Of lice and men

Daniel and Kelly explore what lice can teach us about human evolution, and the role lice have played in some of humanity's most devastating wars. 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?

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• 1:32Kelly Weinersmith?

  Howdy, extraordinaries. Today, we're discussing human lice. If you're a parent, you may be at the stage in your life where you're worried about kids bringing home lice from school. But back in your wilder days, if you had wilder days, there may have been another kind of lice found on a different part of the body that you worried about. Maybe it made you feel, let's say, crabby? We're talking about both kinds of lice today and some historically catastrophic diseases that lice frequently caused in the past. So decide if this episode is appropriate for you or young ears that might also be listening. Thanks.

• 2:23Kelly Weinersmith?

  When you grab a lice comb and spend hours picking through your kid's hair to remove those little buggers, you're engaging in a time honored human tradition that stretches for millennia. Direct evidence of human head lice goes back 10,000 years, and we've found 6,500 year old head lice combs in Egypt. But we've probably had head lice even earlier than that, perhaps even since the dawn of our species. So if this pest has been with us during our entire journey as a species, then can studying it tell us anything about our past? Or can studying it at least tell us how to get rid of it better? Welcome to Daniel and Kelly's Lousy Universe.

• 3:21Daniel Whiteson?

  Hi, I'm Daniel. I'm a particle physicist who likes to think about aliens and my family's had lice more times than I can count.

• 3:29Kelly Weinersmith?

  Hello, I'm Kelly Wiener Smith. I study parasites and space and my family has never had lice, but we have had fleas.

• 3:38Daniel Whiteson?

  Not even once in a lice time?

• 3:41Kelly Weinersmith?

  Ah, what a lousy joke.

• 3:46Daniel Whiteson?

  It's not even my joke. It's literally the name of the place we took our kids to get them de-loused.

• 3:51Kelly Weinersmith?

  Oh, man. I don't know how we avoided it because my daughter like puts on other people's hats and like, well, you know, she'll be like, oh, yeah. I was like, your hair looks brushed. How did that happen? And she's like, I borrowed a friend's brush at school. And I'm like, oh, somehow we have managed to completely avoid lice. I don't know how. It blows my mind.

• 4:10Daniel Whiteson?

  Maybe something about your remote living on your enclave escaping humanity, you know?

• 4:14Kelly Weinersmith?

  Yeah, but I don't know. She still goes to school where they like, I don't know. It's where they greet each other by like licking each other's hands and then rubbing their heads together. Like, kids are weird and gross.

• 4:26Daniel Whiteson?

  Well, I was gonna ask you about whether your family had lice, but now I want to hear all about how you got fleas. Which animal on the farm passed them to you?

• 4:35Kelly Weinersmith?

  No, this was before, this was when we lived in a city. This blew my mind. Okay, so we, we lived in Houston and we had two cats and we had just had our second baby, that our second baby just came home. So we were like out of our minds with like exhaustion and like, you know, the delirium that comes along with having a new baby at home. And it was winter and so I forgot to give our cats their flea medication, but they're 100% indoor cats. And it was winter. So I was like,

• 5:03Daniel Whiteson?

  Winter in Houston.

• 5:03Kelly Weinersmith?

  Winter in Houston. Yeah, winter in Houston. So.

• 5:06Daniel Whiteson?

  What's the relevance of winter? I'm not following.

• 5:08Kelly Weinersmith?

  I think there's fewer fleas outside in the winter. I don't know. It's cold. I don't, I probably.

• 5:14Daniel Whiteson?

  Fleas all migrate to Mexico in the winter or something?

• 5:17Kelly Weinersmith?

  Yes. No, no, I guess I don't know much about fleas, but somehow in my head, it's less likely that someone's gonna like walk around in the grass and bring a flea that could infect a cat back into your house or something. And then they're gonna find your cats. Anyway, somehow my 100% indoor cats got fleas. And I didn't realize it until I was changing a diaper and I saw something hop.

• 5:42Daniel Whiteson?

  Wow.

• 5:43Kelly Weinersmith?

  And there was a flea on my kid and I was like, I am the worst mother in the whole world. And so immediately I.

• 5:51Daniel Whiteson?

  You're not, but that doesn't nominate you for being the best mother in the world.

• 5:55Kelly Weinersmith?

  That was an emotional roller coaster there. I felt a little better and then I felt real bad again. And so.

• 6:00Daniel Whiteson?

  It's hard to compliment somebody for having fleas on their baby.

• 6:03Kelly Weinersmith?

  You didn't have to like rank me at all. I could just tell the story. And anyway, well, your family has had lice an uncountable number of times. So I don't think either one of us are winning parents of the year.

• 6:16Daniel Whiteson?

  I'm not suggesting it's like 17,000. I'm just saying it's often enough that I didn't even keep track. It's like two or three times. I'm not even sure. It just felt like a routine. I remember going back to once in a lifetime and being like, I thought we were supposed to only be here once in a lifetime. Isn't that the idea?

• 6:34Kelly Weinersmith?

  Oh, well, that's false advertising because you can get lice over and over and over again.

• 6:38Daniel Whiteson?

  That's true. But I do love how this whole field is riddled with terrible puns.

• 6:42Kelly Weinersmith?

  Yeah, yeah. Well, I may think from lice come many words like nitpicking. Yeah, I mean, we've had, like, the Bible has stories about lice as a plague. Like, this has been part of our history for a really long time. You know, like, we find evidence of lice on mummies, which is amazing because lice shouldn't preserve well, right? So the fact that you find any of them probably means there were loads of them.

• 7:08Daniel Whiteson?

  Are they also individually wrapped in little mummy cloths?

• 7:11Kelly Weinersmith?

  Ah, no, no, because nobody was trying to bring them with them into the afterlife. But, but there's an old document called the Papyrus Eburors. That's like, you know, an ancient Egyptian document that has a recipe for how to make like, a thing to kill lice. And so we've, we've been dealing with this for a long time, probably from like, literally the beginning of our species, which we're going to get to.

• 7:32Daniel Whiteson?

  Interesting. Well, I've had my own personal evolution with my feelings about lice because I used to feel like, oh, my God, that is the creepiest thing. You have these little animals that are crawling all over you. They're like mating and pooping and doing all this stuff. Yuck. But, you know, then I met Katrina and I got married to her. And now I fully understand that every surface of my body is a little ecosystem. And I'm always going to be covered in little critters, little microbes doing this, that, and the other. And lice are just, you know, they're like the elephants in that forest and like, whatever, man.

• 8:05Kelly Weinersmith?

  I totally disagree with you, but I don't want, I don't want to dissuade you from this story. You've told yourself to make yourself feel better. So I think we should move on to the question that prompted this episode.

• 8:20Daniel Whiteson?

  Let's not dig into Daniel's psychological issues. Let's answer questions from listeners. So Kelly, why are we talking about lice today?

• 8:27Kelly Weinersmith?

  Well, we have this amazing Discord community and you can join us by going to danielandkelly.org and clicking on the link to join our Discord community. And in Discord, user Bauer Family told this story that they sort of vaguely remembered about how the divergence time between pubic lice and head lice can tell you about when we became hairless. Because when we lost the hair on, you know, like our bellies and our shoulders or whatever, there now was like a big gulf between, you know, any lice that are in your hair and any lice that are in your pubic region. And actually, the hair in your pubic region is quite different in like texture and thickness and stuff than the hair on your head.

• 9:12Kelly Weinersmith?

  And so the idea here is if you could date the divergence between those two lice species, you can figure out when humans became mostly hairless.

• 9:22Daniel Whiteson?

  This is like having a population of animals on some continent and then it splits it into two and you can track them individually.

• 9:28Kelly Weinersmith?

  Exactly, yes. Allopathic speciation is when you get like a physical barrier between what was once one population, now it becomes two. And over time, they separate enough that they become different species and, you know, maybe can't even breed together anymore.

• 9:41Daniel Whiteson?

  Wow.

• 9:42Kelly Weinersmith?

  So this was like a story that they had heard and they wanted to know more. It's totally wrong, which we're gonna get to.

• 9:49Daniel Whiteson?

  Totally wrong.

• 9:50Kelly Weinersmith?

  Totally wrong.

• 9:51Daniel Whiteson?

  It sounds like such a cool science story.

• 9:53Kelly Weinersmith?

  It does.

• 9:53Daniel Whiteson?

  And I was gonna make all these jokes about pubic island.

• 9:56Kelly Weinersmith?

  Well, you still can, because we're gonna still talk about pubic lice and they're interesting. But yet, like in general, as I was going through and doing the research, I realized there were all of these things I had heard about lice that when you dig into the research are totally not substantiated by the science. And so we are going to be dispelling lousy stories today on DKU.

• 10:16Daniel Whiteson?

  Well, is this gonna be a wet blanket episode? Or are we gonna come away with an even more interesting, actually substantiated science story?

• 10:23Kelly Weinersmith?

  Yeah, those things are not mutually exclusive, so we're gonna do both.

• 10:28Daniel Whiteson?

  So let's dig into it. Start us off with an introduction to lice because I think I have this idea that lice are these basically tiny little crawling critters, maybe like a shrunken down version of a beetle that's living on me.

• 10:41Kelly Weinersmith?

  Yeah, so they don't have wings. They can only like crawl. So fleas can jump, but lice can only crawl. They're very slow moving. So pretty much the only way they get from one host to another is like physical contact. And so you need to like, maybe one gets stuck in a hat and then you put that hat on your head and now it is on you. But they're not jumping from host to host.

• 11:01Daniel Whiteson?

  And so how big are these things?

• 11:03Kelly Weinersmith?

  They're about the size of like a sesame seed or a pencil tip. So they're, they're tiny.

• 11:08Daniel Whiteson?

  Oh, oh, that's actually bigger than I thought. I thought they were going to be almost impossible to see.

• 11:12Kelly Weinersmith?

  No, no, no. I mean, I guess you offloaded the job of nitpicking your kids to Once Upon a Lace. What was it? Once in a Lace Time? Lots of free advertising for Once in a Lace Time today. But, but if you take like, you know, a lace comb and you go through, you can see, especially if you have dark hair, you can see the eggs, which are even smaller. And then you can see the adults and you can, you know, get them out with a lace comb.

• 11:38Daniel Whiteson?

  I see. And are these guys insects or are they arthropods or something else? Like, if you made this thing like the size of a football, what would it look like?

• 11:47Kelly Weinersmith?

  Okay, so that they are arthropods and they're insects. And if you zoomed in, so their bodies, you know, there's like, I think something like 5,000 species of like what you would maybe count as lice. But like for human lice, you know, their bodies are, some of them kind of look football shaped, the like base part of their body, although pubic lice tend to be a little bit more like flattened. But anyway, and then they've got six appendages that stick out and they've got sort of like hooky hands that they use to like cling to your hair, to like hug your hair or hold on to it, sort of like the way a sloth holds on to like a tree branch. And then they've got like heads with antenna and they look

• 12:28Kelly Weinersmith?

  pretty clear-ish or like orangey-ish most of the time, unless they've got some, a blood meal, then they can be kind of red.

• 12:35Daniel Whiteson?

  So do they look like tiny ticks, basically?

• 12:39Kelly Weinersmith?

  Ticks, how would I say they're different? So the tick body tends to be like more smooth, whereas a lice body looks a little bit more like ridged to me.

• 12:48Daniel Whiteson?

  All right. But they're tiny little creepy crawlies.

• 12:51Kelly Weinersmith?

  Yeah.

• 12:51Daniel Whiteson?

  And you said something fascinating. You said there's thousands of species of lice. But not all of them are human lice. How many species are there of human lice?

• 13:00Kelly Weinersmith?

  So there's two species of lice that you commonly find on humans. And that's the head slash body louse. And we're going to spend a lot of time talking about that slash a little bit later. It's a, it's a very important slash.

• 13:15Daniel Whiteson?

  Okay, but the different species of lice are connected to the different species of hosts. Right? So like

• 13:20Kelly Weinersmith?

  Yes.

• 13:20Daniel Whiteson?

  chimp lice is different from human lice is different from dog lice. So I'm not going to get lice from my dog and you weren't going to get lice from your cat.

• 13:28Kelly Weinersmith?

  That's right. Well, so what

• 13:29Daniel Whiteson?

  Okay.

• 13:29Kelly Weinersmith?

  That the cat story, those were fleas.

• 13:31Daniel Whiteson?

  Right.

• 13:32Kelly Weinersmith?

  Very different, actually. I know they don't sound different, but like the fact that they can hop, I mean, their legs are like totally different.

• 13:38Daniel Whiteson?

  I know, I remember that fleas and lice are different, but I was making the point that like if your cat had fleas and lice, you could get its fleas, but not its lice.

• 13:45Kelly Weinersmith?

  Yeah, yeah, we got their fleas, but if they had had lice, we wouldn't have gotten their lice.

• 13:48Daniel Whiteson?

  All right.

• 13:48Kelly Weinersmith?

  Yeah, yeah. Yeah, so lice tend to be very, very host specific. And you tend to find lice in two different flavors. It's a gross way of saying it. There are scavenger lice, which eat like dead skin pieces and stuff. We don't have those kinds of lice on human bodies. Unfortunately, because what we have are the sucking lice, which have like a thing that they shove into your body so that they can suck blood. And yeah, they're like feeding on blood.

• 14:17Daniel Whiteson?

  So they're like crawling mosquitoes?

• 14:19Kelly Weinersmith?

  Yeah, they're like crawling mosquitoes, but whereas mosquitoes might take blood meals from multiple different people, your lice are probably spending most of their life on you unless they jump to a partner that you have.

• 14:31Daniel Whiteson?

  Well, I still prefer lice because mosquitoes leave you with these itchy bites. And I'm always like, just take the blood meal. Don't leave me with the bite.

• 14:37Kelly Weinersmith?

  Okay.

• 14:38Daniel Whiteson?

  But lice don't give you itchy bites, do they?

• 14:40Kelly Weinersmith?

  Oh, heck, yeah, they do.

• 14:41Daniel Whiteson?

  Oh.

• 14:42Kelly Weinersmith?

  Yeah. So, OK, so lice, lice, lice bite. And depending on how your body responds to them, which is the same thing with mosquitoes,

• 14:48Daniel Whiteson?

  yeah.

• 14:48Kelly Weinersmith?

  you can get itchy. And in fact, for head lice, like, the biggest thing you worry about is that somebody is going to scratch, scratch, scratch, scratch, scratch, and then get a secondary bacterial infection. And so it's not that the lice are giving you a disease, but if you, like, create a bunch of wounds on your head from scratching, and then bacteria gets in there, that could cause its own problem.

• 15:08Daniel Whiteson?

  Right, of course. Having an itchy head is one of the biggest clues that you might have lice, of course.

• 15:13Kelly Weinersmith?

  Yeah. Yeah, right. And so whereas a mosquito takes a blood meal from you and then goes and lays her eggs somewhere else, lice take a blood meal from you, and then they cement their eggs. This is for head lice. They cement their eggs to your hair, and they stay with you. And then they hatch. And so you have a population that if you don't do anything about it over time, can multiply and become huge. Whereas one mosquito bites you, they go away. Maybe their kids will never bite you. And so I think I'd rather have a mosquito bite than a lice that might turn into a community of, of lice. Wiener Smith Manor up there or something.

• 15:50Daniel Whiteson?

  They got their own little farm. So if every species of animal has their own species of lice, and some of these species have common ancestry, did the louse species diverge at the same time as the hosts? How does that work?

• 16:03Kelly Weinersmith?

  Yeah, so, OK. So this is, this is where we get into, like, the fascinating evolutionary biology. OK, so we have two different species of lice on our body, which we've talked about. Our head lice share a common ancestor with the lice that you find on chimpanzees. So what that means is about 6 million years ago, we shared a common ancestor with chimpanzees.

• 16:24Daniel Whiteson?

  Right.

• 16:25Kelly Weinersmith?

  When we split, both of those groups that split had lice on them. And so over time, the lice on chimps ended up evolving into, like, the chimp louse. And the louse that was on, you know, what ended up becoming humans or Homo sapiens, evolved into Pediculus humanus. So which is our, our human louse. And so the common ancestor for those lice

• 16:50Kelly Weinersmith?

  Is from 6 million years ago, which is about when chimpanzees and humans split. Does that make sense?

• 16:55Daniel Whiteson?

  All right, so chimps and humans split almost 6 billion years ago. And human head lice and chimp lice split around the same time.

• 17:02Kelly Weinersmith?

  Yes.

• 17:03Daniel Whiteson?

  Okay.

• 17:03Kelly Weinersmith?

  Right.

• 17:03Daniel Whiteson?

  I'm with you so far. But there's another species of lice on humans, and we haven't explained yet where that came from.

• 17:09Kelly Weinersmith?

  That's right. And I think I want to stay on the head lice for a second and talk about what head lice can tell us about human evolution. But we will be back to the pubic lice, don't you worry.

• 17:19Daniel Whiteson?

  We will be visiting Pubic Island very shortly, but right now we're staying on the continent of the head. Okay.

• 17:24Kelly Weinersmith?

  Okay, so when you look at the head lice and you collect head lice from all over the world, you see something kind of weird, which is that there seem to be something like five or six of what they call clades, which is to say, if you look at them genetically, you're like, oh, the lice over here, they're really closely related, but the lice over here, they look different. They're not as closely related. They're not a different species. But what we think was happening was that, okay, chimpanzees and humans split, but it's not like it's a straight line to Homo sapiens, right? There was Homo erectus and Neanderthals and Denisovans. And it was really fun reading papers from before we had definitive evidence that Neanderthals and Denisovans bred.

• 18:08Kelly Weinersmith?

  And so folks might remember, we had Nathan Lentz on the show to talk about how we know from genetic evidence that humans were breeding with Neanderthals. But what they think happened is that like Neanderthals and Homo erectus and Denisovans, they all had their own lice. And for the most part, those lice were separated. So they were starting to become different species. So there was starting to become like a Neanderthal lice.

• 18:31Daniel Whiteson?

  Right.

• 18:32Kelly Weinersmith?

  And a Denisovan lice.

• 18:33Daniel Whiteson?

  So the lice populations were drifting apart the same way the human populations were, but they weren't yet so far apart, they couldn't interbreed.

• 18:40Kelly Weinersmith?

  Exactly. Right. But then Homo sapiens started breeding with these other humans, which we know happened.

• 18:46Daniel Whiteson?

  Right.

• 18:47Kelly Weinersmith?

  And so we think that some of these clades are actually like the Neanderthal lice jumping ship while the Neanderthals are going extinct. And so like some of our clades might have come from like Homo erectus who were going extinct. And we got them when we like, you know, we're sharing a bed together, probably, or I don't know, sharing hats. Who knows if we had hats back then. But so there's evidence in like, the different clades of head lice that you find around the world of the different kinds of species of humans that we sort of interacted with in our past.

• 19:19Daniel Whiteson?

  That's incredible. So we see evidence for human divergence and recombination in our own genetic heritage, and that's mirrored in the lice. That's incredible.

• 19:29Kelly Weinersmith?

  Yeah, right. And so I've seen papers that are claiming that head lice can teach us about human evolution. As far as I can tell, head lice have been able to provide additional support for what we already think is happening about human evolution. But there's been nothing in the head lice where we've like, seen something here and been like, that definitely means that humans must have done this. And then later, we found archaeological evidence for it. But still, it's nice because like, you know, you have data from one source, and you feel much better if you have data from a completely different source that's saying the same thing. And so, human head lice are helping us feel more confident about these stories about like, when our ancestors left Africa.

• 20:09Daniel Whiteson?

  Yeah.

• 20:10Kelly Weinersmith?

  And when we came back together again. And anyway, I think that's pretty awesome.

• 20:14Daniel Whiteson?

  Absolutely. And it's an important part of doing science, right? You get a story from one place, you want to see if another line of data tells the same story or a different story. And if it's different, why is that? And then there's a mystery to untangle. So it's always good to check things in different directions. And if they line up and tell the same story, then yeah, you're more confident in it. Though, of course, you could always learn new stuff.

• 20:34Kelly Weinersmith?

  That's right.

• 20:35Daniel Whiteson?

  So that's very cool.

• 20:36Kelly Weinersmith?

  Yeah. Yeah. Okay. And so now let's take a break. And when we come back, we're going to go down under. Sorry, Australians.

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• 23:08Kelly Weinersmith?

  All right, we're back, and we are moving from the head to the pubic lice.

• 23:13Daniel Whiteson?

  Right.

• 23:14Kelly Weinersmith?

  So this is where we are really digging into the question from the listener. So the hypothesis here is that, okay, we got our head lice from this common ancestor, and then we went off being humans, and over time, the population of lice that were living on us split into two different islands. The hair that we have on our head and Then the hair that we have in our pubic region and that if you can date when that split happened, that must tell you when we lost the hair around like the middle part of our body.

• 23:45Daniel Whiteson?

  Right. Although not all of us are hairless in the middle parts of their body.

• 23:50Kelly Weinersmith?

  Right.

• 23:50Daniel Whiteson?

  You know, for some of us, you could even say that there's a continuous, you know, land bridge there from one, one kind of hair to the other. Does this hypothesis rely on there being like a really distinct break there?

• 24:04Kelly Weinersmith?

  Well, so that is not where things fall apart. But that is a good point. And another point is that, you know, which we've already mentioned is that the hair in those two different locations has very different thickness and consistency. And so you find different grasping hands on the different lice in the different regions because you sort of just need different grappling hooks, depending on where you're living. But what's better evidence is the fact that actually your pubic lice are not the direct ancestors of your head lice. They are lice that we got not from a quote, co-speciation event where you and a common ancestor splits. This is a host switch. Do you want to guess where we got our pubic lice from?

• 24:45Daniel Whiteson?

  Hold on. So you're telling me that the pubic lice are not a branch of the head lice, which then drifted off because they were separated by the ocean of my belly.

• 24:54Kelly Weinersmith?

  Yep.

• 24:55Daniel Whiteson?

  But that instead they jumped from some other critter?

• 24:57Kelly Weinersmith?

  Uh huh.

• 24:58Daniel Whiteson?

  Oh, boy. Um, I'm going to guess raccoons.

• 25:03Daniel Whiteson?

  You should have seen Kelly's face. What's wrong with guessing raccoons? Raccoons have been part of human history for a long time. And

• 25:15Kelly Weinersmith?

  I don't think, I think raccoons are not like an African or Asian species. I could be wrong.

• 25:21Daniel Whiteson?

  Okay, I'm going to guess. Wait, wait, give me another guess. Give me another guess. African or Asian species rats?

• 25:27Kelly Weinersmith?

  That's a good guess, but it's gorillas.

• 25:29Daniel Whiteson?

  It's gorillas. Okay.

• 25:31Kelly Weinersmith?

  It's not a super distant ancestor, but it suggests that it, that, you know, we must have been having physical contact with gorillas. And this is not going to be that kind of show. The physical contact doesn't need to have been like dirty contact. You can imagine. Imagine that you slaughtered a gorilla to eat it and it was like in your lap while you were butchering it or whatever, but somehow we got close enough to them that their lice jumped and took up habitation in our pubic region.

• 25:58Daniel Whiteson?

  All right, but first orient me on gorillas and chimps and humans. Humans and chimps split most recently, six million years ago. Gorillas are one split back or chimps include gorillas or how does that work?

• 26:10Kelly Weinersmith?

  They're at least one split back. We're all great apes, but they're like a few splits back.

• 26:16Daniel Whiteson?

  Okay, so but the gorilla split is before the chimp split.

• 26:19Kelly Weinersmith?

  Yes.

• 26:20Daniel Whiteson?

  So you have gorilla lice and then chimp human lice and then chimp human lice split into chimp lice and human lice. And now you're saying that the gorilla lice, contrary to what we were saying earlier about how lice don't jump from species to species, this is one example of when it did. And it somehow went from some gorilla to somebody's pubic island.

• 26:39Kelly Weinersmith?

  Yes, right. So I mean, sometimes you do, you get jumps and then that species specializes. And so like, you don't find human lice typically living on gorilla now because they've become like, you know, pretty distinct, separate species.

• 26:52Daniel Whiteson?

  And so do we know when this jump happened? Like, it must have happened after humans and chimps split six or seven million years ago, right?

• 27:00Kelly Weinersmith?

  Yes. So we think it happened about three or four million years ago. As you mentioned, the split with gorillas was even farther back than six million years. And so the fact that these lice jumped onto humans three to four million years ago suggests that this is not something where the lice were like, following their ancestors, what they were doing over evolutionary time. This was just like, a jump that happened because gorillas and humans came in physical contact. Their lice, for some reason, were able to make the jump and they were like, sweet, now we're human lice.

• 27:33Daniel Whiteson?

  Right. So I have two questions about that. One,

• 27:35Kelly Weinersmith?

  Okay.

• 27:35Daniel Whiteson?

  Does that say something about the similarity between gorilla hair and human pubic hair?

• 27:41Kelly Weinersmith?

  It could.

• 27:41Daniel Whiteson?

  And number two, how do we know this happened three or four million years ago?

• 27:45Kelly Weinersmith?

  Okay, so one, I don't know, maybe, maybe gorilla hair is kind of like human pubic hair.

• 27:51Daniel Whiteson?

  I'm gonna look at gorillas pretty differently from now on.

• 27:54Kelly Weinersmith?

  Well, maybe you should. And the way that we time these things is you can find certain genes in the human body that are really important. So they shouldn't change much because if they change, it could mess up something absolutely fundamental.

• 28:09Daniel Whiteson?

  Yeah.

• 28:09Kelly Weinersmith?

  And then you look at those genes in closely related species and based on the number of spots in the sequence where there's differences, you can time how long they separated. So if there's only one spot where they're different, they probably didn't separate that long ago. But if there's like 50 spots that are different, then they probably separated a long time ago. But it's not just long time ago. We have what are called like molecular clocks, where essentially you can look at the rate at which different genes tend to pick up mutations and then back calculate how long it must have been.

• 28:45Daniel Whiteson?

  All right. So we look at gorilla lice and we compare it to human pubic lice and we see these are pretty similar. And that's why we think this jump happened. We also see there are differences. And by the number of differences, we can guess when this happened because we know how long it takes to make these differences on average.

• 29:03Kelly Weinersmith?

  Beautiful. Yep. That's right.

• 29:05Daniel Whiteson?

  Wow, that's really fascinating. So we have head lice from our common ancestor from chimps, and then pubic lice jumped over three or four million years ago. And do we think that before that, the head lice were just not in the pubic region because they were not adapted to it? Or were they all over the body and then they got outcompeted in the pubic region? For those of us who, like our common ancestors, are basically covered in hair, do we have lice everywhere? Or is it only on the head and in the pubic region? Like, does anybody have back hair lice, as sexy as that sounds?

• 29:37Kelly Weinersmith?

  Oh, yum. So, okay, so body lice are lice that tend to live in like your clothes. And so the point is that there are lice that can be like up against your back. But I think lice do well in areas where the hair is very thick.

• 29:53Daniel Whiteson?

  Yeah.

• 29:53Kelly Weinersmith?

  And well, there are some of us who have a dense land bridge between the head and the lower parts of our bodies.

• 30:02Daniel Whiteson?

  I had a roommate from New Jersey once who looked like he was wearing a sweater when he didn't have a shirt on.

• 30:08Kelly Weinersmith?

  I don't know if you had to specify that he was from New Jersey.

• 30:11Daniel Whiteson?

  He liked saying, New Jersey, only the strong survive. And I just imagined it was a veritable jungle out there.

• 30:18Kelly Weinersmith?

  Okay, all right. Well, I think for the answer is that for most people, the hair on the rest of our body is not as thick as the hair on our heads or in our pubic region. And so you do tend to have separation, but I don't know if if head lice were in the pubic region and then they were outcompeted

• 30:34Daniel Whiteson?

  Interesting.

• 30:35Kelly Weinersmith?

  by lice that could hang on better. I, yeah, that's a great quest. That's a great question. I don't know who's spending their life on that one, but I didn't find their papers.

• 30:44Daniel Whiteson?

  Well, here's another question. Maybe you don't know the answer to.

• 30:46Kelly Weinersmith?

  Okay.

• 30:46Daniel Whiteson?

  Is on a gorilla, is it the same lice all over the body? Or like, human head lice jump over to the gorilla pubic region or something crazy?

• 30:55Kelly Weinersmith?

  No, I think gorilla just have a species of lice that you find all over their body.

• 30:59Daniel Whiteson?

  Okay.

• 31:00Kelly Weinersmith?

  Okay. And so then there's this other thing that maybe you've heard. I know I've heard it a couple of times, but maybe it's not as common a misconception as I thought. But I feel like every once in a while, the pop-sai press will say, pubic lice at risk of extinction because of rise in bikini waxing. Have you heard this?

• 31:20Daniel Whiteson?

  But I love it. Are Brazilians gonna put pubic lice out of business? That's hilarious.

• 31:26Kelly Weinersmith?

  That's hilarious. And I think the answer is quite clearly no, because it would have to be a global, like,

• 31:31Daniel Whiteson?

  Ouch.

• 31:33Kelly Weinersmith?

  Exactly. We would all have to have Brazilians all at once and make sure that all of our like bed linens had been dried at like 130 degrees Fahrenheit to kill all, any pubic lice that happened to be off. Although they don't live very long off the human body. But anyway, yeah, I don't think they're at risk of extinction. I just really don't buy that. And I'm always amazed when it makes it in the press again. I'm like, come on, man. It's not like everyone is doing this.

• 31:57Daniel Whiteson?

  Take them off the endangered species list. They can survive on their own.

• 32:01Kelly Weinersmith?

  Yes, right. And I know that's like a big relief for some people. Okay. All right. So now let's jump into body lice and head lice.

• 32:10Daniel Whiteson?

  Okay.

• 32:10Kelly Weinersmith?

  Okay, so head lice and body lice have very different ways that they go about their life. So head lice tend to take lots of small meals and they tend to be smaller on average. And they just live in the hair and they cling to the hairs. Body lice spend a lot of their time living in the like nooks and crannies of your clothes and they jump onto your body to take a small number of big blood meals a day. And they also tend to be bigger. And then they retreat back into your clothes where they lay their eggs.

• 32:44Daniel Whiteson?

  All right. So body lice are a different species from head lice?

• 32:48Kelly Weinersmith?

  We thought so.

• 32:50Daniel Whiteson?

  Oh.

• 32:50Kelly Weinersmith?

  And so for a long time, we thought body lice and head lice are different. Like, they look different. They have different behaviors. And so we were like, okay, they're different. And now here is another like story you may have heard about lice. Because they're different, dating that divergence must tell you about when humans started to wear clothes.

• 33:12Daniel Whiteson?

  That would be cool.

• 33:13Kelly Weinersmith?

  That would be cool, right? And so what we know from archaeological sites is that something like 780,000 years ago, we were scraping hides.

• 33:22Daniel Whiteson?

  780,000 years ago? We're talking almost a million years ago.

• 33:27Kelly Weinersmith?

  Yeah, yeah.

• 33:27Daniel Whiteson?

  People started preparing leather clothing.

• 33:30Kelly Weinersmith?

  Ancient, well, so almost a million years ago, ancient humans were scraping hides, which could have been used as blankets. Maybe they weren't being used as clothes. We just know they were scraping hides.

• 33:41Daniel Whiteson?

  Or maybe they were being used in bullfights or something, right?

• 33:43Kelly Weinersmith?

  Yeah, right. Who the heck knows what they were being used for? Maybe they were being, they were umbrellas.

• 33:48Daniel Whiteson?

  Maybe they had parades.

• 33:49Kelly Weinersmith?

  That's right.

• 33:50Daniel Whiteson?

  Who knows?

• 33:50Kelly Weinersmith?

  Right. And floats and.

• 33:51Daniel Whiteson?

  And I remember that humans have been using tools for more than a million years. And so we're talking about like stone tools here being scraped against the skin kind of thing.

• 34:01Kelly Weinersmith?

  Probably, yes.

• 34:02Daniel Whiteson?

  All right.

• 34:03Kelly Weinersmith?

  Yeah. And then we have evidence of eyed needles. So needles that you could put a thread through from about 40,000 years ago.

• 34:10Daniel Whiteson?

  That is mind blowing.

• 34:12Kelly Weinersmith?

  I know.

• 34:12Daniel Whiteson?

  40,000 year old eyed needles? That's amazing.

• 34:15Kelly Weinersmith?

  So cool, right?

• 34:16Daniel Whiteson?

  They're made out of bone or antler or something?

• 34:18Kelly Weinersmith?

  I don't know what they're made out of, but that suggests that we were making pretty complicated clothes at that point. We weren't just like cutting a hole and sticking our arms through and it was like toga style. We were like, you know, doing something a little bit fancier at that point.

• 34:34Daniel Whiteson?

  All right, yeah.

• 34:35Kelly Weinersmith?

  Okay, so that's a pretty big gap, but we think that somewhere between 1.2 and 3 million years ago is when we started to lose our hair. And so, okay, so then the question is, can the split between body lice and head lice tell us anything, right? And so for a while, this paper came out that was going all over the place that said, it looks like the split happened about 83,000 to 170,000 years ago.

• 35:01Daniel Whiteson?

  Between body and head lice.

• 35:03Kelly Weinersmith?

  Between body and head lice. And so that could be when we started wearing clothes.

• 35:07Daniel Whiteson?

  Because wearing clothes creates this new environment for body lice to live their own way?

• 35:11Kelly Weinersmith?

  Right, because now they can live in our clothes. But, okay, so I have seen this, like, said a bunch of places, and I have probably repeated it, but we don't think that these are separate species anymore. Maybe this was a confusion looking at the different clades. So you know, remember how we were talking about how we got body lice from a lot of different places? But now we've done experiments where if you let head lice get to super high concentrations, some of them start to change their body shape and move into clothes. And so it looks like actually this is like a way that lice bodies respond to overcrowding. They move into a different environment. And so it's not different species.

• 35:53Kelly Weinersmith?

  It's like an ecology we call this phenotypic plasticity, which is to say something early in your environment tells you, hey, you need to prepare for this kind of situation. And bodies can go on like a different trajectory, like

• 36:05Daniel Whiteson?

  That's cool.

• 36:06Kelly Weinersmith?

  There are little aquatic organisms where if they can sense that there are fish in the area, they'll develop like spikes on their heads. And they can't get rid of those spikes. They'll have those spikes for the rest of their lives, but they're energetically expensive. So they only develop them when they get cues early in life that like this is the kind of environment you live in.

• 36:23Daniel Whiteson?

  So human head lice in the right situation, when the head is already overcrowded, the babies will develop a different form that's better suited to living in the clothing on the body.

• 36:34Kelly Weinersmith?

  It does seem like that is what's happening.

• 36:36Daniel Whiteson?

  And do chimp lice do that also? Or do we think this is a feature? Human lice evolved because humans were wearing clothing?

• 36:43Kelly Weinersmith?

  Yes, I would not expect that chimp lice would have something similar because they've got fur all over their bodies. It's not like they have somewhere else to switch to. And so I think we think that this is something that has to do with like living in clothes.

• 36:57Daniel Whiteson?

  And so if we could tell when human lice developed this capability, then we could date when this environment became available to the lice and learn about when humans started wearing clothing. But that doesn't seem possible. Is that possible?

• 37:11Kelly Weinersmith?

  Right. I I wouldn't know how to start there. Because I mean, because they're all interbreeding.

• 37:16Daniel Whiteson?

  Right.

• 37:17Kelly Weinersmith?

  And so, I mean, I think what's happening is that they are using genes that they already have, and they're just expressing them differently. You could maybe date it if this ability came from some like gene that got added to the population, and you could try to time when that gene got in there. But as far as I know,

• 37:36Daniel Whiteson?

  Yeah.

• 37:37Kelly Weinersmith?

  you really can't time this. And this is just like, so now we call them two different kinds of eco-morphs. And I I want to be clear. We really don't understand what's happening here very well, but we no longer think of them as separate species. It looks like head lice can become body lice, and they're interbreeding.

• 37:53Daniel Whiteson?

  Interesting. All right. And so then head lice really are whole body lice, except for the pubic region.

• 38:01Kelly Weinersmith?

  Yeah, yeah, except they so your kids, you take them to, I was gonna say lice upon a time. I cannot remember.

• 38:09Daniel Whiteson?

  Once upon a lice time.

• 38:11Kelly Weinersmith?

  Once upon a lice time? That's not what it's called, is it?

• 38:15Daniel Whiteson?

  Well, sorry.

• 38:15Kelly Weinersmith?

  Once in a lifetime.

• 38:16Daniel Whiteson?

  Yes.

• 38:16Kelly Weinersmith?

  Once in a lifetime. Okay, right. So you took your kids immediately to once in a lifetime, which means the density of head lice didn't get very high. And so they didn't jump to clothes. And so in the United States, you know, children of wealthy families like our children, the lice doesn't get that bad. But if you are someone who's unhoused and doesn't have the opportunity to change or wash their clothes for long periods of time or shower for long periods of time, it can build up and then body lice become a problem. But what has really become a problem is body lice during periods in our history where we have had concentration camps or war.

• 39:01Kelly Weinersmith?

  And in those situations, you get a lot of body lice. And one of the things that differentiates body lice from head lice is how their immune system responds to pathogens.

• 39:13Daniel Whiteson?

  Oh.

• 39:14Kelly Weinersmith?

  So when we get back, we're going to talk about how body lice have killed millions of people throughout history, whereas head lice pretty much don't.

• 39:22Daniel Whiteson?

  Wow, fascinating. All right, let's take a break. When we come back, we'll hear all about the lice wars.

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• 41:44Speaker 06

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• 41:57Kelly Weinersmith?

  And we're back. And we've talked about how head lice and body lice are very closely related, and our best guest at the moment is that body lice are just head lice that in a high-competition environment have sort of changed the way their body is shaped, and now they're living in your clothes.

• 42:15Daniel Whiteson?

  And so here Kelly is nitpicking the science for all of you.

• 42:19Kelly Weinersmith?

  That's right. That's right. And again, I want to clarify, there's a lot that we don't know. This is like the story, literally as I've been reading, like every five or 10 years worth of like literature chunks, they've been like, oh, we've kind of changed our mind about this. And so this is an evolving story, but part of why we think that body lice can transmit disease is that one of the things that differs between head and body lice is how they respond when they get infected with a pathogen and the volume of their blood meals changes. So a disease that's transmitted by body lice that has been absolutely horrible for humans in the past is called epidemic typhus.

• 42:56Daniel Whiteson?

  Sounds bad.

• 42:57Kelly Weinersmith?

  I hate the word typhus because there are three different kinds of typhuses. They're all very different and it's different than typhoid fever. So just keep in mind that there's a lot of other things that you might've heard about that are not the thing we're about to talk about right now, but epidemic typhus is what we're talking about. And it is caused by a bacteria called Rickettsia prowazekii. And Daniel's like, why did you have to say the scientific name? And Daniel, I had to say the scientific name because that is the way you can be sure that you are talking about the disease that I'm about to tell you about.

• 43:33Daniel Whiteson?

  Look, I've succeeded. I don't even need to make my objection anymore. It's already in your brain. And now I just have you questioning yourself, which is good because this means you only give us the Latin name when we actually need it. So I can retire.

• 43:47Kelly Weinersmith?

  I, well, I look forward to when you stop telling us about all the different particles and you call them particle one, two, and three. But anyway, all right.

• 43:53Daniel Whiteson?

  All right. So what does this bacterium do?

• 43:55Kelly Weinersmith?

  So this is a nasty bacteria. So the lice get infected by taking a blood meal from a human who already has the bacteria in their body.

• 44:02Daniel Whiteson?

  Okay.

• 44:03Kelly Weinersmith?

  The bacteria replicates inside of the lice and eventually is going to kill the lice also.

• 44:10Daniel Whiteson?

  Ooh.

• 44:11Kelly Weinersmith?

  And so when we talk about malaria, we talk about how the mosquito gives it to people when they bite you.

• 44:16Daniel Whiteson?

  Right.

• 44:16Kelly Weinersmith?

  And it essentially like comes out in the saliva into our body. That's not what happens here. What happens here is that the lice poop on your body or die. On your body.

• 44:26Daniel Whiteson?

  Oh.

• 44:27Kelly Weinersmith?

  And all of those bites are itchy. So you scratch and when you scratch, you scratch the bacteria, which is still present in the poop and the body parts of the lice. You scratch that into your body. Or maybe you get it on your hands and then you rub your eyes and it gets in through the mucous membranes.

• 44:43Daniel Whiteson?

  This is if I don't have the bacterium in my blood yet, but I've gotten a louse from somebody who does have it. Then it can cross back into my body through an itch I've scratched. Yikes.

• 44:53Kelly Weinersmith?

  Yeah, exactly. Right. So if, so if you borrow the coat of somebody who has lice and they gave their lice epidemic typhus. And then that lice dies on you or poops on you and you scratch. Now you've got it.

• 45:05Daniel Whiteson?

  Oh, boy.

• 45:05Kelly Weinersmith?

  And so what it does is it lives in the cells that line your blood vessels. And in particular, it tends to line the blood vessels when they get really thin. And this includes the blood vessels in your brain. So the root for typhus is a Greek word, I think, that means hazy or foggy. And that refers to the fact that it has a lot of neurological symptoms that make you sort of. I know. I know. It's the worst. And so what it's doing is it like, it's living in your blood vessels, including the ones in your brain. And it replicates and replicates and replicates until it bursts open those blood vessels.

• 45:40Daniel Whiteson?

  Oh.

• 45:41Kelly Weinersmith?

  And now you've got these leaky blood vessels.

• 45:43Daniel Whiteson?

  That sounds bad.

• 45:44Kelly Weinersmith?

  Super bad. And then your body responds by trying to clot and stop that leaking. And so now you've also got blood clots in your brain or in these other parts of your body. And so there tend to be a lot of neurological symptoms in the past. This parasite was associated with death rates up to 60%. If you survived, that was great, but a lot of people, you know, would not survive it.

• 46:08Daniel Whiteson?

  Wow. And so have there been big outbreaks of this? Is this why it's called epidemic?

• 46:13Kelly Weinersmith?

  Yes, yes.

• 46:14Daniel Whiteson?

  You shouldn't say yes so enthusiastically, Kelly.

• 46:17Kelly Weinersmith?

  Yes.

• 46:18Daniel Whiteson?

  We're talking about a lot of suffering here. Why am I laughing?

• 46:21Kelly Weinersmith?

  I'm not. Right. Yeah, right. I'm not excited about the suffering. I'm interested in the fact that pretty much none of us have heard of epidemic typhus.

• 46:29Daniel Whiteson?

  Right.

• 46:30Kelly Weinersmith?

  Because this is like a problem that doesn't bother most of us in our day to day lives anymore.

• 46:35Daniel Whiteson?

  Yeah.

• 46:36Kelly Weinersmith?

  Yay. But for example, during World War I, the Bolshevik Revolution happened. And so Lenin and the rest of his Bolsheviks were essentially starting a civil war within Russia. They didn't want to be part of World War I anymore, so they tried to pull out. The Germans sort of kept coming anyway. And so you had this civil war happening in Russia at the same time as World War I. And things were just an absolute disaster. Epidemic typhus started sweeping through. People couldn't like wash their clothes or shower regularly enough. And something like 20 to 30 million people got infected by epidemic typhus. And like two to three million people died.

• 47:15Daniel Whiteson?

  Oh, man.

• 47:16Kelly Weinersmith?

  Right, during World War I. So that was obviously not good. Another thing that's kind of a bummer from the perspective of humans having this disease is that it seems to be able to like live sort of quietly in our body for a long time. So you can be fine. And then something stressful happens and now you have a less intense version of epidemic typhus, but you have epidemic typhus again. It used to be called, I think, bereavement syndrome because this would like people who would be absolutely stressed out and devastated because someone they love died would end up having epidemic typhus essentially wake back up again and make them feel miserable all over again.

• 47:55Daniel Whiteson?

  What's the connection between stress and the disease waking up?

• 47:58Kelly Weinersmith?

  Ah, so like diseases, even like shingles. So shingles is when the chickenpox virus wakes back up again.

• 48:04Daniel Whiteson?

  Which is really bad, right?

• 48:05Kelly Weinersmith?

  Yeah. Oh, my gosh, Zach had it and he felt like he was having a heart attack. It was absolutely horrible. And so there are viruses and bacteria that can infect you when you're young. And then years later, when you get super stressed out, that can suppress your immune system. And when your immune system is suppressed, these organisms, I don't, wake back up again is a very anthropomorphic way of saying it, but they take advantage of your immune system's weakened state to essentially give you the disease all over again, or a slightly different version of the disease. So shingles is like the adult version of chickenpox.

• 48:36Daniel Whiteson?

  And that's for people who had chickenpox as a kid, right? So chickenpox parties, bad idea.

• 48:41Kelly Weinersmith?

  Well, yeah, right. Bad idea. Vaccinations for chickenpox, great idea.

• 48:46Kelly Weinersmith?

  I don't expect that my children are ever gonna have to suffer through shingles like my husband did. Or like I might have to. Who knows what awaits the future?

• 48:54Daniel Whiteson?

  Yay, chicken pox roulette. So in this case, we're talking about a disease that's in your blood, but can lay dormant. But then when you get stressed out, or you have a terrible life event, it can rear its ugly head. That's terrible. Take advantage of you when you're down.

• 49:10Kelly Weinersmith?

  Totally terrible, totally terrible. But you know, for most of us in the United States, we haven't been exposed to epidemic typhus. We haven't been in like war or refugee situations because we're very lucky in that regard.

• 49:22Daniel Whiteson?

  But why is that exactly? Is that because we just don't have very many lice? Or because the lice we do have are not infected? Or both?

• 49:30Kelly Weinersmith?

  Both. So the big thing is that your head lice don't become body lice, unless you are not showering or washing your clothes regularly.

• 49:40Daniel Whiteson?

  Right.

• 49:40Kelly Weinersmith?

  And that happens more often in situations where you're a refugee, or you're unhomed, or it's a war.

• 49:48Daniel Whiteson?

  Got it.

• 49:49Kelly Weinersmith?

  So for example, lice diseases, this one and others, including one called trench fever, was a really big problem in World War I when they were in the trenches and they like couldn't get out to shower regularly. And so the lice built up to very high numbers, the head lice became body lice, and now they're transmitting disease and you're in close quarters. So it's jumping from one person to another.

• 50:12Daniel Whiteson?

  Got it. I see.

• 50:14Kelly Weinersmith?

  But in the United States, there's a reservoir for the bacteria, which I won't say again so that Daniel doesn't get upset with me. And the reservoir are little flying squirrels.

• 50:26Daniel Whiteson?

  What?

• 50:26Kelly Weinersmith?

  Yeah. So people who interact with flying squirrels or their nests, where the lice can get left behind for a little while, are some of the rare cases of epidemic typhus that you see in the United States.

• 50:38Daniel Whiteson?

  And when you say reservoir, you don't mean like a lake out there with water we can drink? You mean someplace where the disease is like hiding out and hanging out and waiting to strike?

• 50:48Kelly Weinersmith?

  Quite so. Yes. That's right. That's right. So for the most part, we don't worry about epidemic typhus. If somebody does happen to get epidemic typhus, you can treat it with doxycycline, which is an antibiotic.

• 50:58Daniel Whiteson?

  Thank you, Big Pharma.

• 50:59Kelly Weinersmith?

  That's right. Yeah. Yep. So being in the United States is pretty great when you are able to regularly shower and wash your clothes.

• 51:06Daniel Whiteson?

  Great.

• 51:06Kelly Weinersmith?

  Hans Zinser, who's like famous for writing Rats, Lice and History, which is like a book on epidemic typhus.

• 51:12Daniel Whiteson?

  I've been itching to read that book.

• 51:14Kelly Weinersmith?

  I honestly, I don't recommend it. I like, he goes on long tirades about like art and science and they're not particularly insightful and like,

• 51:23Daniel Whiteson?

  Oh, wow.

• 51:24Kelly Weinersmith?

  You gotta get at least like 25% of the way through the book before he starts talking about typhus and you're like, get to the point. And he starts each chapter with, I'm sorry about the digression. And you're like, you should be, get to typhus.

• 51:35Daniel Whiteson?

  Sounds like the book needed an editor.

• 51:37Kelly Weinersmith?

  I know, right? And so, so anyway, he has this great quote, "Typhus will continue to break into the open whenever human stupidity and brutality give it a chance." So anyway, it happens to come along with war and refugee situations.

• 51:51Daniel Whiteson?

  That is a pretty great quote.

• 51:52Kelly Weinersmith?

  That is a pretty great quote. He does have, he's got a lot of great quotes in the book. He's got, he's got another quote about how you should feel bad because the lice give up their little ghost when they die from typhus. And so maybe you should like, not feel so bad about the lice. And if anybody wants a lot more detail on these diseases, they should check out the typhus episode on this podcast will kill you. Anyway, lots of additional great quotes in that podcast.

• 52:16Daniel Whiteson?

  I didn't mean to brush off the suffering of the lice.

• 52:20Kelly Weinersmith?

  Yeah, that's right. I don't feel as bad for lice as I do for people.

• 52:23Daniel Whiteson?

  Okay.

• 52:24Kelly Weinersmith?

  Anyway, there's also Laos-born relapsing fever. This is caused by a different kind of bacteria. It gives you fevers that kind of come and go. There's estimates that around World War I, about 5 million people died from this fever as well. And this was happening like in the trenches and stuff. And then there's trench fever, which we talked about a little bit earlier, which was a problem for the people living in trenches, but it's still a problem now in some parts of the world where lice can kind of reach high numbers. But, so we talked about how, you know, millions of people died during World War I from diseases transmitted by lice. There's another figure that goes around a lot when you're, you know,

• 53:03Kelly Weinersmith?

  reading through the lice literature, as some of us do. And, and there is a cemetery where some of Napoleon's soldiers from the Grand Armee were buried. And this was after- After they went to Moscow and were, you know, defeated by the Russian winter.

• 53:20Daniel Whiteson?

  Yeah.

• 53:21Kelly Weinersmith?

  And about a third of the dental pulp that they went through. So sometimes you can find like evidence of bacterial infections in dental pulp in skeletons. About a third of them.

• 53:32Daniel Whiteson?

  Sorry, dental pulp? This is like the inner part of a tooth or something?

• 53:35Kelly Weinersmith?

  Yeah, yeah. The inner part of the tooth. If you can like extract that and do like genetic sequencing on it, which they were able to.

• 53:42Daniel Whiteson?

  They dug up all these graves?

• 53:44Kelly Weinersmith?

  Yeah, they dug up all these graves.

• 53:45Daniel Whiteson?

  What?

• 53:46Kelly Weinersmith?

  I mean, this kind of stuff happens a lot.

• 53:48Daniel Whiteson?

  Oh, man.

• 53:48Kelly Weinersmith?

  For historic, when you're trying to study history.

• 53:50Daniel Whiteson?

  Right.

• 53:51Kelly Weinersmith?

  But anyway, they found that a third of the soldiers that were in those graves were carrying diseases transmitted by lice. And so it looks like lice might have played a role in defeating Napoleon's army in addition to the horrible Russian winters.

• 54:04Daniel Whiteson?

  Wow, amazing.

• 54:06Kelly Weinersmith?

  Yeah, but like, just to really emphasize how many people died there. Napoleon went to Moscow with half a million people, came back. You want to guess how many he came back with?

• 54:16Daniel Whiteson?

  Hmm, let's see. 20% died from lice. So I'm gonna go, I don't know, maybe 100,000?

• 54:23Kelly Weinersmith?

  3,000.

• 54:24Daniel Whiteson?

  3,000?

• 54:26Kelly Weinersmith?

  3,000.

• 54:27Daniel Whiteson?

  Don't sound so excited, Kelly. We're talking about human death here.

• 54:31Kelly Weinersmith?

  I, right, okay.

• 54:33Kelly Weinersmith?

  3,000.

• 54:36Daniel Whiteson?

  Now it sounds like you're pretending to care.

• 54:38Kelly Weinersmith?

  Well, okay, I, I care. It's, but like.

• 54:40Daniel Whiteson?

  It's dramatic. Yeah, I agree.

• 54:41Kelly Weinersmith?

  Yes, my voice is trying to convey like, just the like, mind blowingness of like, holy cow, that is so many lives. This is like, what was Napoleon doing? Anyway, history. Okay, so let's wrap things up. There have been a lot of different instances throughout history where lice transmitted diseases have killed millions of humans.

• 55:00Daniel Whiteson?

  Yeah.

• 55:01Kelly Weinersmith?

  Lucky for us today, especially if you live in a place like the United States, when you get lice, which happens to six to 12 million kids every year.

• 55:10Daniel Whiteson?

  Wow.

• 55:10Kelly Weinersmith?

  What you think is, oh, I have to go to once in a lice time again. You don't think, I hope I don't get epidemic typhus.

• 55:17Daniel Whiteson?

  But now I'm gonna think that.

• 55:19Kelly Weinersmith?

  Okay, well, your kids are old enough that hopefully they're not bringing home head lice anymore.

• 55:24Daniel Whiteson?

  No, no longer. Yeah.

• 55:25Kelly Weinersmith?

  Yeah, and. So now we we treat this with like, you know, with combs and specialized shampoos. There's an interesting new treatment that people are trying out. So lice have an endosymbiotic bacteria, so a bacteria that lives inside of them. And that bacteria is critical for providing the lice with B vitamins, which are not present in human blood. And so people are trying to explore whether or not you can use antibiotics to kill the bacteria that live inside of the lice. And if that will then kill the lice, because they need those bacteria.

• 55:58Daniel Whiteson?

  Or the lice just get like the lice version of scurvy or something?

• 56:01Kelly Weinersmith?

  Yeah, arr, this be a bad head.

• 56:08Daniel Whiteson?

  All right.

• 56:10Kelly Weinersmith?

  All right.

• 56:11Daniel Whiteson?

  All right, well, this is a fascinating dive into history. It is tragic, of course, that lice terrorize people and kill so many people. But it's also fascinating that it can tell us so much about our ancient, ancient history.

• 56:23Kelly Weinersmith?

  Or that it can confirm what we already think is happening with our ancient, ancient history. As I said, I have to be a wet blanket, but still, there's lots of interesting stuff going on here. So yes, more money to study lice.

• 56:33Daniel Whiteson?

  But they do tell us about this gorilla-human crossover event.

• 56:37Kelly Weinersmith?

  Yeah.

• 56:37Daniel Whiteson?

  Right?

• 56:38Kelly Weinersmith?

  Yeah.

• 56:38Daniel Whiteson?

  That we didn't know about before.

• 56:39Kelly Weinersmith?

  I mean, I guess you like, how interesting is it to know that humans interacted with gorillas in the past? Like, I would have guessed that we were killing and eating gorillas. You'd kill and eat whatever you need to when you're an ancient human. I don't know.

• 56:52Daniel Whiteson?

  Kelly's ancestors killed and ate gorillas all the time, it sounds like. Come on down for a gorilla barbecue at Kelly's ancestors' house.

• 57:00Kelly Weinersmith?

  Okay, all right. Well, you're all invited.

• 57:03Daniel Whiteson?

  Did you say you grew up in New Jersey? Not surprised.

• 57:06Kelly Weinersmith?

  Oh, oh, my ancestors are largely, I guess, French and Irish. And so, you know, a bunch of us might have died, you know, hiking back from Moscow with Napoleon's Grand Armee or whatever. And then during the Great Irish Famine, the Potato Famine, around like 1845, 1848, there was also a lot of deaths because of disease at that time. Like, if you are starving, you probably don't have the energy to change your clothes or shower. So epidemic typhus killed a bunch of Irish people there as well. So ancestors on both sides of my family were dying from typhus, maybe.

• 57:42Daniel Whiteson?

  She says gleefully.

• 57:45Kelly Weinersmith?

  This is just the tone of voice at which I approach everything in my life.

• 57:50Daniel Whiteson?

  You might consider having different tones or different topics, you know,

• 57:53Kelly Weinersmith?

  All right.

• 57:54Daniel Whiteson?

  Or folks out there who want a really bright eulogy, write to Kelly. She will come to your funeral and talk gleefully about your death.

• 58:01Kelly Weinersmith?

  Yes, if your funeral is a celebration of life, then invite me. If it is a

• 58:05Daniel Whiteson?

  Celebration of lice.

• 58:08Kelly Weinersmith?

  All right, we need to, we need to knock this off. It's time for us to go.

• 58:11Daniel Whiteson?

  Thanks, everybody, for taking this journey with us.

• 58:14Kelly Weinersmith?

  Until next time.

• 58:22Daniel Whiteson?

  Thanks, everybody, for listening. Please go and do us a favor and rate the show on whatever podcast app you're using. It really helps people find us.

• 58:29Kelly Weinersmith?

  Daniel and Kelly's Extraordinary Universe is edited by the amazing Matt Kesselman.

• 58:34Daniel Whiteson?

  He really is a wizard. You can also find us online on Blue Sky, Instagram, and X, D and K Universe. Come engage with us.

• 58:44Kelly Weinersmith?

  You can email us at [email protected]. We really do want to hear from you.

• 58:50Daniel Whiteson?

  And you can find our website, www.danielandkelly.org, where you'll also find an invitation to join our Discord, where everybody comes and talks about the amazing universe.

• 59:01Kelly Weinersmith?

  And we also have the most amazing moderators. This is an iHeart Podcast. Thanks for joining us.

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• 1:00:47Kelly Weinersmith?

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