WEBVTT - Hooves, Part 2 0:00:03.040 --> 0:00:06.800 Welcome to Stuff to Blow Your Mind production of iHeartRadio. 0:00:13.240 --> 0:00:15.600 Hey, welcome to Stuff to Blow Your Mind. My name 0:00:15.640 --> 0:00:16.639 is Robert Lamb. 0:00:16.840 --> 0:00:19.200 And I'm Joe McCormick, and we're back with part two 0:00:19.320 --> 0:00:22.520 of our series on the horse hoof. Now. In part one, 0:00:23.040 --> 0:00:26.400 we discussed the anatomical form of the horse hoof, with 0:00:26.440 --> 0:00:30.160 an emphasis on the alarming fact that the hoof is 0:00:30.280 --> 0:00:35.519 essentially a highly specialized form of the tetrapod middle finger. 0:00:35.680 --> 0:00:37.960 So when you see a horse galloping around, yes, it 0:00:38.080 --> 0:00:42.600 is running around on all middle fingers and toes. We 0:00:42.680 --> 0:00:45.959 talked about an ancient legend about the horse ridden by 0:00:46.040 --> 0:00:50.360 Julius Caesar, which some artists have depicted as having dock 0:00:50.479 --> 0:00:53.520 and hair and human feet instead of hoofs, at least 0:00:53.520 --> 0:00:57.560 on the first two legs. Rob's idea, I think was 0:00:57.640 --> 0:01:00.280 that this it's possible that these stories could be based 0:01:00.320 --> 0:01:04.759 on observations of what are called polydactyl horses, horses born 0:01:04.840 --> 0:01:08.120 with extra hooflets on the sides of the primary hoof, 0:01:08.160 --> 0:01:09.440 which do in fact exist. 0:01:09.840 --> 0:01:13.640 Yeah, this seems to be the more sensible interpretation that 0:01:13.680 --> 0:01:17.000 you see taken by folks, and I don't think anyone's 0:01:17.040 --> 0:01:22.360 actually arguing that these horses had like human fore feet, 0:01:23.160 --> 0:01:27.080 but it looks hilarious in the illustrations. It does. 0:01:27.160 --> 0:01:30.440 And we finally talked about the evolution of the horse hoof, 0:01:30.520 --> 0:01:34.199 with the commonly accepted narrative being that millions of years ago, 0:01:34.440 --> 0:01:38.959 the ancestors of modern horses lived in more forested environments, 0:01:39.000 --> 0:01:42.759 maybe warmer, wetter environments. They were much smaller, maybe about 0:01:42.760 --> 0:01:46.800 the size of dogs, and had multiple toes per feet. Then, 0:01:47.040 --> 0:01:51.680 due to climate and habitat changes, they became grassland dwellers, 0:01:51.720 --> 0:01:56.320 which drove them to evolve larger body sizes and select 0:01:56.360 --> 0:01:59.960 for galloping speed. And these changes coincided with the law 0:02:00.400 --> 0:02:03.520 of peripheral toes until you end up with the modern 0:02:03.560 --> 0:02:06.400 horse and its relatives in the genus equis, so that 0:02:06.400 --> 0:02:09.919 would include the zebra and the ass, all having only 0:02:10.040 --> 0:02:14.080 one toe per foot, the columnar hoof. Now today, we 0:02:14.120 --> 0:02:16.560 wanted to continue the series on the horse hoof, getting 0:02:16.560 --> 0:02:20.359 into a couple other things about horsecof evolution as well 0:02:20.360 --> 0:02:23.720 as the invention of the horseshoe. But before we do that, 0:02:24.000 --> 0:02:27.440 I wanted to take a brief detour into a metaphorical 0:02:27.480 --> 0:02:32.760 connection to the hoof, which concerns medical diagnostics, and more generally, 0:02:32.800 --> 0:02:38.279 the realm of statistical reasoning. So there's a famous aphorism 0:02:38.720 --> 0:02:43.000 widely used in medical education, often invoked by practicing physicians, 0:02:43.360 --> 0:02:46.480 and it goes like this, when you hear hoof beats, 0:02:46.639 --> 0:02:51.200 look for horses, not zebras. Rob. I think this saying 0:02:51.280 --> 0:02:53.280 may have come up on the show in the past, 0:02:53.320 --> 0:02:56.040 though I couldn't remember when, but I'm sure you've heard 0:02:56.040 --> 0:02:58.000 this before, right, Yeah. 0:02:58.160 --> 0:03:02.120 Yeah, basically is what it sounds like, right, it's, you know, 0:03:02.200 --> 0:03:05.640 whatever the evidence seems to indicate, go for the more 0:03:05.800 --> 0:03:12.239 likely and more statistically reasonable explanation for the evidence. Right. 0:03:12.400 --> 0:03:14.240 So I was looking up the history of this quote 0:03:14.240 --> 0:03:17.480 in a chapter on medical aphorisms in a book called 0:03:17.560 --> 0:03:22.280 White Coat Tails Medicine's Heroes, Heritage and Misadventures by Robert B. 0:03:22.480 --> 0:03:26.080 Taylor published by Springer. So I'll refer back to that 0:03:26.160 --> 0:03:28.200 chapter in a second. But yeah, Rob, like you said, 0:03:28.240 --> 0:03:31.160 the point of this aphorism is that when a patient 0:03:31.240 --> 0:03:35.000 presents with symptoms X, Y, and Z, you should start 0:03:35.160 --> 0:03:39.440 by thinking about the most common conditions within the population 0:03:40.000 --> 0:03:43.800 associated with that cluster of symptoms, rather than jumping to 0:03:43.880 --> 0:03:47.800 assumptions about rare diseases. So, for example, if a patient 0:03:47.880 --> 0:03:51.760 presents at a US clinic with flu like symptoms, it's 0:03:51.800 --> 0:03:54.840 better to start by investigating the possibility that they have 0:03:55.040 --> 0:03:59.520 the flu or common cold, or now maybe COVID, rather 0:03:59.560 --> 0:04:02.920 than to by investigating whether they have contracted the hindra 0:04:03.120 --> 0:04:07.560 virus from a flying fox in Australia. Taylor traces this 0:04:07.720 --> 0:04:11.440 saying back to an American medical researcher named Theodore E. 0:04:11.640 --> 0:04:14.560 Woodward who lived nineteen fourteen to two thousand and five, 0:04:15.080 --> 0:04:18.720 who taught at the University of Maryland School of Medicine. 0:04:18.920 --> 0:04:21.480 And it seems actually the common form of this aphorism 0:04:21.560 --> 0:04:25.839 might be a paraphrase, and the more accurate original quote 0:04:26.680 --> 0:04:30.960 may have been don't look for zebras on Green Street. 0:04:31.720 --> 0:04:34.160 That might be a little perplexing, but it makes sense 0:04:34.160 --> 0:04:37.800 in the context because Green Street was the location of 0:04:37.920 --> 0:04:41.039 the University of Maryland hospital in Baltimore, and he was 0:04:41.080 --> 0:04:44.159 teaching at the University of Maryland two students there, So 0:04:44.240 --> 0:04:45.800 of course you can see why it would need to 0:04:45.839 --> 0:04:49.120 be rephrased to make more sense outside of its original locality. 0:04:49.200 --> 0:04:54.680 But I also think the localization to Baltimore geography highlights 0:04:54.839 --> 0:04:58.440 something important, which is that this aphorism is only useful 0:04:58.480 --> 0:05:02.560 when you're talking about a no own population of patients 0:05:02.560 --> 0:05:06.120 in which the frequency of certain diseases or conditions is 0:05:06.240 --> 0:05:09.200 fairly well understood. Because if you were talking to a 0:05:09.200 --> 0:05:12.360 group of medical students, maybe in a region of southern 0:05:12.400 --> 0:05:15.680 Africa where zebras are abundant, it might make sense to 0:05:15.760 --> 0:05:18.760 use the aphorism inverted, I guess, depending on how many 0:05:18.760 --> 0:05:21.479 horses there are around as well. But in the same sense, 0:05:21.560 --> 0:05:23.880 you have to know what the frequencies are in the 0:05:23.920 --> 0:05:26.480 population you're looking at before deploying this. 0:05:27.640 --> 0:05:28.560 Yeah, that's true. 0:05:28.920 --> 0:05:32.080 Now, I find this the reasoning behind the saying actually 0:05:32.160 --> 0:05:34.240 kind of interesting, because if you interpret it in the 0:05:34.360 --> 0:05:37.120 usual way, it's a piece of advice that can seem 0:05:37.200 --> 0:05:41.720 rather obvious, like common explanations are more common than rare ones. 0:05:42.440 --> 0:05:46.200 But I think as a general rule, when looking for explanations, 0:05:46.680 --> 0:05:50.120 we do have to be reminded to start by considering 0:05:50.520 --> 0:05:55.000 what is most likely in terms of frequency, because there 0:05:55.000 --> 0:05:59.040 are all kinds of mental biases that constantly tempt us 0:05:59.440 --> 0:06:04.320 to start looking for highly unusual causes for unexplained phenomena 0:06:04.720 --> 0:06:09.640 before we've exhausted all of the extremely commonplace candidates for 0:06:09.720 --> 0:06:15.080 one thing. Unusual causes and explanations are usually more exciting. 0:06:15.480 --> 0:06:17.840 They kind of stick in the mind because of our 0:06:17.960 --> 0:06:21.240 level of interest in them, and they can quite easily 0:06:21.320 --> 0:06:24.279 then come to mind when we start searching around for 0:06:24.360 --> 0:06:26.960 an explanation. They're sort of at the top of the 0:06:27.000 --> 0:06:30.800 toy box right now. In this section of the book 0:06:30.839 --> 0:06:34.159 I was talking about, Taylor makes an interesting point about 0:06:34.200 --> 0:06:38.200 the zebra aphorism, which I hadn't quite considered. I was 0:06:38.240 --> 0:06:41.240 just thinking at the first order level of more common 0:06:41.279 --> 0:06:45.400 explanations and less common explanations. But Taylor also writes quote 0:06:45.480 --> 0:06:51.400 as a clinical corollary, experienced diagnosticians look first for uncommon 0:06:51.560 --> 0:06:59.200 manifestations of common conditions rather than common manifestations of uncommon diseases. 0:07:00.160 --> 0:07:03.479 Now that seemed really interesting to me. I hadn't quite 0:07:03.480 --> 0:07:05.520 thought about it that way. And of course it would 0:07:05.520 --> 0:07:08.640 depend on exactly how uncommon you mean in each clause 0:07:08.680 --> 0:07:11.160 of that sentence, Like if you were to represent them 0:07:11.160 --> 0:07:14.560 as actual percentage chances and stuff, the math might break 0:07:14.600 --> 0:07:16.920 out in different ways. But if a certain set of 0:07:17.000 --> 0:07:20.120 symptoms appears in I don't know, only three percent of 0:07:20.240 --> 0:07:23.960 cases of an extremely common condition that affects you, know, 0:07:24.080 --> 0:07:27.600 millions of people every year. It is probably still worth 0:07:27.640 --> 0:07:32.880 investigating that diagnosis, the uncommon manifestation of the extremely common 0:07:32.960 --> 0:07:36.600 condition before you look at the possibility of a condition 0:07:36.680 --> 0:07:40.400 that matches the symptoms very closely. But you know, you 0:07:40.480 --> 0:07:42.560 might only see only a couple of cases in the 0:07:42.560 --> 0:07:46.760 world per year, it's extremely rare. You'd still get way 0:07:46.880 --> 0:07:51.360 more hits of confirmation on the on the uncommon version 0:07:51.560 --> 0:07:52.640 of the common condition. 0:07:53.040 --> 0:07:55.880 It reminds me of various discussions we've had about cryptozoology 0:07:56.360 --> 0:08:02.040 and the interpretations and misinterpretations of dead animals and in 0:08:02.080 --> 0:08:06.840 some cases dead human beings, where you're looking at some 0:08:07.000 --> 0:08:09.520 rate of decay and yeah, are you looking at it 0:08:09.560 --> 0:08:13.080 as an uncommon manifestation of a common condition? In other words, 0:08:13.120 --> 0:08:15.040 are you looking at is kind of like a novel 0:08:15.720 --> 0:08:21.160 pattern or appearance in decay of just a normal, mundane animal, 0:08:21.680 --> 0:08:24.720 or are you going to jump to that extreme level 0:08:24.720 --> 0:08:27.240 and think, well, no, this is just how it looks 0:08:27.560 --> 0:08:30.480 and we've just never seen this creature before. Yeah. 0:08:30.600 --> 0:08:33.400 Yeah. However, I want to come back on the other end, 0:08:33.600 --> 0:08:38.040 because if you search for medical case reports citing this aphorism, 0:08:38.120 --> 0:08:40.560 which I was doing a lot of times, it will 0:08:40.600 --> 0:08:45.400 be specifically to discuss cases where it was a zebra 0:08:45.520 --> 0:08:49.840 on Green Street, the rare and unexpected diagnosis that turned 0:08:49.880 --> 0:08:52.880 out to be correct. So just one example I was 0:08:52.920 --> 0:08:56.800 looking at this was a case report published in Clinical 0:08:56.840 --> 0:09:00.680 Practice in Cases in Emergency Medicine in twenty nineteen by 0:09:00.760 --> 0:09:03.960 Loupez at All called Beware of the Zebra nine year 0:09:03.960 --> 0:09:07.400 old with Fever. I believe this incident took place in 0:09:07.440 --> 0:09:09.719 the US state of North Carolina. So it was a 0:09:10.080 --> 0:09:13.640 nine year old girl whose family spoke only French, and 0:09:13.720 --> 0:09:18.720 they presented at the hospital with the patient having an 0:09:18.880 --> 0:09:23.760 abdominal pain, vomiting, intermittent fevers, fatigue, and headache, and because 0:09:23.760 --> 0:09:26.199 there was a language barrier, everything had to be done 0:09:26.200 --> 0:09:28.320 with the help of an interpreter, and it seems that 0:09:28.400 --> 0:09:32.480 this led to some maybe some original misunderstandings about the 0:09:32.520 --> 0:09:36.000 case history. So the doctors tried to diagnose based on 0:09:36.080 --> 0:09:39.360 all the normal explanations that they would be likely to 0:09:39.400 --> 0:09:42.679 see in their patient population, but none of the common 0:09:42.720 --> 0:09:47.000 diagnoses really fit her case. Her condition continued to get worse, 0:09:47.040 --> 0:09:50.120 it even became life threatening, and the breakthrough seemed to 0:09:50.120 --> 0:09:53.199 come when the doctors began looking outside the normal slate 0:09:53.240 --> 0:09:56.760 of conditions encountered in their practice in the United States. Finally, 0:09:57.200 --> 0:09:59.839 they learned that the girl's family had just in the 0:09:59.840 --> 0:10:04.440 wa weeks before, arrived from the Congo, where malaria is common. 0:10:04.840 --> 0:10:08.160 The care providers eventually ordered a test that would put 0:10:08.160 --> 0:10:11.319 them on the right track. They write in their report, quote, 0:10:11.480 --> 0:10:15.080 this test was a peripheral blood smear, specifically a thick 0:10:15.120 --> 0:10:19.440 and thin smear, which revealed Plasmodium falciparum. And this is 0:10:19.440 --> 0:10:23.480 one of the protozoa responsible for causing malaria, leading to 0:10:23.520 --> 0:10:27.120 a final diagnosis of cerebral malaria. And then they write 0:10:27.280 --> 0:10:30.239 from here they contacted the twenty four hour CDC hotline 0:10:30.320 --> 0:10:36.040 to immediately get the appropriate anti malarial medication. They put 0:10:36.040 --> 0:10:38.920 the girl on a quinine drip and admitted her to 0:10:39.040 --> 0:10:42.880 the pediatric intensive care unit. And then they say, quote remarkably, 0:10:42.920 --> 0:10:45.440 within four weeks she made a full recovery and returned 0:10:45.480 --> 0:10:49.000 home with her family. So thankfully, the patient was all 0:10:49.080 --> 0:10:52.000 right in the end, but she potentially could have died 0:10:52.040 --> 0:10:56.679 if doctors hadn't made the locally unusual but correct diagnosis 0:10:56.720 --> 0:10:59.440 and given her the right treatment. And so the authors 0:10:59.440 --> 0:11:02.319 say in their conclusion quote, many of us are taught 0:11:02.360 --> 0:11:05.600 the common aphorism in medical school. When you hear hoof beats, 0:11:05.679 --> 0:11:09.000 think horses, not zebras. When approaching a nine year old 0:11:09.000 --> 0:11:11.640 with fever, we hear the hoof beat symptoms and tend 0:11:11.640 --> 0:11:14.760 to think of the typical diagnoses that are commonly seen 0:11:14.880 --> 0:11:18.160 in our pediatric population. Yet if we are not thinking 0:11:18.240 --> 0:11:21.520 about the zebras, we will miss this common presentation of 0:11:21.559 --> 0:11:24.560 a disease that is uncommon north of the equator, which 0:11:24.559 --> 0:11:28.200 could lead to high morbidity and possibly even mortality for patients. 0:11:28.960 --> 0:11:31.280 So it's very good that they were able to discover 0:11:31.360 --> 0:11:35.560 this intervene and probably save the girl's life. But it 0:11:35.640 --> 0:11:39.160 highlights how there's a difficult balance, Like if you go 0:11:39.360 --> 0:11:43.120 looking for zebras before you look for horses on Green Street, 0:11:43.320 --> 0:11:45.800 you will waste a lot of time and resources and 0:11:45.840 --> 0:11:50.240 potentially cause frequent misdiagnoses that could harm people. But if 0:11:50.240 --> 0:11:53.959 you never consider the possibility of zebras on Green Street, 0:11:54.040 --> 0:11:56.880 there will be rare but very real cases where you 0:11:56.920 --> 0:11:59.040 could save somebody's life but you don't. 0:12:00.080 --> 0:12:02.760 So that's a great point. Yeah, certainly looking at the 0:12:02.880 --> 0:12:06.360 like the professional end of the scenario, because on the 0:12:06.360 --> 0:12:08.839 other end, like say the user end and the media end. 0:12:09.320 --> 0:12:12.680 I mean, zebra on Green Street. That's a great headline. 0:12:13.160 --> 0:12:15.640 You're gonna that's this headline that's gonna stick in your mind, 0:12:16.000 --> 0:12:17.800 and then when you're going to see the doctor, you're 0:12:17.840 --> 0:12:20.720 gonna be like, hey, doc, is it possible that a 0:12:20.800 --> 0:12:23.760 rare amiba is eating my flesh? Or something to that effect, 0:12:23.840 --> 0:12:26.320 because that's what you saw in the headline, that's what 0:12:26.360 --> 0:12:31.600 you saw on the the documentary series that that that 0:12:32.200 --> 0:12:34.880 sensationalized a rare case, right. 0:12:34.920 --> 0:12:38.120 I mean, the the difficult thing is like, because of 0:12:38.160 --> 0:12:41.920 the way we emotionally react to stories like this, I 0:12:41.920 --> 0:12:44.319 feel like it kind of tends to have the effect 0:12:44.320 --> 0:12:46.320 of making us think, well, maybe then I should start 0:12:46.360 --> 0:12:51.679 looking for diagnoses of unusual diseases in patient populations. So 0:12:51.840 --> 0:12:55.520 it just highlights like diagnosis in the specific case of medicine, 0:12:55.600 --> 0:13:02.240 and searching for explanations for unknown phenomena generally is really difficult. 0:13:02.320 --> 0:13:08.080 It involves a balance between prioritizing likely explanations, which are 0:13:08.280 --> 0:13:12.000 you know, by very definition, almost always going to be correct, 0:13:12.280 --> 0:13:16.080 but also being open minded enough to catch the unusual 0:13:16.320 --> 0:13:20.040 ones when they arise. And obviously, I think a big 0:13:20.040 --> 0:13:23.320 part of the art of medicine is gaining good intuition 0:13:23.520 --> 0:13:29.920 and establishing sound processes to prioritize explanations in a reasonable 0:13:29.920 --> 0:13:33.000 way based on what we know about frequency, but then 0:13:33.120 --> 0:13:36.600 also to be able to catch the cases that are 0:13:36.760 --> 0:13:50.520 unusual and intervene appropriately to help people. All right, you 0:13:50.520 --> 0:13:52.400 want to talk a little bit about the evolution of 0:13:52.440 --> 0:13:53.079 the horse hoof? 0:13:53.480 --> 0:13:55.120 Yeah, yeah, we should probably talk a little bit more 0:13:55.160 --> 0:13:57.960 about how they came to run about in their middle fingers. 0:13:58.760 --> 0:14:02.280 We talked in the last episode about a pretty commonly 0:14:02.320 --> 0:14:06.720 accepted story of how that evolutionary process occurred, but there 0:14:06.800 --> 0:14:11.439 was still some uncertainty about exactly why the one toe 0:14:11.480 --> 0:14:14.600 making contact with the ground is favored over keeping the 0:14:15.480 --> 0:14:18.400 larger number of toes that the ancestors of horses used 0:14:18.400 --> 0:14:20.920 to have, And to some degree, I think that question 0:14:21.040 --> 0:14:23.960 is still not fully settled. There are still some questions 0:14:24.000 --> 0:14:27.280 about why exactly the one toe was favored. We do 0:14:27.440 --> 0:14:30.240 know that the ancestors of horses and zebras and asses 0:14:30.440 --> 0:14:34.680 had multiple toes per foot, But what is gained by 0:14:34.680 --> 0:14:38.520 going quad bird, you know, the middle fingers across all 0:14:38.520 --> 0:14:42.640 four feet. So the evolution of is called monodactyly having 0:14:42.680 --> 0:14:46.840 one toe Monodactyly, it has long been assumed that that 0:14:47.120 --> 0:14:51.200 was useful for allowing a large animal like a modern horse, 0:14:51.280 --> 0:14:55.000 to achieve greater running speed. But I came across an 0:14:55.040 --> 0:14:58.720 interesting alternative idea explored in a paper called the Evolution 0:14:58.880 --> 0:15:03.280 of equid monodact a review including a new hypothesis published 0:15:03.320 --> 0:15:07.600 in Frontiers and Ecology and Evolution by Christine M. Janis 0:15:07.640 --> 0:15:12.000 and Raymond Bernor. And basically here the authors ask what 0:15:12.280 --> 0:15:16.320 if the evolution of the modern equine hoof was a 0:15:16.520 --> 0:15:22.440 product of selection for endurance rather than speed, meaning that 0:15:22.560 --> 0:15:27.120 the primary advantage conferred was in the evolution of an 0:15:27.200 --> 0:15:32.200 efficient and energy efficient spring foot that would support long 0:15:32.280 --> 0:15:38.720 distance trots at medium speed to locate better food resources. So, 0:15:39.440 --> 0:15:43.600 under their hypothesis, the loss of extra toes may have 0:15:43.680 --> 0:15:47.840 been a coincidental byproduct of the selection for the more 0:15:47.880 --> 0:15:53.200 efficient spring foot, which helps the horse conserve energy while foraging, 0:15:54.240 --> 0:15:58.760 rather than an adaptation for top speed running, which again 0:15:58.840 --> 0:16:01.600 is assumed to be primarily for the purpose of escaping 0:16:01.640 --> 0:16:05.040 the jaws of predators. Now, I cite this not to 0:16:05.080 --> 0:16:08.200 say that I think their hypothesis is definitely correct. I 0:16:08.240 --> 0:16:11.640 have no expertise to decide between which explanation of the 0:16:11.640 --> 0:16:15.960 horstof evolution better fits the evidence. But this possibility made 0:16:16.000 --> 0:16:18.440 me think back again to the Zebras on Green Street 0:16:18.520 --> 0:16:23.280 saying about how sometimes certain explanations seem more likely to us, 0:16:23.400 --> 0:16:27.480 not because they're actually more common, but because they're more 0:16:27.520 --> 0:16:31.400 mentally salient. It reminds me I've talked before about this 0:16:31.640 --> 0:16:34.120 idea that I have the sort of sex and violence 0:16:34.160 --> 0:16:38.560 principle in evolutionary reasoning, where what I think I've observed 0:16:38.640 --> 0:16:43.680 is that when people without or sometimes even with biological training, 0:16:44.080 --> 0:16:47.600 are trying to think of possible evolutionary explanations for a 0:16:47.600 --> 0:16:51.280 trait in an organism, we are a little too quick 0:16:51.480 --> 0:16:57.120 to resort to explanations involving either predation or mating, and 0:16:57.240 --> 0:17:02.000 we often overlook extremely common mechanism in nature, like temperature 0:17:02.080 --> 0:17:06.600 regulation and energy efficiency, which play a huge role in 0:17:06.680 --> 0:17:09.800 the success of a life form. But I think maybe 0:17:09.840 --> 0:17:14.160 they're not as interesting to our brains as sex or violence, 0:17:14.359 --> 0:17:17.160 so we're less likely to think of them. They do 0:17:17.200 --> 0:17:19.800 not bleed, so they do not lead in the mind. 0:17:20.280 --> 0:17:22.440 Yeah, it kind of reminds me of past discussions we've 0:17:22.440 --> 0:17:26.359 talked about concerning the Stegosaurus, For example, you know, and 0:17:27.119 --> 0:17:29.520 memory serves you know that there have been various interpretations 0:17:29.520 --> 0:17:32.520 over the years, for there are those curious plates on 0:17:32.560 --> 0:17:36.200 their back, as well as very interpretations of just how 0:17:36.200 --> 0:17:40.040 they're positioned. But yeah, you can with something like that, 0:17:40.119 --> 0:17:42.760 you can. You're inevitably you're going to find those explanations 0:17:42.840 --> 0:17:47.440 that have to do with mating, or protection from predators, 0:17:47.520 --> 0:17:51.720 or protection when they're in conflict with others of their kind. 0:17:52.200 --> 0:17:56.280 But yeah, I guess sometimes these ideas that they're used 0:17:56.280 --> 0:17:59.359 for temperature regulation or something like that may may feel 0:17:59.400 --> 0:18:03.200 less excite, may feel more mundane. Though I guess you 0:18:03.240 --> 0:18:06.960 could also argue that maybe the more exotic or mysterious 0:18:07.080 --> 0:18:11.960 the feature is, like say those backridges on the stegosaurus, 0:18:12.680 --> 0:18:14.919 maybe that cancels it out to some degree. I don't know, 0:18:15.320 --> 0:18:17.560 but it's hard to imagine a like a seven year 0:18:17.560 --> 0:18:18.960 old or an eight year old playing with the toy 0:18:19.000 --> 0:18:22.600 Stegasaurus and be like, look, Mom and dad, this guy's 0:18:22.640 --> 0:18:26.120 warming up in the sun watching. That's not what bathtub 0:18:26.119 --> 0:18:27.520 dinosaurs do. They bite each other. 0:18:29.520 --> 0:18:31.200 But again, I want to make clear, I'm not saying 0:18:31.240 --> 0:18:35.119 I think that the the trotting foraging spring hoof explanation 0:18:36.000 --> 0:18:39.600 is necessarily better than the high speed running explanation for 0:18:39.640 --> 0:18:41.760 the horse hoof. I don't know, but I think it's 0:18:41.760 --> 0:18:45.840 important to remember to consider those types of explanations as well. Now, 0:18:45.880 --> 0:18:50.399 another question that has come up in several things I 0:18:50.440 --> 0:18:53.879 was reading is about should we really say that the 0:18:53.920 --> 0:18:56.480 horse only has one toe? I mean, it really does 0:18:56.600 --> 0:18:59.879 basically have only one toe that makes contact with the 0:19:00.440 --> 0:19:03.680 with the ground, But in what sense did it really 0:19:03.880 --> 0:19:07.960 quote lose the other toes. One example of this counter 0:19:08.040 --> 0:19:11.359 narrative I was reading is in an article in The 0:19:11.359 --> 0:19:15.280 New York Times by Veronique Greenwood published February eighth, twenty twenty, 0:19:15.359 --> 0:19:18.360 called a horse has five toes and then it doesn't. 0:19:18.720 --> 0:19:21.320 And this article tells the story of a researcher named 0:19:21.400 --> 0:19:25.880 Catherine Kavanaugh, a biologist at the University of Massachusetts Dartmouth, 0:19:26.280 --> 0:19:30.919 who was looking at preserved horse embryos in the lab 0:19:31.280 --> 0:19:34.760 when she discovered something very interesting, which is that during 0:19:34.840 --> 0:19:39.720 the earliest stages of gestation, the area of the embryo 0:19:39.800 --> 0:19:43.439 that will eventually develop to become the foot become the hoof. 0:19:44.320 --> 0:19:50.000 In that area, the embryonic horses have five toes. So 0:19:50.160 --> 0:19:53.040 this period during development only lasts for a couple of 0:19:53.119 --> 0:19:55.840 days before the extra toes begin to sort of fuse 0:19:55.920 --> 0:19:59.440 and vanish. But to read from the article briefly, quote 0:19:59.560 --> 0:20:03.800 the discover reimplies something profound about how anatomical development works. 0:20:04.240 --> 0:20:07.720 As an embryo puts itself together, growing from a tiny 0:20:07.800 --> 0:20:11.040 wad of cells into multiple specialized tissues, fed by blood 0:20:11.119 --> 0:20:14.679 vessels and linked by the winding threads of nerves, it 0:20:14.840 --> 0:20:18.640 is following a template. That template is subject to evolution, 0:20:19.000 --> 0:20:22.200 just like other things about the animal. But some moments 0:20:22.200 --> 0:20:25.680 in the process or some routes that development takes may 0:20:25.720 --> 0:20:30.520 not easily be altered. And so the researcher here, Catherine Kavanaugh, 0:20:30.560 --> 0:20:34.040 is quoted saying something about the early steps in toe 0:20:34.160 --> 0:20:38.360 development is stabilized. We don't know why, but that's what 0:20:38.400 --> 0:20:41.680 we think is going on. So I found this also 0:20:41.720 --> 0:20:45.480 interesting because it's an example of how stages in development 0:20:45.560 --> 0:20:50.719 can become evolutionarily fixed even when they differ from the 0:20:50.760 --> 0:20:54.520 final form. So like, for some reason, as the horse 0:20:54.640 --> 0:20:59.359 is growing as an embryo, it needs to develop five 0:20:59.560 --> 0:21:03.840 fingers before or five toes before it can lose four 0:21:03.880 --> 0:21:07.600 of the toes per hoof, so you know, eventually it 0:21:07.640 --> 0:21:10.760 will have functionally one toe making contact with the ground, 0:21:11.080 --> 0:21:14.520 but the development process has to go through this other 0:21:14.640 --> 0:21:15.560 stage first. 0:21:15.680 --> 0:21:18.960 For some reason, it reminds me of something we discussed 0:21:18.960 --> 0:21:21.280 in our whale episodes about the blowhole of the whale 0:21:21.640 --> 0:21:25.000 being seen to, of course, through the fossil record, travel 0:21:25.160 --> 0:21:26.800 up the snout up to the top of the head. 0:21:26.840 --> 0:21:29.680 But we can also observe this movement in the womb 0:21:30.040 --> 0:21:32.760 as the fetal whale is developing. 0:21:33.440 --> 0:21:38.159 Yeah. Another interesting thing about the horse hoof is that 0:21:38.240 --> 0:21:41.200 there are some people who have pointed out how vestiges 0:21:41.400 --> 0:21:44.760 of the missing toes can still sort of be found 0:21:44.840 --> 0:21:48.040 as little sort of ridges on the sides of the hoof. 0:21:48.400 --> 0:21:50.119 Yeah. I ran across this a lot in some of 0:21:50.160 --> 0:21:53.720 the veterinary sources I was looking at. 0:21:53.920 --> 0:21:56.440 But don't let this take away from your mental enjoyment 0:21:56.480 --> 0:21:59.280 of thinking about the horses running around on its middle fingers, 0:21:59.320 --> 0:22:01.160 which functionally is it is? 0:22:01.720 --> 0:22:03.600 I mean to me, it makes it even more weird. 0:22:04.040 --> 0:22:05.840 It's kind of like if you were to It's kind 0:22:05.840 --> 0:22:08.240 of like if you're looking at Kermit the frog and 0:22:08.320 --> 0:22:10.760 someone were to tell you, like there's a difference in saying, hey, 0:22:10.800 --> 0:22:14.360 there's somebody's hand in there and and someone saying, actually, 0:22:14.720 --> 0:22:16.960 all the bones of a human hand are present in 0:22:17.040 --> 0:22:20.560 Kermit the frog, but they have been repurposed and formed 0:22:20.840 --> 0:22:25.000 into the skeletal structure of this bipedal frog creature. Like 0:22:25.040 --> 0:22:27.879 that's even crazier, and I feel like that's more in 0:22:27.920 --> 0:22:30.159 line with what we know about the horses. 0:22:30.840 --> 0:22:32.000 Splendid analogy. 0:22:32.119 --> 0:22:32.520 Bravo. 0:22:33.359 --> 0:22:36.640 All right, are we ready to talk about the horse shoe? 0:22:37.080 --> 0:22:40.760 Yeah, this is something that originally I didn't think we 0:22:40.760 --> 0:22:43.080 were going to cover, or if we were to cover, 0:22:43.200 --> 0:22:45.200 we might come back, but I felt like it's kind 0:22:45.200 --> 0:22:48.399 of so closely linked to our understanding of the horse 0:22:48.440 --> 0:22:51.119 and the human use of the horse. And at the 0:22:51.160 --> 0:22:53.320 same time, in discussing this, we are going to be 0:22:53.359 --> 0:22:59.320 kind of blowing through the domestication of the horse rather quickly. 0:22:59.840 --> 0:23:02.920 Like this is a topic that has received a lot 0:23:02.960 --> 0:23:07.000 of attention over the years in varying fields. I mean, 0:23:07.480 --> 0:23:12.920 there's genetic research, there's archaeology, there's you know, various cultural inquiries. 0:23:14.240 --> 0:23:15.679 It's kind of all over the place, and there are 0:23:15.680 --> 0:23:17.880 a lot of unanswered questions about you know, especially when 0:23:17.920 --> 0:23:21.080 you get into you know, the exact who's and winds 0:23:21.160 --> 0:23:24.720 and wares, say horse domestication, and even the development or 0:23:24.720 --> 0:23:28.800 the horseshoe. But I feel like covering the horseshoe also 0:23:28.840 --> 0:23:31.879 helps us understand the hoof a little bit more so, 0:23:32.160 --> 0:23:35.800 briefly talking about the modern horse, the modern horse has 0:23:35.800 --> 0:23:39.800 a long and pivotal history as a human steed. Many 0:23:39.840 --> 0:23:43.400 animals have, of course served as mounts for human riders, 0:23:43.840 --> 0:23:47.119 and many have served as a pack and draft animals. 0:23:47.680 --> 0:23:49.920 I know that, at least on the Artifact and perhaps 0:23:49.960 --> 0:23:52.320 elsewhere in some core episodes, we've touched on the importance 0:23:52.320 --> 0:23:55.720 of the camel and the donkey, But the horse, the 0:23:55.800 --> 0:23:58.720 horse is just a whole different matter, both in terms 0:23:58.760 --> 0:24:01.240 of like the impact that it's had, like I think 0:24:01.280 --> 0:24:04.840 the larger impact that it's had globally, and also just 0:24:05.240 --> 0:24:08.959 how it has captured the imagination. Not to diminish the 0:24:09.000 --> 0:24:11.960 camel or the donkey, because in particular regions, the camel 0:24:12.000 --> 0:24:15.080 and the donkey have been far more important. Whole books 0:24:15.119 --> 0:24:17.280 have been written about the camel and the donkey, and 0:24:17.520 --> 0:24:19.719 I've read parts of them. If you want to hear 0:24:19.720 --> 0:24:21.200 a little bit more about that, go back to the 0:24:21.680 --> 0:24:24.920 Monster Fact episode that I did on Donkeys of Dune, 0:24:25.280 --> 0:24:28.520