottish laboratory, you know, then you figured it out on your own. And if it's in parallel, you should both get credit. It doesn't matter if you published six months earlier or six months later. It's an independent piece of work.

• 36:29Kelly Weinersmith?

  I agree. But I mean, in the way that human stories always go, you know, people were talking to each other and Wilson had been at Bryn Mawr right before she got there. And her PhD advisor kept collaborating with Wilson. And so like, this is a question they all wanted to have answered. So they were all kind of working on it concurrently. And so there was a lot of discussion between them. Nettie made this really nice, really clear observation. Wilson also made some great clear observations. So, I mean, to me, it would be great if Nettie Stevens and Wilson were both known for the discovery of sex chromosomes. But you know, who got the credit?

• 37:05Daniel Whiteson?

  I'm guessing it's not Nettie Stevens because I'd never heard of her and neither had the listeners. So then is it Wilson?

• 37:10Kelly Weinersmith?

  No, it's Thomas Hunt Morgan. And after the break, we'll talk about why.

• 37:29Speaker 01

  That sound? That's the National Squash League. Pro teams, the world's best players, and rallies so fast you'll forget to breathe. Season four is in full swing, and every match streams free on YouTube. Big hits, bigger rivalries, and a front row seat from wherever you are. Watch every match for free on YouTube. Search National Squash League and hit subscribe or follow live updates on Instagram at NSL.Sport.

• 37:57Speaker 01

  Cash flow crunch? OnDeck's small business line of credit gives your business immediate access to funds, up to $200,000, right when you need it. Cover seasonal dips, manage payroll, restock inventory, or tackle unexpected expenses without missing a beat. With flexible draws, transparent pricing, and control over repayment, get funded quickly and confidently. Apply today at ondeck.com. Funds could be available as soon as tomorrow. Depending on certain loan attributes, your business loan may be issued by OnDeck or Celtic Bank. OnDeck does not lend in North Dakota. All loans and amounts subject to lender approval.

• 38:28Speaker 05

  Hey, it's Niall Rogers, host of Before the Moment, a Lincoln original series. I'm driving across the country, meeting some of today's most fascinating artists. We're exploring the stories before the moment that changed everything. This week, I'm joined by Miguel.

• 38:46Speaker 03

  My small experience with the discrepancy in the business of music made me angry in the best way, and I wanted to finish. So I started really leaning into my therapy, trying to get down to what matters now. Somewhere, Miguelito felt like he didn't have a place to say how he felt. And music was the place that I went to to say how I felt.

• 39:08Speaker 05

  Experience Before the Moment, a Lincoln original series on the iHeartRadio app, YouTube, or wherever you get your podcasts.

• 39:26Daniel Whiteson?

  All right, we are back from the break and Kelly just dropped a big bomb on us. Bring in a dark horse. Kelly, you can't just bring in a new character in act three without laying the pipe in act one. I mean, don't you have you taken screenwriting 101? Who is this Thomas Hunt Morgan fellow and why does he get the credit for Wilson and Stevens' independent work?

• 39:46Kelly Weinersmith?

  Well, I'm gonna try to not have my feelings hurt too much because I had mentioned Thomas Hunt Morgan earlier.

• 39:52Daniel Whiteson?

  Oh, no.

• 39:52Kelly Weinersmith?

  A couple of times, but you know, we were throwing a lot of names around, so maybe it didn't stick, but he was her PhD advisor.

• 39:58Daniel Whiteson?

  So Morgan is Stevens PhD advisor?

• 40:01Kelly Weinersmith?

  Yes.

• 40:02Daniel Whiteson?

  Oh, nice. No, I totally take it back. You absolutely did lay the groundwork, but like an excellent mystery novel, I overlooked the important clues.

• 40:10Kelly Weinersmith?

  Oh, man, maybe I'm the next Agatha Christie.

• 40:12Daniel Whiteson?

  Exactly.

• 40:15Daniel Whiteson?

  So is this the standard case of PhD advisor gets credit for grad student work? Is there gender stuff at play here?

• 40:20Kelly Weinersmith?

  There's definitely sexism at play here. First of all, it's kind of ironic because Morgan, at the time that Wilson and Stevens published their result, he was like not super sure about this sex chromosome thing. He was like, well, maybe that's not how it works. He still needed to be convinced at the time these results came out. But in 1906, there was a conference and both Morgan and Wilson were invited to give talks about their theories of how sex is determined. So how you end up with individuals that make sperm and how you end up with individuals that make eggs. But Stevens was not invited.

• 40:54Daniel Whiteson?

  And is Wilson already like a professor and Stevens is a grad student? Is that how it works?

• 40:58Kelly Weinersmith?

  Wilson is already a professor. Stevens has finished her PhD, but she's in a part of her career where she's having trouble getting the professorship that she deserves.

• 41:08Daniel Whiteson?

  Right.

• 41:08Kelly Weinersmith?

  So actually, it will take five, maybe seven years for her to finally get offered a professorship. So she gets offered a postdoc at Carnegie Institute, Washington, and then she gets to go back to Bryn Mawr as a research associate, but she doesn't get a faculty position. A couple of years later, they offer her that faculty position, but before she can accept it, she dies of breast cancer.

• 41:31Daniel Whiteson?

  Oh, gosh. All right. So.

• 41:35Daniel Whiteson?

  Before we dig into that tragedy, let's go back to the conference you were talking about where her advisor Morgan and her sometimes friendly rival Wilson both get offered big talks to give their theories of sex determination, but she doesn't. And she's also the most junior person of the three, right?

• 41:51Kelly Weinersmith?

  Right. And dying early is actually part of the story here.

• 41:54Daniel Whiteson?

  Oh, wow.

• 41:55Kelly Weinersmith?

  Wilson and Morgan both go on to become even more well-known scientists. Morgan, in particular, ends up doing amazing work on fruit flies, attributing particular genes to particular traits in these fruit flies. And when Stevens dies, Morgan writes her obituary.

• 42:13Daniel Whiteson?

  Oh, wow.

• 42:14Kelly Weinersmith?

  He writes her obituary in science, and he doesn't get all of it right.

• 42:18Daniel Whiteson?

  Oh, gosh. This is like a Morgan character assassination here. I feel like we need to have somebody from the Morgan estate on to rebut some of this, like, equal time.

• 42:28Kelly Weinersmith?

  I mean, okay, so let's take a step back here. He was the advisor for a woman scientist, which was very progressive at the time, I think. Maybe he wasn't being aggressive here, but let's dig in a little bit. So in the obituary, he says that Stevens confirmed McClung's hypothesis. And you might remember that McClung was the guy who was like, X makes males. And he got it exactly wrong. So she didn't confirm his hypothesis.

• 42:55Daniel Whiteson?

  She flipped it on its head.

• 42:56Kelly Weinersmith?

  She flipped it on his head and then did a bunch of extra work to make a much more sound argument. And so here, her contributions are getting sort of obscured. So she's already getting cut out of the conversation. Her contributions are not being attributed correctly in her obituary.

• 43:11Daniel Whiteson?

  But Morgan must have known, right? I mean, obviously, he's like a big man in his field. He was her advisor. He's right there. He understands all this stuff. He must have known what he was doing. Is there any way to see this other than being an intentional obscuring of her name and deflating of her credit?

• 43:25Kelly Weinersmith?

  I think that's probably what happened. Maybe we should get somebody who's like a Morgan expert on, and maybe they can say like, oh, this was during a period where he was drinking too much, and he was just sloppy and something like that. I don't know. Maybe there's a nicer way to look at it. But if I had a PhD student and they died, and I was writing their obituary, and especially- If they were like one of the first women in their field, I feel like I would be very careful about how I wrote that obituary. But so he either was sloppy or he was, you know, being dishonest.

• 43:56Daniel Whiteson?

  But there is a long history of PhD advisors taking credit for graduate student work, and especially when it's a male advisor and a female student. And we have lots of examples of like a man winning the Nobel Prize for work done by their female graduate student. So it's definitely not just biology. And at the time, I think it was very common, unfortunately.

• 44:16Kelly Weinersmith?

  Right. And here's another piece of evidence that sort of builds on, you know, the argument that you just made. Morgan eventually writes a textbook called The Mechanisms of Genetics. And he talks about the work that Stevens and Wilson did, but he doesn't mention, I don't think he mentions either of their names, but he definitely doesn't mention her name. And the way that he wrote it was right before he talked about the contributions that he made to the field. And when you read it, you could be forgiven for thinking that he was on that, you know, whole section, just describing his contribution.

• 44:48Daniel Whiteson?

  Oh, man. Not a fan of Morgan over here.

• 44:52Kelly Weinersmith?

  I'm feeling a little grumpy about Morgan, too. And in 1933, he goes on to get a Nobel Prize, not for the discovery of sex determination, but just for his general work in genetics. And so over time, she's just sort of been forgotten. And so a lot of people forget about both Wilson and Stevens because Morgan became such a hotshot. And a lot of people read this textbook, and I think a lot of them just inferred, oh, okay, Morgan was the one who figured that out, too. And so over time, Stevens has been forgotten, and so has Wilson, relative to Morgan, and Morgan has gotten a bunch of the credit.

• 45:26Daniel Whiteson?

  Think a lot of people don't appreciate how much campaigning and politicking there is in getting a Nobel Prize. Like, it's not just you do a bunch of good science and then you're recognized. It's not some like pure meritocracy. You know, there's a lot of behind the scenes campaigning, like, this person should get the credit, and this person should get the credit, and this is really important. Like, the folks who get the Nobel Prize are the ones who bubble up to the top of that campaign. And every year, there's lots of arguments and discussion, and so wrangling your way into the textbooks and Getting the story told a certain way is definitely a good way to lay the groundwork for later getting the Nobel Prize. So I don't know that that's what Morgan was doing and Nobel Prizes were definitely a newer thing back then. But you know, writing yourself into the history of science is not a new game.

• 46:10Kelly Weinersmith?

  Yeah, unfortunately. And I think often women aren't playing the game or are in a position where they can play the game the same way.

• 46:18Daniel Whiteson?

  I saw this happening like in person. When we discovered that Higgs boson, we knew that somebody was going to get the Nobel Prize for it. And all of a sudden, there were lots of theorists giving talks about their contribution to Higgs theory and the role they played in bringing it to the discovery, because everybody knew it could be shared between three people and Higgs was getting it, but who else was going to get it?

• 46:38Kelly Weinersmith?

  Oh, man.

• 46:38Daniel Whiteson?

  So there's a lot of campaigning, a lot of talks on that topic of the history of those discoveries. And it was very clear what was happening.

• 46:45Kelly Weinersmith?

  I think one day we should talk about your research in particular, but were you one of those people who could have campaigned? Were you around during the Higgs time?

• 46:53Daniel Whiteson?

  I mean, I was on one of the teams, but one question in the air was, were they going to give it to theorists who came up with the idea, or to experimentalists who discovered it, or both? In the end, they gave it just to theorists, which is still sort of controversial. And if they had given it to experimentalists, probably they would have only given it to the heads of the experiments, because the experiments have 5,000 people on it. And you can't give them all the Nobel Prize. That might be one reason why they only gave it to theorists, because how do you decide which experimentalist to give it to? Sort of a fraught question. But yeah, I contributed. I was on those papers. I was there.

• 47:30Kelly Weinersmith?

  Oh, that's exciting, though.

• 47:31Daniel Whiteson?

  I don't think I deserve a Nobel Prize for my contribution. I'm not going to be campaigning for that. But it was fascinating to see the human side of it, to see people actively out there arguing that they deserve the Nobel Prize. And I know that that was influential.

• 47:45Kelly Weinersmith?

  Okay, yeah, that is an interesting insight. I don't think I had on my radar.

• 47:49Daniel Whiteson?

  Yeah.

• 47:50Kelly Weinersmith?

  Okay, that's sort of like the history there, but one of the things that I wanted to talk about briefly is how different this story could have been if it wasn't the case that Y chromosomes are a different shape. And so maybe you would have ended up with the same thing because there were some males who just weren't getting anything. You know, they weren't getting like a paired chromosome at all, and that's how they became males. But Y chromosomes, it turns out over time, they tend to degrade. And so the idea is that most chromosomes often swap material at the beginning of meiosis. And this process of swapping allows you to get rid of genes that have kind of gotten messed up, or they've gotten some bad mutations.

• 48:31Kelly Weinersmith?

  But if you have this part of a chromosome that's now controlling, you know, for example, say it has the code for making testes and for a beard and for a vas deferens, you don't want to be swapping that and risk getting those male-related genes onto the female-related chromosome. So they stop doing that recombination. But that means that anything else that's also on that chromosome that doesn't have anything to do with maleness is now not getting sort of like rejuvenated or removed by this crossing over process. And so over time, those genes, as they get messed up, we think they just sort of like, they fall off because you're not using them anymore. And every once in a while chromosomes sort of lose bits. And sometimes that's a problem, sometimes it's not.

• 49:15Kelly Weinersmith?

  But over time, the Y chromosome tends to degenerate. And you also see this in birds. It's a different chromosome. The males have Z and Z, and the females have Z and W. And that W chromosome is the one that has started to degenerate. So it's also started to lose things. So this observation, like, it seems to me that the reason we started with sex was because of this weird way that these chromosomes sort of change shape over time. And if you hadn't had that clue that these things are different shapes, it would have been much harder to make this observation. And I don't know, that just seemed interesting to me while I was going through this research.

• 49:50Daniel Whiteson?

  Yeah, because it's sort of macroscopic. I mean, you're zooming in, you're using the microscope, but you don't need to look at the actual genome and decode it and like see the structure of DNA to see that there's something different between the X and the Y, even just under a microscope.

• 50:04Kelly Weinersmith?

  And the other thing that's kind of amazing is that they weren't able to figure anything out because the way that whether or not you get an individual that produces sperm or eggs or produces both if they're hermaphrodites, like the various mechanisms through which those things come about are super varied, like reptiles, it does depend on temperature. And then in the birds, they've got like the opposite, like we just talked about, the females are the ones that have the different kinds of chromosomes. And you get some animals that are sequential hermaphrodites. They've got all the genetic code that you need to make either decision and they can switch between what sets of code they're using. And while I was reading about sex determination stuff, there were papers that had titles like

• 50:44Kelly Weinersmith?

  sex chromosome evolution, so many exceptions to the rules. It's like, there are just so many different ways that this all works out. It's kind of amazing. We were able to get a foothold, but we did.

• 50:55Daniel Whiteson?

  Yeah, that's incredible. Everything is messy and it's incredible. You can tell any story. What do we know about the history of this? You're talking about how over time these degrees, what is the history of the evolution of sex in biology? Like, do we know when things went from asexual to having two genders?

• 51:13Kelly Weinersmith?

  So I think that there were a number of different transitions and I am absolutely not an expert in this. This would be a whole topic on its own, I think. But from my reading, what I think I was picking up was that often when you end up with a transition and you end up with offspring that either just have eggs or just make sperm, that usually starts from a hermaphroditic ancestor. So you have the code to do both. And then in some individuals, the set of codes for male traits is turned off. And for some individuals, the set of codes for female traits gets turned off. And you end up producing individuals that can no longer produce both sperm and eggs. They produce only sperm or eggs. And why that would

• 51:53Kelly Weinersmith?

  be beneficial to lose that ability to do both is maybe a little bit unclear. I think one of the leading hypotheses is that there's often not a benefit to reproducing with yourself. So hermaphrodites can often mix their own sperm and eggs to produce offspring. But in an evolutionary sense, the extra genetic diversity that you get by mating with individuals other than yourself has a huge payoff in terms of being able to like stay ahead of parasitic infections and stuff. And so I think there's selective pressure for forcing an individual to mate with other individuals. Whereas if you're hermaphroditic, maybe you're like, oh, it's easier to just mate with me.

• 52:33Kelly Weinersmith?

  We've all been there.

• 52:34Daniel Whiteson?

  I'm gonna stay in. It's Friday night and I'm tired.

• 52:37Kelly Weinersmith?

  That's right. That's right. And that's where the show got not appropriate for kids, maybe.

• 52:43Daniel Whiteson?

  Well, I think about that because we talk about earliest common ancestor and how all life on earth probably has a single ancestor. But, you know, we have gender along the line some point, and we didn't have it early on, which means that at some point it must have, you know, sprung up. And so it's fascinating to me to think about the history of this and where it diverges. And maybe one day we'll have the whole tree of life all the way back through time, and we'll know the answers to all these questions.

• 53:07Kelly Weinersmith?

  Bacteria started with like conjugation, where they'd just be like passing over small chunks of genes. And so there's been a lot of diversity along the way. And without going into too long of a diatribe about definitions, because, to be honest, I'd like to check my definitions before saying them publicly. You know, gender, I think, is often now thought of as being different than just, do you make sperm? Or do you make eggs? It's more about the strategy that you employ as you go through life. And so that's a slightly different thing, just to get our terms correct. And so today, we were specifically talking about gomitic sex. So do you end up with the genetic code to make sperm? Or do you end up with the genetic code to make eggs?

• 53:44Daniel Whiteson?

  All right. So finish the story of Nettie Stevens for us. Tell us about how she tragically passes away.

• 53:49Kelly Weinersmith?

  Yeah, so she finally gets offered that professorship at Bryn Mawr, which she quite clearly earned, because two years before she got this offer, you know, as we mentioned, she was listed in the 1,000 top men of science. So she was, again, one of 18 women. So she was clearly globally known for the work that she was doing. And she had won an award for her work on sex chromosomes. So I think everybody realized that she was making big contributions. But by the time she was ready to start that professorship, she died at age 50 of breast cancer.

• 54:19Daniel Whiteson?

  Oh.

• 54:19Kelly Weinersmith?

  And so who know, I mean, she still had like, a prolific publication record up until that point. I think she had published something like 40 papers. And that was like, you know, what, she got her PhD in 1903?

• 54:30Daniel Whiteson?

  Wow.

• 54:30Kelly Weinersmith?

  And so in maybe a 15 year period, if you include when she was working on her master, she managed to really knock out a bunch of papers, which, to me, is incredible, especially when you consider the tide that she was working against at the time.

• 54:42Daniel Whiteson?

  This is like a Marie Curie type story? Could the work she was doing somehow have contributed to her breast cancer? Were she using like, really dangerous chemicals and this kind of stuff in the lab to do her studies? Or is this just random and Bad luck.

• 54:55Kelly Weinersmith?

  Oh, that's interesting. I didn't come across anyone who was suggesting that the work is what ended up killing her. She was using a lot of different kinds of stains. And so stains make it easier to see the chromosomes as they form and as they separate. I don't know if any of those stains were also carcinogenic, so were also likely to cause cancer. It's possible, but I don't know.

• 55:16Daniel Whiteson?

  As long as we're just listing possibilities, you know, maybe Morgan somehow poisoned her.

• 55:23Daniel Whiteson?

  Let's further besmirch his character.

• 55:26Kelly Weinersmith?

  That's right. I wonder if we're gonna get angry emails, but you know, we'll invite them on the show and they can defend Morgan if they'd like. That would be interesting.

• 55:34Daniel Whiteson?

  Exactly. If you are Thomas Morgan, the fourth or whatever, and you are grumpy at hearing your great, great grandfather's character besmirched, write in and we will clear the air.

• 55:42Kelly Weinersmith?

  Besmirched is a great word. That's not used nearly as often as it should be.

• 55:46Daniel Whiteson?

  It feels sort of very 1900s. I thought it was era appropriate.

• 55:50Kelly Weinersmith?

  Absolutely era appropriate. So anyway, reading about Nettie made me like totally appreciate. I have had difficult sort of steps in my journey. I did end up leaving like a master's lab because of sexual harassment. And so like, it, you know, hasn't been 100% easy, but relative to what she had to go through. Then I've had an easy path. Anyway, it's just kind of a bummer to hear about a woman who was doing amazing work. And, you know, I think it would be reasonable to say that she and Wilson should both jointly be known for this incredible discovery. But, you know, we all think of it as Morgans, which is just a bummer on a lot of levels. So there you go.

• 56:27Daniel Whiteson?

  Here we are pushing gently back against Morgan's politicking to get himself in the top men of science.

• 56:33Kelly Weinersmith?

  There we go. Well, he got a Nobel Prize, so I think he won and we're a little too late. But hopefully y'all will remember the name Nettie Stevens and we'll go ahead and share this story with other people. And Nettie will get the credit she deserves.

• 56:44Daniel Whiteson?

  Congrats, Nettie, on all of your discoveries.

• 56:47Kelly Weinersmith?

  Way to go, Nettie.

• 56:55Kelly Weinersmith?

  Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We would love to hear from you.

• 57:00Daniel Whiteson?

  We really would. We want to know what questions you have about this extraordinary universe.

• 57:06Kelly Weinersmith?

  We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you.

• 57:13Daniel Whiteson?

  We really mean it. We answer every message. Email us at [email protected].

• 57:19Kelly Weinersmith?

  Or you can find us on social media. We have accounts on X, Instagram, Blue Sky, and on all of those platforms you can find us at D and K Universe.

• 57:29Daniel Whiteson?

  Don't be shy. Write to us.

• 57:36Speaker 01

  That sound? That's the National Squash League. Pro teams, the world's best players, in rallies so fast you'll forget to breathe. Season four is in full swing, and every match streams free on YouTube. Big hits, bigger rivalries, and a front row seat from wherever you are. Watch every match for free on YouTube. Search National Squash League and hit subscribe or follow live updates on Instagram at NSL.Sport.

• 58:05Speaker 01

  Wait, I came in for two things. How is this $47? All right, we're gonna need a plan here.

• 58:13Speaker 04

  Just start simple with Bank of America Advantage Safe Balance Banking. No overdraft item fees, no monthly maintenance fee if you're under 25.

• 58:21Speaker 01

  Oh, that's actually really simple.

• 58:24Speaker 04

  Safe balance banking, one less thing to figure out. Learn more at B of A dot com slash simple banking. Terms and conditions apply. Bank of America and a member FDIC.

• 58:34Daniel Whiteson?

  She's been thinking about this sleepover all week, but I think about her food allergies all the time. Fortunately, her doctor prescribed Zolair, omalizumab. It's proven to significantly reduce allergic reactions if a food allergy accident happens. Zolir 150mg is a prescription medication used to treat food allergy in people one year of age and older to reduce allergic reactions due to accidental exposure to one or more foods. While taking Zolir, you should You should continue to avoid all foods to which you are allergic. Don't use if you are allergic to Zolair. Zolair may cause a severe, life-threatening allergic reaction called anaphylaxis. Tell your doctor if you ever had anaphylaxis. Get help right away if you have trouble breathing or if you have swelling of your throat or tongue. Zolair should not be used for the emergency treatment of allergic reactions, including anaphylaxis. Zolair is for maintenance use to reduce allergic reactions, including anaphylaxis,

• 59:18Daniel Whiteson?

  while avoiding food allergens. Serious side effects such as cancer, fever, muscle aches and rash, parasitic infection or hardened circulation problems have been reported. Please see zolair.com for full prescribing information. Ask an allergist about Zolair. This is an advertisement for Zolair paid for by Genentech and Novartis.

• 59:34Speaker 01

  This is Colin Cowherd from the Colin Cowherd Podcast. Buy smart, drive for less, and trade for more. That's Toyota affordability. All starts with a great deal on an off-road ready Tacoma or a half-ton Tundra, two of Toyota's most capable and longest-lasting trucks. Built on a reputation for quality and reliability, Toyota trucks are known for holding their value, which could mean big savings when it's time for your next Toyota. For a great deal today to a great value tomorrow. Shop toyota.com. Toyota, let's go places. This is an iHeart Podcast. Guaranteed Human.