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Nettie Stevens and the Discovery of Sex Chromosomes · Daniel and Kelly’s Extraordinary Universe

0:05
Speaker 1: Hello there, friends. Heads up.
0:07
Speaker 2: As I'm sure you can tell from the title of
0:09
Speaker 2: today's show, we're talking about the birds and the bees again,
0:12
Speaker 2: so keep that in mind as you decide whether or
0:14
Speaker 2: not you want to listen to this with your kids.
0:16
Speaker 1: Also, today, when we.
0:18
Speaker 2: Use the word sex, we're specifically referring to gametic sex,
0:22
Speaker 2: which is to say, we're talking about whether or not
0:24
Speaker 2: a person produces sperm or eggs.
0:26
Speaker 1: Okay, let's get started.
0:29
Speaker 2: About two three hundred years ago, Aristotle postulated that babies
0:34
Speaker 2: come from a mixture of male semen and female blood
0:37
Speaker 2: that mix together in the uterus. To explain how this
0:41
Speaker 2: mixture of fluids turned into either a boy or a
0:44
Speaker 2: girl child, Aristotle pointed to heat. You see, he argued,
0:49
Speaker 2: all embryos start by developing into boys, but if not
0:53
Speaker 2: enough heat is present, then that development will stop and
0:56
Speaker 2: you'll get a girl instead. Five hundred years later, and
0:59
Speaker 2: we still still hadn't made loads of progress. Gallon, a
1:03
Speaker 2: famous Greek physician and philosopher, had a much better sense
1:07
Speaker 2: of human anatomy, but.
1:08
Speaker 1: Was still focused on this heat thing.
1:11
Speaker 2: Ovaries, he argued, were actually just testes that hadn't experienced
1:16
Speaker 2: enough heat to make it through the journey to the
1:18
Speaker 2: outside of the body. By the early nineteen hundreds, we
1:21
Speaker 2: had learned a lot. Gregor Mandel had done his experiments
1:25
Speaker 2: in pea plants, so we knew that traits could be
1:27
Speaker 2: inherited from parents, and we were starting to get an
1:30
Speaker 2: inkling of where the blueprints for that inheritance were being stored.
1:35
Speaker 2: We had seen chromosomes inside of cells, but had not
1:38
Speaker 2: yet tied those chromosomes to the inheritance of specific traits,
1:43
Speaker 2: and this is where Netti Stevens comes in. Nettie, a
1:46
Speaker 2: rare PhD holding woman scientist at the start of the
1:49
Speaker 2: twentieth century, peered into the cells of insects and made
1:53
Speaker 2: an exciting discovery. One pair of chromosomes were different sizes.
1:58
Speaker 2: If you got the smaller chromosome, you were a male,
2:01
Speaker 2: If you got the bigger of the pair, you were
2:03
Speaker 2: a female. Not only had she discovered what went on
2:07
Speaker 2: to be called the X and the Y chromosomes, but
2:09
Speaker 2: this was the first time a particular trait had been
2:12
Speaker 2: tied to a particular chromosome. Today we talk more about
2:16
Speaker 2: Nettie Stevens's life and how she came to make this
2:18
Speaker 2: amazing discovery. Welcome to Daniel and Kelly's Extraordinary Universe.
2:36
Speaker 3: Hi. I'm Daniel. I'm a particle physicist, and I'm very
2:40
Speaker 3: excited to get into the messy questions of biology.
2:43
Speaker 1: I'm Kelly Waider Smith.
2:44
Speaker 2: I'm a biologist, and wow, these questions really can get
2:48
Speaker 2: very messy. There's a lot we haven't figured out here.
2:51
Speaker 2: But I'm excited to talk about the early studying of
2:54
Speaker 2: how we determine if you end up making sperm or eggs.
2:57
Speaker 3: Messy questions, messy answers, messy methid. That's what biology is
3:01
Speaker 3: all about. Getting gooey with it.
3:04
Speaker 1: I like the getting gooey with it part.
3:06
Speaker 2: I don't know about the messy methods, but I'll let
3:09
Speaker 2: that slide.
3:10
Speaker 3: I didn't mean sloppy. I mean that sometimes you literally
3:12
Speaker 3: get gooey. I mean you come home goo all over yourself, right,
3:15
Speaker 3: You're standing in a dumpster full of goo.
3:17
Speaker 1: Yeah.
3:17
Speaker 4: No.
3:18
Speaker 2: There have been a couple instances where I've been like,
3:20
Speaker 2: how did I get fish guts in my hair? And
3:22
Speaker 2: I discovered it later in the day and Zach was
3:25
Speaker 2: just absolutely appalled, and yeah, gud, you marrying a biologist
3:28
Speaker 2: is really gross stuff.
3:31
Speaker 3: I think it's underappreciated out there by the general public.
3:34
Speaker 3: How much the methods and the day to day work
3:37
Speaker 3: decides where you end up in science, because you know, like,
3:40
Speaker 3: you're interested in the questions of biology, but I'm imagining
3:43
Speaker 3: you're not answering the deep questions of biology every day.
3:45
Speaker 3: Mostly you're having fun working with fish guts or whatever,
3:49
Speaker 3: And so you got to enjoy that bit. And you know,
3:51
Speaker 3: I spend most of my time writing programs on the computer,
3:53
Speaker 3: and I enjoy that bit. So it's like, you know,
3:56
Speaker 3: what kind of messying is do you like? Determines what
3:59
Speaker 3: kind of science you do. Probably more than your inherent
4:02
Speaker 3: curiosity about.
4:02
Speaker 2: The universe, absolutely, And I don't necessarily know that. We
4:06
Speaker 2: tell students that enough. Like when I introduced students to
4:09
Speaker 2: working with me when I was a grad student, I
4:10
Speaker 2: mentored like a bunch of undergrads, and I'd be like,
4:12
Speaker 2: look straight up, a bunch of your time is going
4:15
Speaker 2: to be spent in a room that smells awful, like
4:17
Speaker 2: a combination of dead fish and formuline, or like staring
4:21
Speaker 2: and trying to count tiny little items under a microscope.
4:23
Speaker 2: And if you care about the question, you will love
4:26
Speaker 2: every second of that. But if you don't care about
4:28
Speaker 2: the question, you should find a different feel because you're
4:32
Speaker 2: going to be miserable. And some of them dropped out
4:34
Speaker 2: not that long after, but it's good to find out
4:36
Speaker 2: early do you like that kind of stuff or do
4:38
Speaker 2: you not?
4:38
Speaker 3: And sometimes you can care about the question but just
4:40
Speaker 3: not really enjoy the day to day work of it.
4:43
Speaker 3: You know. My first experiences in research were like plasma physics,
4:46
Speaker 3: and I was like, hey, I'm gonna figure out fusion
4:49
Speaker 3: and save the world. And I definitely still care about that,
4:51
Speaker 3: but I find vacuum systems and plasma machines annoying and
4:57
Speaker 3: I did not have a good time that summer. Thank
5:00
Speaker 3: you to those physicists out there who entered me that summer,
5:02
Speaker 3: but I was deeply bored.
5:06
Speaker 2: You really got to try this stuff out when you're
5:07
Speaker 2: an undergrad as much as possible. Like I thought I
5:09
Speaker 2: was gonna love molecular work because it would be like
5:12
Speaker 2: an episode of like CSI. You know, where they're in
5:14
Speaker 2: the like fancy labs and they're pipe heetting to find
5:16
Speaker 2: amazing answers. And I hate pipetting. I'm miserable at it.
5:20
Speaker 2: My hand's hurt, they get tight. I overthink everything doesn't
5:24
Speaker 2: matter how great the music I'm listening to as well,
5:26
Speaker 2: I'm doing it like I cannot get through it, and
5:28
Speaker 2: so I just I stopped doing molecular work.
5:30
Speaker 3: Wait, but do you actually musical montage your way to
5:33
Speaker 3: an answer? Sometimes you're like, I'm gonna jam through this.
5:35
Speaker 3: Let's put on the music and dot dot dot there
5:37
Speaker 3: we are. I love when they do that in TV shows.
5:39
Speaker 2: Someone told me like, look, you're overthinking it. If you
5:42
Speaker 2: just flow, it'll be fine. So pick some music you
5:45
Speaker 2: can flow to. And I lost like a thousand dollars
5:48
Speaker 2: because I messed up a bunch of kids because I have.
5:51
Speaker 1: To do more than just flow. I'm not a person
5:53
Speaker 1: who flows.
5:53
Speaker 5: I guess.
5:55
Speaker 2: But you know, this is a good intro actually, perhaps
5:58
Speaker 2: even accidental, because the woman that we're talking about today,
6:01
Speaker 2: there were maybe fifty or more species of insects where
6:05
Speaker 2: she went through and she like crushed cells, stained cells,
6:08
Speaker 2: and watched different stages as they divided to produce sperm.
6:13
Speaker 2: And I read one of her papers and it had
6:15
Speaker 2: something like two hundred and fifty plates where she had
6:18
Speaker 2: like very carefully drawn what was happening with chromosomes and
6:22
Speaker 2: these various stages that must have taken many, many hours
6:26
Speaker 2: and been incredibly tedious work and counting to track all
6:29
Speaker 2: the chromosomes and how they were matching up with one another,
6:31
Speaker 2: and you know, the patients that it must have taken
6:34
Speaker 2: to even just like extract the game meets out of
6:37
Speaker 2: like a tiny cricket so that you can look at
6:39
Speaker 2: them like that takes a lot of skill. So yeah,
6:42
Speaker 2: she really persisted through a lot of what would have
6:45
Speaker 2: been very boring work to many of us.
6:47
Speaker 1: Maybe she loved it.
6:48
Speaker 2: I don't know, but I looked at the plates and
6:50
Speaker 2: I immediately was like, WHOA.
6:52
Speaker 1: I would have been way too bored to do this.
6:54
Speaker 3: Maybe she was jamming to the hip music of the
6:56
Speaker 3: day the whole time, right, sort of like a lost
6:59
Speaker 3: question in history, what music did famous scientists listen to
7:03
Speaker 3: while they did all their important work?
7:05
Speaker 1: Yeah? Did we have records in the early nineteen hundreds.
7:08
Speaker 5: We must have, right, Yeah, I think we did for.
7:10
Speaker 1: Sure, jamming to some record.
7:12
Speaker 5: Nice.
7:13
Speaker 2: I like the idea that that's what was happening. Too
7:15
Speaker 2: bad she couldn't listen to our podcast.
7:18
Speaker 3: Somebody out there write a book about the history of
7:21
Speaker 3: music listened to by scientists.
7:24
Speaker 1: I don't know.
7:24
Speaker 2: If that sound career advice, I don't know how big
7:27
Speaker 2: the audience is for that book.
7:29
Speaker 3: I want to read that book, so I don't care
7:30
Speaker 3: if somebody out there write it.
7:32
Speaker 1: Okay, great, sounds good.
7:34
Speaker 3: Today we're not talking about music, but we are talking
7:36
Speaker 3: about pioneering scientists who made incredible discoveries that influence the
7:40
Speaker 3: way we think about big, important questions in our life.
7:44
Speaker 3: In this case, big important, messy biological questions.
7:48
Speaker 2: Yes, and we're specifically focusing on scientists that most people
7:52
Speaker 2: have never heard of, despite the fact that they made
7:55
Speaker 2: absolutely profound discoveries about the way that life works. And
7:58
Speaker 2: so we pose to our our audience the question what
8:02
Speaker 2: was Nettie Stevens's big biological discovery? And if you want
8:07
Speaker 2: to answer our questions, contact us at questions at Danielankelly
8:11
Speaker 2: dot org and we'll add you to the list and
8:14
Speaker 2: we'll send you our question before an episode and you
8:16
Speaker 2: can give us your best guess. All right, let's hear
8:18
Speaker 2: what our audience came up.
8:19
Speaker 1: With this time.
8:20
Speaker 4: Nettie Stephens discovered that as long as radioactivity is negligent
8:27
Speaker 4: a cell, your mechanism will be able to achieve spasis
8:31
Speaker 4: for a nominal period or duration of time.
8:35
Speaker 5: I'll be honest, I've never heard of Nettie Stevens.
8:39
Speaker 3: Well, this one's short. I have no idea.
8:43
Speaker 6: Did Nettie Stevens invent the Nettie pot that allows you
8:47
Speaker 6: to irrigate the biological war zone happening in your sinus
8:51
Speaker 6: cavity as long as you hold your head at the
8:53
Speaker 6: proper angle. Otherwise you end up with a salty, slimy
8:58
Speaker 6: soup for lunch.
9:00
Speaker 7: My completely uninspired guess is that she discovered that the
9:08
Speaker 7: Lockness monster is real.
9:12
Speaker 2: All right, So to be clear, despite the profound confidence
9:16
Speaker 2: that we're hearing in that very first explanation, that is
9:19
Speaker 2: not correct, is.
9:21
Speaker 3: That totally manufactured or is that somebody else?
9:23
Speaker 4: Yeah?
9:23
Speaker 2: No, no, that's totally manufactured hero and made some sort
9:26
Speaker 2: of joke about like, you know, the more confident you
9:28
Speaker 2: sound something like that.
9:29
Speaker 3: So that sounds like a chat GEPT answer, right, total
9:32
Speaker 3: confidence and total nonsense.
9:34
Speaker 2: Sometimes chat GPT gets it right, but yes, often it's hallucinating,
9:37
Speaker 2: which this listener was perhaps also doing. She's not associated
9:41
Speaker 2: with the Nettie Pot. And then we had two listeners
9:44
Speaker 2: who had never heard of her.
9:46
Speaker 3: Well, it sounds like there's a lot of folks out
9:47
Speaker 3: there who need to know more about Nettie Stevens and
9:50
Speaker 3: what she contributed to our understanding of the biological world.
9:53
Speaker 3: So let's go, let's find out. Let's hear all about
9:57
Speaker 3: Nettie Stephens. So Kellie telling us who was Attie Stevens.
10:00
Speaker 2: And I'll do my best to sound confidence so that
10:02
Speaker 2: even if I'm wrong, everyone will believe it.
10:05
Speaker 3: Well, I'm pretty sure you're not an AI. I mean,
10:07
Speaker 3: I've known you long enough. I think I would have
10:09
Speaker 3: figured it out by now.
10:10
Speaker 2: All right, AI is getting pretty good, all right, So
10:14
Speaker 2: Nettie and Maria Stevenson. She was born in eighteen sixty
10:17
Speaker 2: one in Vermont, and she was born to like a
10:19
Speaker 2: middle class family, and unfortunately her mom died.
10:22
Speaker 1: When she was pretty young.
10:23
Speaker 2: But she was lucky that she had a father who
10:26
Speaker 2: really wanted to invest in his daughter's education, and she
10:29
Speaker 2: also had a sister, and so he sent them to school.
10:32
Speaker 2: They went to west Ford Academy and she studied to
10:35
Speaker 2: be a teacher.
10:36
Speaker 3: Is this something that was unusual at the time, Like,
10:38
Speaker 3: did most women go to school? Did most folks living
10:41
Speaker 3: in middle class Vermont go to school? Or was it
10:44
Speaker 3: unusual for them to go.
10:45
Speaker 2: It was pretty unusual. So training to be a teacher
10:48
Speaker 2: wasn't super unusual. Training to be a scientist definitely was,
10:52
Speaker 2: but it was still fairly unusual. And so she leveraged
10:56
Speaker 2: this early education as a teacher so that through various
11:00
Speaker 2: points in her life she could teach for a while
11:01
Speaker 2: to save up money so that she could afford to
11:04
Speaker 2: follow her dream, which was to become a scientist. And
11:07
Speaker 2: so she would teach for a while save up money,
11:09
Speaker 2: and at one point, after saving her money, in eighteen
11:12
Speaker 2: ninety six, she started at a new school that you know,
11:16
Speaker 2: maybe you hadn't heard of, called Leland Stanford Junior University.
11:20
Speaker 2: It ends up becoming Stanford and she gets a bachelor's
11:24
Speaker 2: and a master's there.
11:25
Speaker 3: Wow, And how many women are attending Stanford in the
11:28
Speaker 3: late eighteen hundreds.
11:29
Speaker 1: Not many.
11:30
Speaker 2: I don't know the exact number, but there were not many.
11:33
Speaker 2: And as you'll see, like at one point when she
11:35
Speaker 2: gets recognized for her amazing contributions, she's on a list
11:39
Speaker 2: of the top one thousand men in science. Oh so,
11:46
Speaker 2: and she was one of eighteen women on that list.
11:48
Speaker 2: So to sort of give you some sense of how
11:51
Speaker 2: many famous women's scientists there were at the time, there
11:54
Speaker 2: were eighteen women who broke into this list of one thousand,
11:56
Speaker 2: and this was towards the end of her career.
11:58
Speaker 3: And did she also get married, didn't have a family,
12:01
Speaker 3: or did she have to choose between those paths.
12:03
Speaker 2: So I wasn't able to find a lot of personal
12:05
Speaker 2: information about Nettie. I haven't been able to find a
12:08
Speaker 2: biography that people wrote about her, the Encyclopedia Britannica, Wikipedia,
12:12
Speaker 2: everywhere you go, they pretty much say the same things.
12:14
Speaker 2: I found a couple scientific papers talking about her early
12:17
Speaker 2: life and contributions, and they all just sort of like
12:20
Speaker 2: list off the same facts.
12:22
Speaker 3: Sounds like someone who needs to do a deep dive
12:23
Speaker 3: and write a book about Nettie Stevens. We're like both
12:25
Speaker 3: projects out the wazoo on this episode today.
12:28
Speaker 2: Absolutely, and she was connecting with a lot of major
12:30
Speaker 2: players in the field at the time, and so I
12:32
Speaker 2: think there'd be a lot of interesting information to go on.
12:34
Speaker 2: And maybe like the letters of her advisor, who was
12:39
Speaker 2: ended up being a famous scientist, we'll talk about him,
12:41
Speaker 2: like might have mentioned enough where he could get some
12:42
Speaker 2: more personal details. But anyway, there weren't a lot of
12:44
Speaker 2: personal details, but No, she did not end up getting
12:47
Speaker 2: married or having kids, and she ended up being buried
12:50
Speaker 2: with her dad and her sister. So science was her
12:53
Speaker 2: life as far as I was.
12:54
Speaker 1: Able to tell.
12:55
Speaker 2: Married to biology, maybe she had some great hobbies and
12:57
Speaker 2: had some really cute dogs, but we don't really know.
13:01
Speaker 3: Well, it sounds like she had a really fulfilling and
13:02
Speaker 3: satisfying life, So go Nettie.
13:04
Speaker 1: Yes, no, absolutely so.
13:06
Speaker 2: Early in her career she identifies two new species of ciliates,
13:10
Speaker 2: but she ends up wanting to study more sort of
13:12
Speaker 2: genetic based stuff.
13:13
Speaker 3: What's a ciliat?
13:14
Speaker 2: Sorry, these are tiny little u carryouts and ciliats are
13:17
Speaker 2: like little hairs that they have on the outside of them,
13:19
Speaker 2: and so these hairs sort of are moving frantically to
13:23
Speaker 2: get them from place to place, and they are teeny
13:25
Speaker 2: tiny little things. And she's managed to find two new species.
13:28
Speaker 3: And how exciting is that to find two new species
13:30
Speaker 3: of silias? Is that the kind of thing that we
13:32
Speaker 3: do every day because there's the zillions of them like beetles,
13:35
Speaker 3: or is it like a big breakthrough or what do
13:37
Speaker 3: you learn when you name two new species of ciliates.
13:39
Speaker 2: There's a lot of cillios to name a new species,
13:43
Speaker 2: especially today, requires a lot of like precise measurements and
13:46
Speaker 2: studying the ecology of the animal and coming up with
13:49
Speaker 2: an argument about why it's different than anything that's been
13:51
Speaker 2: identified before. So it's really good practice for very careful
13:55
Speaker 2: measurements of different sort of like organ parts and getting
13:58
Speaker 2: really good at sort of like drawing things and tracking
14:01
Speaker 2: sizes and having a good eye for what's different between things.
14:05
Speaker 2: And so that was probably a really great skill for her.
14:07
Speaker 2: But I don't think anyone's ever won a Nobel for
14:10
Speaker 2: identifying a new ciliot.
14:11
Speaker 3: Unfortunately, it would be pretty silly to win a Nobel
14:14
Speaker 3: Prize for ciliots.
14:16
Speaker 1: I don't know about.
14:17
Speaker 2: Oh silly, it's ah, maybe I am an ai not
14:21
Speaker 2: getting the jokes.
14:23
Speaker 3: Well, you know, I often am criticizing biology as like
14:26
Speaker 3: just being botany, because I feel like the interesting bit
14:29
Speaker 3: of science is not let's go out and describe what
14:32
Speaker 3: we see in the world, But it's the part where
14:34
Speaker 3: we harmonize it, We put it in context, we understand
14:37
Speaker 3: the differences, the distinctions, what those trends mean, right, not
14:40
Speaker 3: just like, hey, here's a list of all the different
14:42
Speaker 3: silly bits in the world, and we call them ciliots,
14:45
Speaker 3: you know, And we do this in particle physics also, right,
14:47
Speaker 3: we have all these particles. We don't understand them, but
14:49
Speaker 3: we want to or we're asking those questions like why
14:52
Speaker 3: do we have an electron amuant and a taw. So
14:54
Speaker 3: when somebody makes a new species, is it always interesting
14:58
Speaker 3: just having seen it or is it only because it
15:00
Speaker 3: raises these questions about evolution and the context in history.
15:04
Speaker 1: I think it's both.
15:05
Speaker 2: And actually I feel like right now, especially in my field,
15:08
Speaker 2: it's underappreciated when you describe a new species because there
15:11
Speaker 2: is such an emphasis on like how does this fit
15:14
Speaker 2: into bigger theories?
15:15
Speaker 1: And like that's the kind of stuff that gets to
15:16
Speaker 1: an NSF grant.
15:17
Speaker 2: And to be honest, I feel like we are racing
15:20
Speaker 2: way ahead on the theory and not stopping to do
15:23
Speaker 2: enough cataloging so that you actually have the data you
15:25
Speaker 2: need to test these theories.
15:27
Speaker 1: We should have a.
15:27
Speaker 2: Whole episode on that. But we're getting off topic, all right.
15:30
Speaker 2: I would argue that both of those things, the cataloging
15:32
Speaker 2: and the big theories, you can't do one well without
15:34
Speaker 2: the other.
15:35
Speaker 1: They're built critical.
15:36
Speaker 3: You need botany and philosophy to come together in harmony.
15:39
Speaker 3: All right, But let's get back on track with Nettie.
15:41
Speaker 3: So she's discovered two new silly kinds of sili. It's
15:44
Speaker 3: what happens to her next.
15:46
Speaker 2: She saves up some money again, and then she ends
15:48
Speaker 2: up going to get her PhD at Brinmar.
15:50
Speaker 3: And she's saving up money because she's paying to do this,
15:53
Speaker 3: so she's like paying for her education.
15:55
Speaker 2: I think she probably had to pay for things like
15:57
Speaker 2: her housing. I don't know what kind of fellowship they
15:59
Speaker 2: offered her, but I do know that when she got there,
16:01
Speaker 2: she was an absolute rock star. And she got the
16:04
Speaker 2: Brandmar President's European Fellowship, so she got to go to
16:07
Speaker 2: Naples to work with this famous guy doing genetics work
16:11
Speaker 2: at the time. So she was like an absolute rock star.
16:14
Speaker 2: And she wraps up her PhD. And this is when
16:16
Speaker 2: stuff really starts going. So she starts getting interested in
16:19
Speaker 2: whether or not chromosomes are what determines if you end
16:24
Speaker 2: up making sperm or eggs, and she gets a big
16:27
Speaker 2: grant to answer this question. And when we come back
16:29
Speaker 2: from the break, we're going to talk about what the
16:31
Speaker 2: prevailing theories at the time are for what gives you
16:33
Speaker 2: boys and what gives you girls.
16:51
Speaker 1: All right, we're back.
16:52
Speaker 2: So let's take a bit of a historical perspective to
16:55
Speaker 2: figure out where we are. After Nettie Stevens has finished
16:58
Speaker 2: her PhD. So she finished her pe in nineteen oh three,
17:01
Speaker 2: so over two hundred years earlier. Anton von Layan Hook
17:06
Speaker 2: had looked at his sperm underneath the microscope and the
17:08
Speaker 2: sperm of dogs also, so we knew sperms existed for
17:11
Speaker 2: over two hundred years.
17:12
Speaker 3: And Lewin Hook is the guy who discovered the cell originally, right,
17:15
Speaker 3: he's like first dude to look in detail at microscopic biology.
17:20
Speaker 2: Von Leaywin Hook was not the first one to see cells.
17:22
Speaker 2: That was Robert Hook. Von Luayne Hook saw little organisms
17:26
Speaker 2: in pond water. He called them animacules, and he also
17:30
Speaker 2: did a lot of exploring for little animacules in on
17:34
Speaker 2: and from his body. So he was the first one
17:37
Speaker 2: to observe sperm.
17:38
Speaker 3: I love the word animacules.
17:40
Speaker 1: That's awesome it is, and it's also cute and I.
17:43
Speaker 3: Like kees exactly like little tiny animals. How nice? Yeah,
17:48
Speaker 3: So was he surprised to discover like wiggly things in
17:51
Speaker 3: his semen?
17:51
Speaker 4: Like?
17:52
Speaker 3: Is this a big shock to him? Or was he
17:54
Speaker 3: looking for that.
17:55
Speaker 2: Yeah, I think he was a little bit surprised, and
17:57
Speaker 2: there was some question about whether or not that was
17:59
Speaker 2: like cantam nation and the like fluid around the sperm
18:03
Speaker 2: is what was actually important for making babies, And so
18:07
Speaker 2: I think he was surprised and he wrote it up,
18:08
Speaker 2: sent it to the Royal Society and turned out, yeah,
18:12
Speaker 2: that those sperm are important in making.
18:14
Speaker 5: Babies, all right, cool, And.
18:15
Speaker 2: Then about one hundred and fifty years later we have
18:18
Speaker 2: the first description of mammalian eggs. So for a while,
18:22
Speaker 2: actually we use these phrases male sperm and female sperm,
18:25
Speaker 2: and the idea was that out of the ovaries came
18:28
Speaker 2: sort of the female equivalent of sperm. And it took
18:31
Speaker 2: a while before someone actually observed eggs. I think they
18:34
Speaker 2: had dissected a rabbit to see eggs for the first time.
18:37
Speaker 2: But so by about eighteen twenty five, we have seen eggs,
18:40
Speaker 2: we have seen sperm.
18:42
Speaker 3: And how do you know what an egg is that
18:43
Speaker 3: he recognized it, say like, oh, this is obviously the
18:46
Speaker 3: counterpart to the sperm, like it's in just another cell
18:49
Speaker 3: in the body.
18:49
Speaker 2: Yeah, that's a good question, because it would be another
18:51
Speaker 2: fifty years before we saw the fusion of sperm and
18:54
Speaker 2: egg to come together to produce like an embryo. But
18:58
Speaker 2: I think that it was a series of experiments that
19:01
Speaker 2: were done on rabbits where they were sort of dissected
19:03
Speaker 2: at different times, and they observed like the same kind
19:06
Speaker 2: of cell sort of moving out of the ovaries and
19:08
Speaker 2: into the uterus. And I think that that's what they
19:11
Speaker 2: when they were like, Okay, we don't have female semen.
19:13
Speaker 2: We've got this little thing that like makes a journey
19:16
Speaker 2: from the ovary into the uterus.
19:18
Speaker 1: And I think that they had seen bird.
19:20
Speaker 2: Eggs, which sort of gave them like this egg sort
19:23
Speaker 2: of idea. I believe that that's the history of how
19:26
Speaker 2: we observed eggs.
19:27
Speaker 3: And that sort of the broader context, Like people are
19:30
Speaker 3: wondering how sex works and how you end up with
19:33
Speaker 3: boys or girls, and there's already this prevailing concept that
19:36
Speaker 3: it could be determined by something like microscopic You know,
19:39
Speaker 3: where are we in like relation to germ theory in
19:41
Speaker 3: this idea that like there are tiny invisible bits in
19:44
Speaker 3: biology that could have big macroscopic impact.
19:47
Speaker 2: So I think the prevailing theory is that, like, yes,
19:50
Speaker 2: these things can come together and they can be important
19:52
Speaker 2: in the production of offspring, but how does that end
19:56
Speaker 2: up as a boy or a girl is still an
19:58
Speaker 2: open question, and so one of the theories from like
20:02
Speaker 2: seventeen forty eight, there was this book by a French
20:05
Speaker 2: anatomist whose last name was Kuteau, and the book was
20:08
Speaker 2: called The Art of Having Boys, because obviously that's.
20:12
Speaker 1: What you'd want to be doing.
20:13
Speaker 2: And the idea was that sex organs come in pairs,
20:16
Speaker 2: so males have two testes, females have two ovaries, and
20:20
Speaker 2: so it must be that one testee is important for
20:24
Speaker 2: making males and one makes females, and they hang at
20:27
Speaker 2: different heights, and so you should be able to figure
20:29
Speaker 2: out which one makes boys and which one makes girls.
20:32
Speaker 3: And so this is also very logical and also off base.
20:37
Speaker 2: Well that this book actually went through four editions, which
20:40
Speaker 2: is more editions than my book has gone through, so
20:42
Speaker 2: this was apparently better than anything I've done in my life.
20:45
Speaker 2: So he actually proposed that if you want boys, you
20:48
Speaker 2: could figure out which testes makes boys and which one
20:51
Speaker 2: makes girls, and you could remove the one that makes
20:53
Speaker 2: girls to make sure.
20:53
Speaker 1: You make boys.
20:55
Speaker 2: But for the more timid he notes that since there's
20:58
Speaker 2: one ovary that makes girls, and one ovary that makes boys.
21:01
Speaker 2: You could instead just have the woman lay on one side,
21:04
Speaker 2: so gravity will send the sperm to the ovary to
21:07
Speaker 2: get the child you want.
21:08
Speaker 1: Wow, So none of this works. Don't trust best selling authors.
21:13
Speaker 3: That's a more general, long standing lesson. Yeah, so people
21:16
Speaker 3: understand it's something microscopic, but we want to understand the
21:19
Speaker 3: more detailed mechanism, and that's what people are using microscopes
21:22
Speaker 3: and dissecting stuff.
21:23
Speaker 2: Yes, right, And while we're on the topic of what
21:26
Speaker 2: ends up giving you boy and girl babies as classically defined.
21:30
Speaker 2: At the time, nutrition was another popular idea, and so
21:33
Speaker 2: the idea was that if you are under fed, you'll
21:36
Speaker 2: produce boys. And I think the argument there is that
21:39
Speaker 2: sperm they're like smaller and they're chasing to get to
21:42
Speaker 2: the bigger eggs and so if you're not eating enough,
21:46
Speaker 2: you produce these smaller sperm things.
21:48
Speaker 1: And it's confusing.
21:50
Speaker 3: Man. If we had social media back then, there would
21:51
Speaker 3: been lots of crazy influencers telling people how to have
21:54
Speaker 3: boys or girls.
21:55
Speaker 1: Oh my gosh, so many.
21:56
Speaker 2: But you know, to be fair, so like in the
21:58
Speaker 2: animal Kingdom, whether are not you get an individual who
22:01
Speaker 2: produces eggs, an individual who produces sperm or an individual
22:04
Speaker 2: who produces both. So hermaphrodites of different types is actually
22:09
Speaker 2: very complicated, and so this idea for nutrition wasn't completely crazy.
22:14
Speaker 2: So like they had taken a bunch of sheep and
22:16
Speaker 2: they malnourished some and they overfed others, and they ended
22:20
Speaker 2: up with sixty percent female offspring and forty percent males.
22:25
Speaker 2: And then there were some what they called lower vertebrates
22:28
Speaker 2: where they did these experiments and the effects were even
22:31
Speaker 2: more pronounced.
22:31
Speaker 1: And so there are some species where nutrition sort of.
22:34
Speaker 2: Plays a role in whether or not you're more likely
22:36
Speaker 2: to get offspring that make sperm or offspring that make eggs.
22:39
Speaker 2: And so they had made some observations that were consistent
22:41
Speaker 2: with this idea, but it just turns out that's not
22:43
Speaker 2: how most things work, and of course that's not how
22:45
Speaker 2: humans work.
22:46
Speaker 3: All right, So Lowen Hook sees the sperm people discover eggs.
22:50
Speaker 3: Kutou writes a nonsense book about the art of having boys.
22:54
Speaker 3: It's understood to be very complicated. How did Nettie get involved,
22:58
Speaker 3: what was her interest and what did she.
22:59
Speaker 2: Cant Taking a very slight step back in like eighteen
23:03
Speaker 2: sixty five, Gregor Mendel did his pa experiments that you
23:06
Speaker 2: might have learned about in high school, but it was
23:07
Speaker 2: a long time ago for me at least. So essentially,
23:10
Speaker 2: he did all these crosses of pea experiments, and he
23:12
Speaker 2: discovered that the traits in the like BABP plants were
23:16
Speaker 2: being inherited from the parents, but it wasn't clear what
23:20
Speaker 2: material was passing that information from one generation to another.
23:24
Speaker 2: So he made these amazing contributions to science which were
23:28
Speaker 2: promptly forgotten about, and nobody looked at it like I
23:31
Speaker 2: think literally, so a long time ago, when books would
23:34
Speaker 2: be printed, sometimes you'd have to separate pages with like
23:37
Speaker 2: a little knife because of the way they were printed.
23:39
Speaker 2: And so Darwin had Mendel's book on his bookshelf. But
23:44
Speaker 2: the story, and maybe this is apocryphal, but I've been
23:47
Speaker 2: told it like five or six times, so I'm gonna
23:48
Speaker 2: go ahead and share it, was that he hadn't actually
23:51
Speaker 2: opened up the pages in his book where he would
23:54
Speaker 2: have learned about this inheritance stuff, So he could have
23:56
Speaker 2: learned about it, but he didn't. But anyway, okay, Gregor
23:59
Speaker 2: Mendel does this inhered and stuff. Everybody forgets about it
24:02
Speaker 2: around eighteen seventy, we first see genetic material, so it's
24:05
Speaker 2: called nucleon. We don't really know what it does, but
24:09
Speaker 2: we've now seen genetic material.
24:11
Speaker 3: Meaning that we've gone now insize cell. So not just
24:14
Speaker 3: like here's a sperm, but we're like digging into the
24:16
Speaker 3: cell and finding the bits that carry that information.
24:20
Speaker 1: Yes, yep, exactly.
24:21
Speaker 2: But then by the early twentieth century, so around nineteen hundred,
24:24
Speaker 2: Mendel is rediscovered by a bunch of scientists and we're like,
24:28
Speaker 2: oh my gosh, okay, traits are inherited from parents. We
24:30
Speaker 2: have good evidence for that, but what are the blueprints
24:33
Speaker 2: that are transmitting this information? And so now you can
24:36
Speaker 2: combine the fact that you've seen this stuff inside of
24:39
Speaker 2: cells and that feels like maybe that's the stuff that
24:41
Speaker 2: transmits the information. And so now people are starting to
24:44
Speaker 2: dig into that. And so this is the scientific background
24:48
Speaker 2: of where Nettie Stevens jumps in. So in eighteen ninety one,
24:52
Speaker 2: Herman Vaughn Hanking, he's studying chromosomes. He's noticing that they
24:56
Speaker 2: almost always pair up, but he notices that there's this
24:58
Speaker 2: one thing that doesn't hair up, and he calls it
25:01
Speaker 2: the X element. But he doesn't know what it does.
25:04
Speaker 2: And this is before the nineteen hundreds when Gregor Mandel
25:08
Speaker 2: had been sort of rediscovered and his works had been rediscovered,
25:11
Speaker 2: so people at that time weren't really trying to connect
25:14
Speaker 2: the stuff that was in the cell to traits that
25:16
Speaker 2: got inherited across generations. So he's just like, oh, there's
25:19
Speaker 2: this thing and it kind of acts different than the
25:21
Speaker 2: other stuff, and he calls it the X element. About
25:24
Speaker 2: ten years later, Clarence McClung notices the same thing, and
25:28
Speaker 2: he changes from the like super X many awesome sounding
25:31
Speaker 2: X element to the accessory chromosome, which is a boring
25:37
Speaker 2: which is so boring.
25:39
Speaker 3: It still has X in the title, right, eccessory chromosome.
25:43
Speaker 1: I think we got to talk about your spelling.
25:50
Speaker 2: But in nineteen oh two he notices this accessory chromosome
25:55
Speaker 2: and he says, okay, look, it doesn't seem like all
25:58
Speaker 2: of the sperm cell are getting it, and so maybe
26:02
Speaker 2: this is important in determining who becomes a male and
26:05
Speaker 2: who becomes a female, because that's the most obvious difference
26:07
Speaker 2: between the organisms that he's studying, his male and female traits.
26:11
Speaker 1: And he postulates incorrectly.
26:14
Speaker 2: That the males are the one who gets this extra
26:18
Speaker 2: accessory chromosome. It increases the metabolism of the organism who
26:22
Speaker 2: gets it, and that's how you get males.
26:25
Speaker 3: So he's right on the edge of discovering this, but
26:27
Speaker 3: he gets it like basically exactly backwards.
26:30
Speaker 1: That's right.
26:31
Speaker 2: But you know, I think so often when you study
26:33
Speaker 2: the story of how a scientific discovery comes along, what
26:36
Speaker 2: you want is like one person who out of the
26:38
Speaker 2: blue came up with the idea, because.
26:40
Speaker 1: That makes for a better story.
26:41
Speaker 2: But no, this just like almost all science, is like
26:44
Speaker 2: a community sort of moving towards an answer, and there's
26:47
Speaker 2: multiple players sort of along the journey. So McClung is
26:50
Speaker 2: getting really close, but he gets it in reverse.
26:54
Speaker 3: I think that's almost always the case. Like if you
26:56
Speaker 3: go back and understand like Einstein's work, you see how
26:59
Speaker 3: many pieces he has pulled together from other folks, and
27:02
Speaker 3: you see other people publishing the same idea like weeks
27:05
Speaker 3: after him, done independently. Like it's almost always the case
27:09
Speaker 3: that science flows as a wave and there's somebody surfing
27:12
Speaker 3: at the very edge of it, and we like to
27:14
Speaker 3: write those dramatic stories. It's like single genius in the
27:16
Speaker 3: dark with a candle, you know, and a blanket to
27:19
Speaker 3: ward off the Scottish cold. But more often it's a
27:22
Speaker 3: big community effort.
27:23
Speaker 1: Yeah.
27:23
Speaker 2: I think that wave is often made of many, many
27:25
Speaker 2: colleagues who are holding that person up and pushing them forward.
27:28
Speaker 2: It's not just one person. And that ends up being
27:31
Speaker 2: the case here too. So Nettie Stevens after her PhD,
27:35
Speaker 2: she got this big grant to study how those chromosomes
27:38
Speaker 2: might determine the sex of individuals, and in nineteen oh
27:41
Speaker 2: five she publishes her seminal study, Studies in Spermatogenesis. And
27:47
Speaker 2: what she did was she looked at a bunch of
27:48
Speaker 2: different kinds of insects. So she looked at a species
27:50
Speaker 2: of termites, a species of sand crickets, croton bugs, and
27:55
Speaker 2: crucially she looks at meal worm beetles and what she
27:58
Speaker 2: does for each of them. And this is what we
27:59
Speaker 2: were talking about earlier. I said there were two hundred
28:01
Speaker 2: plates where it was meticulously documenting where the chromosomes were
28:05
Speaker 2: going over time and what was happening. And she was
28:07
Speaker 2: counting all the chromosomes. So she notes accessory chromosomes in
28:11
Speaker 2: some of the species that she's looking at. But when
28:13
Speaker 2: she gets to the mealworm beetle, She's like, Okay, when
28:17
Speaker 2: you pair up the chromosomes, there is a pair where
28:19
Speaker 2: you have a big chromosome and a little chromosome. And
28:23
Speaker 2: I think that the individuals who get the little chromosome
28:26
Speaker 2: become the males, and the ones that get the big
28:28
Speaker 2: chromosome become the females. And part of why I think
28:31
Speaker 2: that is because when you look inside the adult cells,
28:33
Speaker 2: forget the sperm, let's look at adults. In those adults,
28:36
Speaker 2: the males have that little chromosome and the females have
28:39
Speaker 2: that big chromosome. So that must be the thing that
28:41
Speaker 2: determines sex. And getting that big X that makes you
28:45
Speaker 2: a female. McClung said, it made you a male, but
28:47
Speaker 2: that makes you a female.
28:48
Speaker 3: And is this what Needdie was studying? What she was
28:51
Speaker 3: like out to figure out? How did she get interested
28:53
Speaker 3: in this question?
28:54
Speaker 1: This was what she set out to discover.
28:56
Speaker 2: I think you know she was a person who was
28:58
Speaker 2: good at looking at tiny little things and making measurements
29:02
Speaker 2: and observations on tiny little things, and she was getting
29:05
Speaker 2: interested in genetics because this field was burgeoning and becoming exciting.
29:08
Speaker 2: While she was working on her PhD. So like, while
29:11
Speaker 2: she was working on her PhD, this was the time
29:13
Speaker 2: when Mendel's rules were being rediscovered concurrent with our discovery
29:18
Speaker 2: of some genetic material. So trying to tie those things
29:21
Speaker 2: together became something she was interested in. And actually her
29:24
Speaker 2: PhD advisor ended up becoming a gigantic name. He's considered
29:28
Speaker 2: one of the fathers of modern genetics. So he ended
29:31
Speaker 2: up ultimately establishing like drosophla as a major organism used
29:36
Speaker 2: for lab work, and he connected a bunch of different
29:38
Speaker 2: chromosomes to different traits, and so I think it was
29:41
Speaker 2: sort of like in the air, and she came from
29:43
Speaker 2: a lab that was sort of interested in these sorts
29:45
Speaker 2: of questions.
29:46
Speaker 3: Well, so this must have been a huge discovery for her,
29:49
Speaker 3: like to see such a clear answer to this question
29:52
Speaker 3: that's on everybody's minds.
29:54
Speaker 2: Yeah, okay, that's totally true. It should have been a
29:56
Speaker 2: super big deal. It happened concurrent though, in this the
30:00
Speaker 2: same year that she published this, Edmund Beecher Wilson, who
30:04
Speaker 2: was another geneticist who's farther along in his career. He
30:07
Speaker 2: was looking at a different insects species. He was looking
30:11
Speaker 2: at the accessory chromosomes and he also said, hey, accessory chromosomes.
30:16
Speaker 2: These are what makes males and females, and the female
30:18
Speaker 2: is the one.
30:18
Speaker 1: That gets the X.
30:20
Speaker 2: So he came up with the same discovery in the
30:23
Speaker 2: same year. His paper got published a few months before hers.
30:28
Speaker 2: Oh no, I know, but they had been talking to
30:31
Speaker 2: each other, and so he references in an updated version
30:34
Speaker 2: of his paper. He references that, like, hey, Neddie Stevens
30:38
Speaker 2: found the same thing, and actually she found this little
30:40
Speaker 2: why thing, And so I believe they had been looking
30:43
Speaker 2: at insects that had slightly different systems for sex determination.
30:46
Speaker 2: So in some cases males had the Y and in
30:49
Speaker 2: some cases males were made by simply not getting anything.
30:53
Speaker 2: So the females got the extra X and the males
30:55
Speaker 2: got nothing. They were just sort of missing that information.
30:58
Speaker 2: And so they had both come up with this at
30:59
Speaker 2: the same time. They were both it sounds to me
31:02
Speaker 2: like respectfully communicating their results to one another, and they
31:06
Speaker 2: just happened to submit And his came out a little
31:08
Speaker 2: bit before hers, but she's largely credited with being much clearer.
31:12
Speaker 2: And she went ahead and took that extra step and
31:15
Speaker 2: looked in the cells of the adults and was like, okay,
31:18
Speaker 2: this thing that we're seeing in the sperm plays out
31:20
Speaker 2: in the adults. The adult males have the Y and
31:22
Speaker 2: the adult females have the X. But I don't actually
31:25
Speaker 2: feel like it's worth trying to decide, like whose words
31:28
Speaker 2: were more firm than another, Like, I know we want
31:31
Speaker 2: one person to be out ahead of the other, but
31:33
Speaker 2: like they both did really good work, yeah, around the
31:37
Speaker 2: same time, and this is how science works, and you know,
31:40
Speaker 2: joint credit seems reasonable to me.
31:42
Speaker 3: To me, the issue of these priority disputes is not
31:45
Speaker 3: who sent in their paper first or who took longer
31:48
Speaker 3: in review and got it published first. It's just like,
31:51
Speaker 3: was the work independent? Because if you read somebody else's
31:54
Speaker 3: paper and then publish based on that, then you shouldn't
31:57
Speaker 3: get credit for their discovery because you're building on top
31:59
Speaker 3: of it. But if you figured it out in your
32:01
Speaker 3: own dank Scottish laboratory, you know, then you figured it
32:05
Speaker 3: out on your own and if it's in parallel, you
32:06
Speaker 3: should both get credit. It doesn't matter if you published
32:09
Speaker 3: six months earlier or six months later. It's an independent
32:12
Speaker 3: piece of work.
32:13
Speaker 2: I agree, But I mean in the way that human
32:16
Speaker 2: stories always go. You know, people were talking to each other,
32:20
Speaker 2: and Wilson had been at Bryn Marr right before she
32:23
Speaker 2: got there, and her PhD advisor kept collaborating with Wilson,
32:27
Speaker 2: and so like, this is a question they all wanted
32:29
Speaker 2: to have answered, So they were all kind of working
32:31
Speaker 2: on it concurrently, and so there was a lot of
32:33
Speaker 2: discussion between them. Nettie made this really nice, really clear observation.
32:37
Speaker 2: Wilson also made some great clear observations. So I mean,
32:40
Speaker 2: to me, it would be great if Nettie Stevens and
32:44
Speaker 2: Wilson were both known for the discovery of sex chromosomes.
32:47
Speaker 2: But you know who got the credit.
32:48
Speaker 3: I'm guessing it's not Natie Stevens because I'd never heard
32:51
Speaker 3: of her and neither had the listeners. So then is
32:53
Speaker 3: it Wilson?
32:54
Speaker 1: No, it's Thomas Hunt Morgan. And after the break we'll.
33:00
Speaker 8: Talk about why.
33:19
Speaker 3: All right, we are back from the break, and Kelly
33:21
Speaker 3: just dropped a big bomb on us bringing in a
33:24
Speaker 3: dark horse. Kelly, you can't just bring in a new
33:26
Speaker 3: character and act three without laying the pipe in act one.
33:29
Speaker 3: I mean, don't you have you taken screenwriting? One oh one?
33:32
Speaker 3: Who is this Thomas Hunt Morgan fellow? And why does
33:35
Speaker 3: he get the credit for Wilson and Stevens independent work.
33:38
Speaker 2: Well, I'm going to try to not have my feelings
33:40
Speaker 2: hurt too much because I had mentioned Thomas Hunt Morgan earlier.
33:44
Speaker 5: Oh no, a couple of.
33:46
Speaker 2: Times, but you know, we were throwing a lot of
33:47
Speaker 2: names around, so maybe it didn't stick.
33:49
Speaker 1: But he was her PhD advisor.
33:51
Speaker 3: So Morgan is Steven's PhD advisor?
33:54
Speaker 5: Yes, oh nice.
33:56
Speaker 3: No, I totally take it back. You absolutely did lay
33:58
Speaker 3: the groundwork, but like an excellent novel, I overlooked the
34:01
Speaker 3: important clues.
34:02
Speaker 2: Oh man, maybe I'm the next Agatha Christian exactly.
34:07
Speaker 3: So is just the standard case of PhD advisor gets
34:10
Speaker 3: credits for grad student work? Is their gender stuff at
34:12
Speaker 3: play here?
34:13
Speaker 2: There's definitely sexism at play here. First of all, it's
34:16
Speaker 2: kind of ironic because Morgan, at the time that Wilson
34:19
Speaker 2: and Stevens published their result, he was like, not super
34:22
Speaker 2: sure about this sex chromosome thing. He was like, well,
34:25
Speaker 2: maybe that's not how it works.
34:27
Speaker 1: He still needed to.
34:27
Speaker 2: Be convinced at the time these results came out. But
34:31
Speaker 2: in nineteen oh six there was a conference and both
34:34
Speaker 2: Morgan and Wilson were invited to give talks about their
34:38
Speaker 2: theories of how sex is determined. So how you end
34:41
Speaker 2: up with individuals that make sperman and how you might
34:42
Speaker 2: end up with individuals that make eggs. But Stevens was
34:46
Speaker 2: not invited.
34:47
Speaker 3: And is Wilson already like a professor and Stevens is
34:49
Speaker 3: a grad student? Is that how it works?
34:51
Speaker 2: Wilson is already a professor, Stevens has finished her PhD,
34:55
Speaker 2: but she's in a part of her career where she's
34:57
Speaker 2: having trouble getting the professorship that she deserves. Right, So
35:01
Speaker 2: actually it will take five maybe seven years for her
35:05
Speaker 2: to finally get offered a professorship. So she gets offered
35:09
Speaker 2: a post doc at Carnegie Institute, Washington, and then she
35:12
Speaker 2: gets to go back to Brent Mahr as a research associate,
35:15
Speaker 2: but she doesn't get a faculty position. A couple years later,
35:19
Speaker 2: they offer her that faculty position, but before she can
35:22
Speaker 2: accept it, she dies of breast cancer.
35:24
Speaker 3: Oh gosh, all right, So before we dig into that, Tragy,
35:29
Speaker 3: let's go back to the conference you were talking about
35:30
Speaker 3: where her advisor Morgan and her sometimes friendly rival Wilson
35:34
Speaker 3: both get offered big talks to give their theories of
35:38
Speaker 3: sex determination. But she doesn't, and she's also the most
35:42
Speaker 3: junior person of the.
35:43
Speaker 2: Three, right right, and dying early is actually part of
35:46
Speaker 2: the story here.
35:46
Speaker 3: Oh wow.
35:47
Speaker 2: Wilson and Morgan both go on to become even more
35:50
Speaker 2: well known scientists. Morgan in particular ends up doing amazing
35:54
Speaker 2: work on fruitflies, attributing particular genes to particular traits in
35:59
Speaker 2: these fruitflies. And when Stevens dies, Morgan writes her obituary.
36:06
Speaker 3: Oh wow, he.
36:06
Speaker 2: Writes her obituary in science and he doesn't get all
36:10
Speaker 2: of it right.
36:11
Speaker 3: Oh gosh, this is like a Morgan character assassination here.
36:16
Speaker 3: I feel like we need to have somebody from the
36:17
Speaker 3: Morgan estate onto. But some of this like equal time.
36:21
Speaker 1: I mean, okay, so let's take a step back here.
36:22
Speaker 2: He was the advisor for Women Scientist, which was very
36:25
Speaker 2: progressive at the time. I think maybe he wasn't being
36:29
Speaker 2: aggressive here, but let's dig in a little bit. So
36:32
Speaker 2: in the obituary he says that Steven's confirmed McClung's hypothesis.
36:38
Speaker 2: And you might remember that McClung was the guy who
36:40
Speaker 2: was like, X makes males and he got it exactly wrong.
36:44
Speaker 2: So she didn't confirm his hypothesis.
36:47
Speaker 3: She flipped it on its head.
36:49
Speaker 2: She flipped it on his head and then did a
36:51
Speaker 2: bunch of extra work to make a much more sound argument.
36:53
Speaker 2: And so here her contributions are getting sort of obscured.
36:56
Speaker 2: So she's already getting cut out of the conversation. Her
37:00
Speaker 2: contributions are not being attributed correctly in her obituary.
37:04
Speaker 3: But Morgan must have known, right, I mean, obviously, he's
37:06
Speaker 3: like a big man in his field. He was her advisor.
37:09
Speaker 3: He's right there, he understands all this stuff. He must
37:11
Speaker 3: have known what he was doing. Is is there anybody to
37:13
Speaker 3: see this other than being an intentional obscuring of her
37:16
Speaker 3: name and deflating of her credit.
37:18
Speaker 1: I think that's probably what happened.
37:19
Speaker 2: Maybe we should get somebody who's like a Morgan expert
37:22
Speaker 2: on and maybe they can say, like, oh, this was
37:24
Speaker 2: during a period where he was drinking too much and
37:27
Speaker 2: he was just sloppy and something like that. I don't know,
37:30
Speaker 2: Maybe there's a nicer way to look at it. But
37:33
Speaker 2: I had a PhD student and they died and I
37:35
Speaker 2: was writing their obituary, and especially if they were like
37:37
Speaker 2: one of the first women in their field, I feel
37:40
Speaker 2: like I would be very careful about how I wrote
37:42
Speaker 2: that obituary. But so he either was sloppy or he was,
37:47
Speaker 2: you know, being dishonest.
37:49
Speaker 3: But there is a long history of PhD advisors taking
37:52
Speaker 3: credit for graduate student work, and especially when it's a
37:55
Speaker 3: male advisor and a female student. And they have lots
37:59
Speaker 3: of examples of like a man winning the Nobel Prize
38:02
Speaker 3: for work done by their female graduate student. So it's
38:04
Speaker 3: definitely not just biology, and at the time I think
38:07
Speaker 3: it was very common, unfortunately, right.
38:09
Speaker 2: And here's another piece of evidence that sort of builds on,
38:12
Speaker 2: you know, the argument that you just made. Morgan eventually
38:14
Speaker 2: writes a textbook called The Mechanisms of Genetics, and he
38:18
Speaker 2: talks about the work that Stevens and Wilson did, but
38:22
Speaker 2: he doesn't mention I don't think he mentions either of
38:25
Speaker 2: their names, but he definitely doesn't mention her name, oh Man.
38:28
Speaker 2: And the way that he wrote it was right before
38:30
Speaker 2: he talked about the contributions that he made to the field,
38:34
Speaker 2: and when you read it, you could be forgiven for
38:36
Speaker 2: thinking that he was on that you know, whole section
38:39
Speaker 2: just describing his contribution.
38:41
Speaker 5: Oh Man.
38:42
Speaker 3: Not a fan of Morgan over here, I'm.
38:44
Speaker 2: Feeling a little grumpy about Morgan too, and in nineteen
38:48
Speaker 2: thirty three he goes on to get a Nobel Prize,
38:50
Speaker 2: not for the discovery of sex determination, but just for
38:53
Speaker 2: his general work in genetics, and so over time she's
38:57
Speaker 2: just sort of been forgotten. And so a lot of
38:59
Speaker 2: people forget about both Wilson and Stevens because Morgan became
39:04
Speaker 2: such a hot shot, and a lot of people read
39:06
Speaker 2: this textbook, and I think a lot of them just inferred, oh, okay,
39:09
Speaker 2: Morgan was the one who figured that out too, And
39:11
Speaker 2: so over time, Stevens has been forgotten, and so has
39:15
Speaker 2: Wilson relative to Morgan, and Morgan has gotten a bunch
39:17
Speaker 2: of the credit.
39:18
Speaker 3: I think a lot of people don't appreciate how much
39:20
Speaker 3: campaigning and politicking there is in getting a Nobel Prize.
39:24
Speaker 3: Like it's not just you do a bunch of good
39:25
Speaker 3: science and then you're recognized. It's not some like pure meritocracy.
39:29
Speaker 3: You know, there's a lot of behind the scenes campaigning
39:32
Speaker 3: like this person should get the credit, and this person
39:34
Speaker 3: should get the credit, and this is really important. Like
39:36
Speaker 3: the folks who get the Nobel Prize are the ones
39:38
Speaker 3: who bubble up to the top of that campaign and
39:41
Speaker 3: every year. There's lots of arguments and discussion, and so
39:45
Speaker 3: wrangling your way into the textbooks and getting the story
39:48
Speaker 3: told a certain way is definitely a good way to
39:50
Speaker 3: lay the groundwork for later getting the Nobel Prize. So
39:53
Speaker 3: I don't know that that's what Morgan was doing, and
39:55
Speaker 3: Nobel prizes were definitely a newer thing back then, but
39:59
Speaker 3: you know, writing your into the history of science is
40:01
Speaker 3: not a new game.
40:03
Speaker 2: Yeah, unfortunately, and I think often women aren't playing the game,
40:08
Speaker 2: or aren't in a position where they can play the
40:09
Speaker 2: game the same way.
40:11
Speaker 3: I saw this happening like in person. When we discovered
40:13
Speaker 3: that the Higgs boson, we knew that somebody was going
40:16
Speaker 3: to get the Novel Prize for it, and all of
40:17
Speaker 3: a sudden, there were lots of theorists giving talks about
40:20
Speaker 3: their contribution to Higgs theory and the role they played
40:23
Speaker 3: in bringing it to the discovery because everybody knew it
40:27
Speaker 3: could be shared between three people, and Higgs was getting it,
40:29
Speaker 3: but who else was going to get it? So there's
40:31
Speaker 3: a lot of campaigning, a lot of talks on that topic,
40:34
Speaker 3: the history of those discoveries, and it was very clear
40:36
Speaker 3: what was happening.
40:37
Speaker 2: I think one day we should talk about your research
40:39
Speaker 2: in particular. But were you one of those people who
40:41
Speaker 2: could have campaigned? Were you around during the HAGS time?
40:46
Speaker 3: I mean I was on one of the teams. But
40:47
Speaker 3: one question in the air was were they going to
40:50
Speaker 3: give it to theorists who came up with the idea
40:52
Speaker 3: or to experimentalists who discovered it or both. In the end,
40:56
Speaker 3: they gave it just to theorists, which is still sort
40:59
Speaker 3: of controversial. And if they had given it to experimentalists,
41:02
Speaker 3: probably they would have only given it to the heads
41:05
Speaker 3: of the experiments because the experiments have five thousand people
41:08
Speaker 3: on it and you can't give them all the Nobel Prize.
41:11
Speaker 3: That might be one reason why they only gave it
41:13
Speaker 3: to a theorist, because how do you decide which experimentalist
41:16
Speaker 3: do give it to? Sort of a frock question. But yeah,
41:20
Speaker 3: I contributed, I was on those papers. I was there.
41:23
Speaker 1: Oh that's exciting.
41:23
Speaker 3: Though I don't think I deserve a Nobel Prize for
41:25
Speaker 3: my contribution. I'm not going to be campaigning for that.
41:28
Speaker 3: But it was fascinating to see the human side of it,
41:31
Speaker 3: to see people actively out there arguing that they deserve
41:35
Speaker 3: the Nobel Prize. And I know that that was influential.
41:38
Speaker 2: Okay, yeah, that is an interesting insight I don't think
41:40
Speaker 2: I had on my radar. Yeah, okay, that's sort of
41:43
Speaker 2: like the history there. But one of the things that
41:44
Speaker 2: I wanted to talk about briefly is how different this
41:48
Speaker 2: story could have been if it wasn't the case that
41:52
Speaker 2: why chromosomes are a different shape, and so maybe it
41:57
Speaker 2: would have ended up with the same thing, because there
41:58
Speaker 2: were some males who justs weren't getting anything, you know,
42:01
Speaker 2: they weren't getting like a paired chromosome at all, and
42:03
Speaker 2: that's how they became the males.
42:05
Speaker 1: But why chromosomes.
42:06
Speaker 2: It turns out, over time they tend to degrade, and
42:10
Speaker 2: so the idea is that most chromosomes often swap material
42:14
Speaker 2: at the beginning of myosis. And this process of swapping
42:18
Speaker 2: allows you to get rid of genes that have kind
42:20
Speaker 2: of gotten messed up or they've gotten some bad mutations.
42:24
Speaker 2: But if you have this part of a chromosome that's
42:26
Speaker 2: now controlling you know, for example, say it has the
42:29
Speaker 2: code for making testes and for a beard and for
42:34
Speaker 2: a vast deference, you don't want to be swapping that
42:37
Speaker 2: and risk getting those male related genes onto the female
42:42
Speaker 2: related chromosome, so they stop doing that recombination. But that
42:46
Speaker 2: means that anything else that's also on that chromosome that
42:49
Speaker 2: doesn't have anything to do with maleness has now not
42:51
Speaker 2: getting sort of like rejuvenated or removed by this crossing
42:55
Speaker 2: over process. And so over time those genes, as they
42:58
Speaker 2: get messed up, we think they sort of like they
43:01
Speaker 2: fall off because you're not using them anymore. And every
43:03
Speaker 2: once in a while chromosomes sort of lose bits, and
43:06
Speaker 2: sometimes that's a problem, sometimes it's not. But over time,
43:09
Speaker 2: the Y chromosome tends to degenerate, and you also see
43:12
Speaker 2: this in birds. It's a different chromosome. The males have
43:15
Speaker 2: Z and Z and the females have Z and W,
43:19
Speaker 2: and that W chromosome is the one that has started
43:22
Speaker 2: to degenerate, so it's also started to lose things. So
43:25
Speaker 2: this observation, like, it seems to me that the reason
43:29
Speaker 2: we started with sex was because of this weird way
43:32
Speaker 2: that these chromosomes sort of change shape over time. And
43:34
Speaker 2: if you hadn't had that clue that these things are
43:36
Speaker 2: different shapes, it would have been much harder to make
43:38
Speaker 2: this observation. And I don't know that just seemed interesting
43:41
Speaker 2: to me while I was going through this research.
43:43
Speaker 3: Yeah, because it's sort of macroscopic. I mean, you're zooming in,
43:45
Speaker 3: you're using the microscope, but you don't need to look
43:48
Speaker 3: at the actual genome and decode it and like see
43:50
Speaker 3: the structure of DNA to see that there's something different
43:53
Speaker 3: between the X and the Y, even just under a microscope.
43:56
Speaker 2: And the other thing that's kind of amazing is that
43:58
Speaker 2: they were able to figure out anything out because the
44:02
Speaker 2: way that whether or not you get an individual that
44:04
Speaker 2: produces sperm or eggs or produces both, if they're hermaphrodites,
44:07
Speaker 2: like the various mechanisms through which those things come about
44:11
Speaker 2: are super varied. Like reptiles, it does depend on temperature.
44:15
Speaker 2: And then in the birds, they've got like the opposite,
44:17
Speaker 2: like we just talked about. The females are the ones
44:19
Speaker 2: that have the different kinds of chromosomes. And you get
44:22
Speaker 2: some animals that are sequential hermaphrodites. They've got all the
44:26
Speaker 2: genetic code that you need to make either decision, and
44:28
Speaker 2: they can switch between what sets of code they're using.
44:31
Speaker 2: And while I was reading about sex determination stuff, there
44:34
Speaker 2: were papers that had titles like sex, chromosome evolution. So
44:39
Speaker 2: many exceptions to the rules. It's like, there are just
44:43
Speaker 2: so many different ways that this all works out. It's
44:45
Speaker 2: kind of amazing we were able to get a foothold,
44:46
Speaker 2: but we did.
44:48
Speaker 3: Yeah, that's incredible. Everything is messy. It's incredible. You can
44:51
Speaker 3: tell any story. What do we know about the history
44:53
Speaker 3: of this? You're talking about how over time these degrades.
44:57
Speaker 3: What is the history and the evolution of sex in biology? Like,
45:01
Speaker 3: do we know when things went from asexual to having
45:05
Speaker 3: two genders?
45:06
Speaker 2: So I think that there were a number of different transitions.
45:10
Speaker 2: And I am absolutely not an expert in this. This
45:12
Speaker 2: would be a whole topic on its own, I think,
45:14
Speaker 2: But from my reading, what I think I was picking
45:17
Speaker 2: up was that often when you end up with a transition,
45:20
Speaker 2: and you end up with offspring that either just have
45:22
Speaker 2: eggs or just make sperm, that usually starts from a
45:26
Speaker 2: hermaphroditic ancestor, so you have the code to do both,
45:30
Speaker 2: and then in some individuals, the set of codes for
45:33
Speaker 2: male traits is turned off, and for some individuals the
45:35
Speaker 2: set of codes for female traits gets turned off, and
45:38
Speaker 2: you end up producing individuals that can no longer produce
45:41
Speaker 2: both sperm and eggs. They produce only sperm or eggs,
45:45
Speaker 2: and why that would be beneficial to lose that ability
45:49
Speaker 2: to do both is maybe a little bit unclear. I
45:51
Speaker 2: think one of the leading hypotheses is that there's often
45:55
Speaker 2: not a benefit to reproducing with yourself, So hermaphrodites can
45:59
Speaker 2: often mix their own sperm and eggs to produce offspring.
46:03
Speaker 2: But in an evolutionary sense, the extra genetic diversity that
46:06
Speaker 2: you get by mating with individuals other than yourself has
46:10
Speaker 2: a huge payoff in terms of being able to like
46:12
Speaker 2: stay ahead of parasitic infections and stuff. Yeah, and so
46:15
Speaker 2: I think there's selective pressure for forcing an individual to
46:19
Speaker 2: mate with other individuals, whereas if you're aromaphroditic, maybe you're like, oh,
46:22
Speaker 2: it's easier to just mate with me.
46:26
Speaker 1: We've all been there.
46:27
Speaker 3: I'm going to stay in. It's Friday night and I'm tired.
46:30
Speaker 1: That's right, that's right. And that's where the show gots
46:33
Speaker 1: not appropriate for kids.
46:34
Speaker 7: Maybe.
46:35
Speaker 3: Well, I think about that because we talk about earliest
46:38
Speaker 3: common ancestor and how all life on Earth probably has
46:41
Speaker 3: a single ancestor, but you know, we have gender along
46:44
Speaker 3: the line at some point, and we didn't have it
46:46
Speaker 3: early on, which means that at some point it must
46:48
Speaker 3: have you know, sprung up. And so it's fascinating to
46:51
Speaker 3: me to think about the history of this and where
46:53
Speaker 3: it diverges. And maybe one day we'll have the whole
46:56
Speaker 3: tree of life all the way back through time and
46:58
Speaker 3: we'll know the answers to all these questions.
47:00
Speaker 2: Bacteria started with like conjugation, where they'd just be like
47:02
Speaker 2: passing over small chunks of genes, and so there's been
47:05
Speaker 2: a lot of diversity along the way. And without going
47:08
Speaker 2: into too long of a diatribe about definitions, because to
47:12
Speaker 2: be honest, I'd like to check my definitions before saying
47:14
Speaker 2: them publicly. You know, gender, I think is often now
47:16
Speaker 2: thought of as being different than just do you make
47:19
Speaker 2: sperm or do you make eggs. It's more about the
47:23
Speaker 2: strategy that you employ as you go through life, and
47:25
Speaker 2: so that's a slightly different thing. Just to get our
47:27
Speaker 2: terms correct. And so today we were specifically talking about
47:30
Speaker 2: gomedic sex. So do you end up with the genetic
47:33
Speaker 2: code to make sperm or do you end up with
47:34
Speaker 2: the genetic code to make eggs?
47:36
Speaker 3: All right, so finish the story of Nettie Stevens for
47:39
Speaker 3: us tell us about how she tragically passes away.
47:42
Speaker 2: Yeah, so she finally gets offered that professorship at Bryn Mar,
47:45
Speaker 2: which she quite clearly earned because two years before she
47:48
Speaker 2: got this offer. You know, as we mentioned, she was
47:50
Speaker 2: listed in the one thousand Top Men of Science, so
47:54
Speaker 2: she was again one of eighteen women. So she was
47:56
Speaker 2: clearly globally known for the work that she was doing,
47:59
Speaker 2: and she had one ward for her work on sex chromosomes.
48:02
Speaker 2: So I think everybody realized that she was making big contributions.
48:06
Speaker 2: But by the time she was ready to start that professorship,
48:09
Speaker 2: she died at age fifty of breast cancer. And so
48:12
Speaker 2: who know, I mean, she still had like a prolific
48:14
Speaker 2: publication record up until that point. I think she had
48:17
Speaker 2: published something like forty papers and that was.
48:20
Speaker 1: Like, you know what.
48:20
Speaker 2: She got her PhD in nineteen oh three. Wow, And
48:23
Speaker 2: so in maybe a fifteen year period if you include
48:25
Speaker 2: when she was working on her master she managed to
48:27
Speaker 2: really knock out a bunch of papers, which to me
48:30
Speaker 2: is incredible, especially when you consider the tide that she
48:33
Speaker 2: was working against at the time.
48:35
Speaker 3: This is like a Mary Currie type story. Could the
48:37
Speaker 3: work she was doing somehow have contributed to her breast cancer,
48:40
Speaker 3: where she using like really dangeruis chemicals and this kind
48:44
Speaker 3: of stuff in the lab to do her studies. Or
48:46
Speaker 3: is this just random and bad luck.
48:48
Speaker 1: Oh that's interesting.
48:49
Speaker 2: I didn't come across anyone who was suggesting that the
48:52
Speaker 2: work is what ended up killing her. She was using
48:54
Speaker 2: a lot of different kinds of stains, and so stains
48:57
Speaker 2: make it easier to see the chromosomes as they and
49:00
Speaker 2: as they separate. I don't know if any of those
49:02
Speaker 2: stains were also chriscinogenic, so we're also likely to cause cancer.
49:07
Speaker 2: It's possible, but I don't know.
49:09
Speaker 3: As long as we're just listing possibilities. You know, maybe
49:11
Speaker 3: Morgan somehow poisoned her. Yes, let's further smirch his character anyway,
49:18
Speaker 3: that's right.
49:20
Speaker 2: I wonder if we're going to get angry emails, But
49:22
Speaker 2: you know, we'll invite them on the show and they
49:24
Speaker 2: can defend Morgan if they'd like.
49:25
Speaker 3: That would be interesting, exactly if you are Thomas Morgan
49:28
Speaker 3: the fourth or whatever, and you are grippy at hearing
49:30
Speaker 3: your great great grandfather's characters merged right in and we
49:33
Speaker 3: will clear the air.
49:34
Speaker 2: But smirched is a great word that's not used nearly
49:37
Speaker 2: as often as it should be.
49:39
Speaker 3: It feels sort of very nineteen hundreds.
49:40
Speaker 1: I thought it was er appropriate, absolutely error appropriate.
49:44
Speaker 2: So anyway, reading about Nettie made me like totally appreciate
49:49
Speaker 2: I have had difficult sort of steps in my journey.
49:52
Speaker 2: I did end up leaving like a master's lab because
49:54
Speaker 2: of sexual harassment and so like it. You know, hasn't
49:57
Speaker 2: been one hundred percent easy, but tip to what she.
50:00
Speaker 1: Had to go through, then I've had an easy path.
50:04
Speaker 2: Anyway, It's just kind of a bummer to hear about
50:05
Speaker 2: a woman who was doing amazing work, and you know,
50:08
Speaker 2: I think it would be reasonable to say that she
50:10
Speaker 2: and Wilson should both jointly be known for this incredible discovery.
50:13
Speaker 1: But you know, we.
50:14
Speaker 2: All think of it as Morgan's which is just a
50:17
Speaker 2: bummer on a lot of levels.
50:18
Speaker 1: So there you go.
50:19
Speaker 3: Here we are pushing gently back against Morgan's politicking to
50:23
Speaker 3: get himself in the top men of science.
50:25
Speaker 2: There we go, Well, he got a noble price, so
50:27
Speaker 2: I think he won, and we're a little too late,
50:29
Speaker 2: but hopefully y'all will remember the name Nettie Stevens and
50:33
Speaker 2: We'll go ahead and share this story with other people
50:35
Speaker 2: and Nettie will get.
50:36
Speaker 1: The credit she deserves.
50:37
Speaker 3: Congrats and Nittie on all of your discoveries.
50:40
Speaker 1: Way to Go, NTTI.
50:48
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