WEBVTT - A World Before Fire: The Human Flame 0:00:03.080 --> 0:00:06.160 Welcome to Stuff to Blow Your Mind from housetop works 0:00:06.200 --> 0:00:14.680 dot com. Hey, welcome to Stuff to Blow your Mind. 0:00:14.720 --> 0:00:17.360 My name is Robert Lamb and I'm Joe McCormick in. 0:00:17.440 --> 0:00:19.239 Today is going to be part two of a two 0:00:19.280 --> 0:00:23.160 part episode about the scientific history of fire on Earth. Earth, 0:00:23.760 --> 0:00:26.640 as we learned in our last episode, probably as far 0:00:26.680 --> 0:00:29.040 as we know, the only place in the universe there 0:00:29.120 --> 0:00:31.200 is fire. Could be other places we don't know about, 0:00:31.320 --> 0:00:34.960 but here it is, right. Yeah, there are three elements 0:00:34.960 --> 0:00:36.879 required for for fire. You need the fuel, you need 0:00:36.920 --> 0:00:39.160 the heat, you need the oxygen, the tri force of fire, 0:00:39.159 --> 0:00:41.479 the tri force of fire. Earth didn't always have it, 0:00:42.040 --> 0:00:45.360 but then the conditions coalesced to where they were available, 0:00:45.360 --> 0:00:49.159 and then we had fire. And furthermore, fire, as far 0:00:49.200 --> 0:00:54.360 as we can tell, is an essential component of high technology. Yes, 0:00:54.560 --> 0:00:58.800 so you're talking about you know, creating, you know, smelting ors, 0:00:59.520 --> 0:01:03.960 creating settle towards metal tools. All of this requires that 0:01:04.040 --> 0:01:07.399 the alchemy of these creations requires fire. So it is 0:01:07.520 --> 0:01:10.640 very much clear that fire is an essential part of 0:01:10.680 --> 0:01:14.520 the technological profile of the human species on Earth, you know, 0:01:14.600 --> 0:01:18.600 beyond stone tools. Fire is how we get stuff done. 0:01:18.800 --> 0:01:20.880 But there are I mean it has symbolic power too. 0:01:20.880 --> 0:01:23.440 I mean we get in the whole idea of Promethean fire, 0:01:23.560 --> 0:01:26.080 like it's this thing that God has brought us. It 0:01:26.160 --> 0:01:28.560 is the power of power that is from beyond us 0:01:29.000 --> 0:01:32.920 that then fills us up. We talk about the fire 0:01:33.040 --> 0:01:36.280 and the spark of human existence, of the soul of compassion, 0:01:37.040 --> 0:01:40.080 all of these of these complex ideas are are are 0:01:40.200 --> 0:01:43.560 wound up in this notion of fire. Yeah. And so 0:01:43.880 --> 0:01:45.759 the first thing I think we should talk about today 0:01:45.840 --> 0:01:49.440 is is this concept of the divine spark, not so 0:01:49.520 --> 0:01:52.760 much in the theological sense, but in the literal sense, 0:01:52.800 --> 0:01:56.360 Like what what is the human brain look like on fire? 0:01:56.760 --> 0:02:00.720 What what is the fire drug done for us? And 0:02:00.760 --> 0:02:04.320 I think it's been long recognized that that control mastery 0:02:04.360 --> 0:02:07.920 over fire is one of the essential ingredients in the 0:02:08.000 --> 0:02:10.639 human animal as it exists today. One of there are 0:02:10.680 --> 0:02:14.960 things that really makes a stand apart um alongside language. Right, 0:02:15.000 --> 0:02:17.240 if you had to pick just two things that really 0:02:17.280 --> 0:02:20.280 make humans different than all the other animals, give me 0:02:20.360 --> 0:02:22.880 fire and give me some words to talk about fire with, 0:02:23.320 --> 0:02:27.080 right to to say while we're setting you on fire. Yeah, 0:02:27.080 --> 0:02:29.320 But even and this idea goes back a long way 0:02:29.360 --> 0:02:31.920 so Charles Darwin wrote in The Descent of Man in 0:02:32.040 --> 0:02:37.280 eight quote the speaking of Humankind quote, he has discovered 0:02:37.320 --> 0:02:40.480 the art of making fire, by which hard and stringy 0:02:40.600 --> 0:02:45.239 roots can be rendered digestible and poisonous roots or herbs innocuous. 0:02:45.720 --> 0:02:49.120 This discovery of fire probably the greatest ever made by man, 0:02:49.160 --> 0:02:53.480 accepting language, dates from before the dawn of history. I 0:02:53.520 --> 0:02:56.160 think we can all agree on that, right, fire comes 0:02:56.200 --> 0:03:00.919 before history. But exactly how long before history? And one 0:03:00.919 --> 0:03:02.799 thing you might be surprised to learn is that this 0:03:02.880 --> 0:03:07.400 is not a settled question. Exactly when fire emerges in 0:03:07.520 --> 0:03:11.320 human history is still up for debate. Yeah. The predictions 0:03:11.680 --> 0:03:15.120 vary from a brown from a near forty thousand years 0:03:15.120 --> 0:03:19.080 ago to four hundred thousand, five hundred thousand, or even 0:03:19.080 --> 0:03:22.440 in the in the very extreme cases one point six. Yeah, 0:03:22.520 --> 0:03:25.360 and so they're all over the map. I looked at 0:03:25.400 --> 0:03:29.360 one paper by A. J. A. J. Gaulet, who is 0:03:29.400 --> 0:03:33.480 an anthropologist and archaeologists called the discovery of fire by 0:03:33.520 --> 0:03:38.200 humans a long and convoluted process in philosophical Transation Transactions 0:03:38.200 --> 0:03:41.640 of the Royal Society b from sixteen and he looks 0:03:41.680 --> 0:03:44.920 over a lot of the evidence and says so much 0:03:45.000 --> 0:03:49.000 archaeological investigation into the emergence of fire has been very 0:03:49.040 --> 0:03:52.160 focused on the search for hearths, right, this is this 0:03:52.200 --> 0:03:54.440 is the big thing you want to find as evidence 0:03:54.520 --> 0:03:58.840 of of hominins using fire, is these fireplaces. Hearths a 0:03:58.880 --> 0:04:01.320 place where you put all your fuel together and you'd 0:04:01.360 --> 0:04:05.560 burn it. Evidence for hearts seems to appear around zero 0:04:05.600 --> 0:04:08.360 point seven to zero point four million years ago, or 0:04:08.400 --> 0:04:10.400 I guess we could just say four hundred thousand, seven 0:04:10.480 --> 0:04:14.960 hundred thousand years ago, But that's not necessarily the earliest 0:04:14.960 --> 0:04:18.360 emergence of fire use among humans. That's just when we 0:04:18.480 --> 0:04:22.920 start finding these fireplaces. In fact, evidence of burning, Galllet 0:04:22.960 --> 0:04:26.960 says appears at archaeological sites starting around one point five 0:04:27.040 --> 0:04:30.520 million years ago. But it's it's kind of difficult because 0:04:31.240 --> 0:04:35.640 just using fire doesn't necessarily always leave good evidence that 0:04:35.720 --> 0:04:38.280 can be found, you know, more than a million years later, 0:04:38.680 --> 0:04:40.720 So you really have to be on the lookout for 0:04:40.800 --> 0:04:43.120 things that are difficult to find, and they might not 0:04:43.240 --> 0:04:45.599 always leave a trace at all. Yeah, Like as with 0:04:45.640 --> 0:04:47.240 a lot of things in the fossil record, in the 0:04:47.320 --> 0:04:50.240 archaeological record, it's kind of a crap shoot as to 0:04:50.320 --> 0:04:52.840 whether it's actually going to be preserved and then if 0:04:52.839 --> 0:04:55.440 it's preserved, it's going to be discovered. Right. But so 0:04:55.600 --> 0:04:58.120 Galllet says that, you know, one way to think about 0:04:58.120 --> 0:05:00.560 it might be that it's not just that we had 0:05:00.640 --> 0:05:02.480 fire and then we didn't. But there's sort of a 0:05:02.520 --> 0:05:06.760 three stage process for the human acquisition of fire. And 0:05:06.960 --> 0:05:11.840 uh so Gallant says, first, what about fire foraging? So 0:05:12.040 --> 0:05:15.640 fire foraging is is an interesting first step in the 0:05:15.640 --> 0:05:20.279 acquisition of fire because it doesn't require the control of fire, 0:05:20.839 --> 0:05:23.359 just an attraction to it. So what would you have 0:05:23.400 --> 0:05:26.000 in mind if you hear the words fire foraging? You're 0:05:26.040 --> 0:05:29.480 going around looking for fire, not exactly your or you 0:05:29.560 --> 0:05:32.720 might be following fire around, but instead you go to 0:05:32.800 --> 0:05:35.200 a place where a wildfire has burned, and then you 0:05:35.360 --> 0:05:39.640 gain the chance for a bonus of free resources. I 0:05:39.720 --> 0:05:42.000 kind of think about it how like if you're ever 0:05:42.040 --> 0:05:44.760 in a video game like Legend of Zelda, and you 0:05:44.760 --> 0:05:47.159 go around and you like burn a bunch of bushes 0:05:47.520 --> 0:05:50.000 or something, and then under the bushes there might be 0:05:50.040 --> 0:05:53.560 some rupees or some goodies something to find there. This 0:05:53.640 --> 0:05:55.240 is kind of what that is like. So you go 0:05:55.279 --> 0:05:58.360 to a place where wildfire is burning and there might 0:05:58.440 --> 0:06:01.880 be bird eggs or rodents or lizards or other small 0:06:01.960 --> 0:06:05.320 animals exposed that you can eat, and it might also 0:06:05.640 --> 0:06:09.440 render these So it renders these resources more visible obviously 0:06:09.480 --> 0:06:13.080 because it eliminates cover easier to obtain and possibly also 0:06:13.200 --> 0:06:17.000 more digestible by accidental cooking. But there's a reason that 0:06:17.040 --> 0:06:20.480 early humans and and hominids would have been drawn to 0:06:20.600 --> 0:06:22.240 a blaze. They would have seen the smoke on the 0:06:22.279 --> 0:06:25.360 horizon really through some sort of wildfire scenario going on, 0:06:25.720 --> 0:06:28.479 and they would have sought it out from sources. Yeah. Yeah, 0:06:28.520 --> 0:06:31.000 And we can talk about some modern analogies to how 0:06:31.040 --> 0:06:35.240 these these creatures may have uh felt about fire by 0:06:35.279 --> 0:06:38.960 looking at some some modern primates today, but we'll talk 0:06:39.000 --> 0:06:41.840 about that later in the episode. And just for analogies 0:06:41.880 --> 0:06:44.560 in non human animals in nature, there are other animals 0:06:44.560 --> 0:06:46.800 that do this there, for example, birds that are known 0:06:46.839 --> 0:06:51.039 as fire followers. You know, fire foraging among avians makes 0:06:51.040 --> 0:06:52.840 it seem like it could easily have been done by 0:06:53.560 --> 0:06:57.640 hominins a long time ago too. But then so Gablet 0:06:57.800 --> 0:06:59.640 also says, you know, you've got a couple of stages 0:06:59.680 --> 0:07:03.960 after fire foraging. You've got he says, quote social slash 0:07:04.040 --> 0:07:08.400 domestic hearth, fire for protection and cooking. Okay, so you 0:07:08.560 --> 0:07:11.640 have a fire that you can gather around, there's warmth, 0:07:11.720 --> 0:07:15.120 there's light, and there is there's heat for cooking food. 0:07:15.480 --> 0:07:19.120 And then third, finally, fires used as tools in the 0:07:19.160 --> 0:07:24.280 technological processes like firing pottery or making metal tools or 0:07:24.840 --> 0:07:28.680 things like that are creating a you know, adhesives on 0:07:28.800 --> 0:07:31.680 things that take fire to make. But I think that 0:07:31.720 --> 0:07:34.720 thing about fire foraging is an interesting first step because 0:07:34.760 --> 0:07:37.480 it sort of shows you how you could maybe bridge 0:07:37.560 --> 0:07:42.360 the gap between a primate species that doesn't understand anything 0:07:42.400 --> 0:07:45.440 about fire and one that starts to use fire. You know, 0:07:45.520 --> 0:07:47.679 you don't have to go just straight from being afraid 0:07:47.680 --> 0:07:51.240 of fire to using it. Technologically, you sort of have 0:07:51.320 --> 0:07:55.080 this bridge, right, a behavioral bridge from one to the other. Yeah. 0:07:55.120 --> 0:07:57.960 One is tempted to make an analogy to the taming 0:07:58.000 --> 0:08:01.080 of a wild animal. At first, you know, you know 0:08:01.160 --> 0:08:03.040 what it is, you learn, you learn to be a 0:08:03.080 --> 0:08:04.880 little more comfortable around it, you know what kind of 0:08:04.920 --> 0:08:08.120 distance to give it, uh, how much space needs to 0:08:08.120 --> 0:08:10.760 be between you and the animal. And then eventually you 0:08:10.760 --> 0:08:13.040 get to the point where you have worked out a 0:08:13.080 --> 0:08:16.080 relationship with the animal, you have tamed it, and that's 0:08:16.120 --> 0:08:17.840 sort of what happens with fire over time. So you 0:08:17.840 --> 0:08:21.440 can imagine going from simply seeking out the fire, keeping 0:08:21.440 --> 0:08:23.160 a distance from the fire because you know that even 0:08:23.200 --> 0:08:28.040 though it it unwraps these resources for you, it itself 0:08:28.240 --> 0:08:31.000 is hot and burns you. And then over time you 0:08:31.240 --> 0:08:33.440 become comfortable enough with it to start playing with a 0:08:33.440 --> 0:08:35.880 little bit, sticking sticks into it, and then eventually even 0:08:35.960 --> 0:08:39.880 capturing portions of it and figuring out ways to utilize it. 0:08:40.040 --> 0:08:42.760 This is an interesting thing to think about. Commonly, it 0:08:42.840 --> 0:08:46.800 is very common. I bet you listening right now have this, 0:08:47.000 --> 0:08:50.280 have had this experience. It is extremely common for humans 0:08:50.320 --> 0:08:54.000 to want to play with fire. I I know, I 0:08:54.040 --> 0:08:56.440 feel this feeling like there's a there's a campfire, and 0:08:56.480 --> 0:08:58.280 you just feel this urge to kind of like poke 0:08:58.360 --> 0:09:00.559 at it with a stick or something. That I had 0:09:00.559 --> 0:09:04.080 this experience with my my son recently at a a 0:09:04.160 --> 0:09:07.240 fall celebration with some family. Uh, they had a camp 0:09:07.320 --> 0:09:11.320 fire set up and we had some sticks with marshmallows, 0:09:11.720 --> 0:09:14.479 and you know, instructed him on how to cook the marshmallow. 0:09:14.520 --> 0:09:16.120 But then I at the end of it, I said, 0:09:16.360 --> 0:09:18.080 now you can just poke the stick around in the fire, 0:09:18.120 --> 0:09:20.520 because I know that's really having been a little boy myself, 0:09:20.960 --> 0:09:23.760 and still having that little boy within me. I know 0:09:23.840 --> 0:09:25.439 that that's really what we want to do. We don't 0:09:25.440 --> 0:09:27.000 want to cook the marshmallows so much as we're going 0:09:27.040 --> 0:09:30.200 to just poke the ever loving hell out of that fire, 0:09:30.520 --> 0:09:33.360 you know, and watch the sparks rise up and watch 0:09:34.320 --> 0:09:37.560 coal's collapse and that, I mean, that's the experience. But 0:09:37.640 --> 0:09:40.000 I feel like this is something that's not just like 0:09:40.040 --> 0:09:44.000 a like a cognitively obtained behavior like using an an 0:09:44.000 --> 0:09:47.760 Excel spreadsheet might be. It feels instinctual, right, and it 0:09:47.800 --> 0:09:50.080 certainly does to me. I think you would report if 0:09:50.120 --> 0:09:53.559 small children seem to do it without prompting. There's this 0:09:53.720 --> 0:09:57.760 this instinctual draw to play with fire. Why on earth 0:09:57.760 --> 0:10:00.400 would that be an instinct? I mean, instinct is generally 0:10:00.440 --> 0:10:04.200 something that has been selected for by evolution, So why 0:10:04.200 --> 0:10:07.960 would evolution favor this instinct to go mess around with 0:10:08.040 --> 0:10:10.880 something that could burn you or even kill you unless 0:10:10.880 --> 0:10:13.560 there's some kind of compensating benefit, And it seems like 0:10:13.600 --> 0:10:16.680 for humans there probably has been, right because you compared 0:10:16.720 --> 0:10:19.680 it to taming an animal. We haven't just tamed an animal, 0:10:19.720 --> 0:10:23.080 we have tamed a demon. Right, Yeah, one is it 0:10:23.120 --> 0:10:26.480 wants them to think of the gin that has a 0:10:26.520 --> 0:10:30.280 fire that like a genie that one has has captured 0:10:30.360 --> 0:10:33.040 and and and enslaved for your own purposes. Pretty much 0:10:33.040 --> 0:10:35.680 with the fire demon in uh Was, which was the 0:10:35.679 --> 0:10:39.240 Miyazaki movie with the fire demon not spirited away but 0:10:39.720 --> 0:10:43.680 how's moving castle? Oh yeah, I remember that one. Yeah, 0:10:43.720 --> 0:10:45.240 I think that's that's a good fire demon. It's a 0:10:45.240 --> 0:10:46.880 good fire demon. Yeah, and they put him to work. 0:10:47.120 --> 0:10:49.800 But it but it also, like a gin, grants your wishes, right, 0:10:50.360 --> 0:10:52.080 So let's let's take a moment to think about some 0:10:52.160 --> 0:10:55.439 of the wishes that have been granted by the demon fire. Um. 0:10:55.600 --> 0:10:57.360 Some of these we've touched on already. If we called on, 0:10:57.400 --> 0:10:58.880 do we have to phrase them in a way that 0:10:58.920 --> 0:11:02.240 they can't come back to it? Us? Um No, because 0:11:02.280 --> 0:11:04.680 fire does come back to bite if there's no there's 0:11:04.720 --> 0:11:08.640 no avoiding that make me a cheese sentimatech So, first 0:11:08.679 --> 0:11:11.600 of all, the ability to cast light upon an uncertain, 0:11:11.720 --> 0:11:15.240 frightening and death filled night. Yeah, I mean think back 0:11:15.280 --> 0:11:17.480 to I think of this anytime around the campfire. Just 0:11:17.480 --> 0:11:20.960 think of like the primordial environment. You're huddled around this light, 0:11:21.080 --> 0:11:23.920 this heat source, and then it's gives you the ability 0:11:23.960 --> 0:11:26.280 to cast light on a world it's full of dangers, 0:11:26.679 --> 0:11:30.920 human dangers as well as predators, as well as just 0:11:30.960 --> 0:11:34.080 the problem of you tripping over a root and dying 0:11:34.160 --> 0:11:38.040 in the night and then being consumed by predators. One 0:11:38.080 --> 0:11:41.400 thing is, without fire, you can just pretty much bet 0:11:41.440 --> 0:11:45.360 that humans would not exist at certain latitudes, right right, Yeah. 0:11:45.400 --> 0:11:48.800 Fire gives us the ability to warm ourselves in increasingly 0:11:48.840 --> 0:11:51.720 colder environments, so you're no longer forced to range south 0:11:51.760 --> 0:11:56.640 in the winter or to stick to natural refuges of 0:11:56.880 --> 0:11:59.960 thermal springs. That's uh, that's something that I remember coming up, 0:12:00.080 --> 0:12:03.000 been studying saunas before. Like the long history of our 0:12:03.040 --> 0:12:06.520 association with with geothermal vents is that like these were 0:12:06.960 --> 0:12:12.200 these were little uh redoubts of of heat and civilization 0:12:12.320 --> 0:12:17.360 that early people could could range between. Interesting. But with fire, 0:12:17.640 --> 0:12:21.079 you can create your own little redoubt of warmth anywhere 0:12:21.120 --> 0:12:26.040 you want to, uh, in a in an increasingly chilly environment. Now, 0:12:26.080 --> 0:12:27.800 a big one to come back to that cheese sandwich, 0:12:27.840 --> 0:12:32.920 you mentioned the ability to externalize human digestion through the 0:12:33.000 --> 0:12:35.200 use of cooking. Like, that's that's one way I like 0:12:35.240 --> 0:12:37.000 to think of of of cooking, you know, because it's 0:12:37.000 --> 0:12:39.600 more than just oh, I put some char in this cheese, 0:12:39.600 --> 0:12:42.360 and now it's it's what's wonderful, and it is wonderful, 0:12:42.559 --> 0:12:45.559 But it goes far beyond that. Cooking makes char on cheese? 0:12:45.679 --> 0:12:49.520 Is that wonderful char on steak? Don't? Well? Maybe not char. 0:12:50.320 --> 0:12:52.839 You've had cheese sticks, right, and you know where the 0:12:52.920 --> 0:12:55.240 cheese comes off, the grilled cheese, and it kind of 0:12:55.280 --> 0:12:58.080 hardens into this you know what, I doubted you, but 0:12:58.160 --> 0:13:01.640 now I know you know what, You're tough. That's that's delicious. However, 0:13:01.800 --> 0:13:04.160 it doesn't really break down like the core benefits of 0:13:04.440 --> 0:13:06.560 cooking fairly man, because a lot of those come down 0:13:06.559 --> 0:13:10.160 to meat. Uh. Cooking meat makes it easier to digest, 0:13:10.360 --> 0:13:13.240 It reduces the cost of meat digestion. Just coming at 0:13:13.240 --> 0:13:17.400 it from you know, an economic bio energy standpoint, It 0:13:17.480 --> 0:13:22.440 compromises the structural integrity of the tissue by gelatinizing the collagen. 0:13:22.840 --> 0:13:26.760 Cooking also cleanses foods. It destroys parasites, pathogens, and even 0:13:26.760 --> 0:13:32.360 renders many natural toxins harmless. Poison fruits become foods, etcetera. Okay. 0:13:32.360 --> 0:13:36.040 On top of this, fire enables the transformation of resources 0:13:36.040 --> 0:13:38.640 such as raw or into weapons, which can then be 0:13:38.720 --> 0:13:43.040 used for your hunt. Uh. Fire eventually fuel the Industrial Revolution. 0:13:43.080 --> 0:13:45.559 The burning of fossil fuels propelled us into the modern age, 0:13:45.559 --> 0:13:48.760 into the space age. Even so, if if man looms 0:13:48.880 --> 0:13:52.319 large uh in a in a grand scheme of things, 0:13:52.520 --> 0:13:55.520 it's because the demon fire stands about behind it, casting 0:13:55.520 --> 0:13:59.160 a shadow across the world and beyond, as Rocky Aerrison 0:13:59.160 --> 0:14:03.520 would say, and for the fire demon. Yeah. And so 0:14:04.160 --> 0:14:07.360 one particular aspect of what you just talked about I 0:14:07.360 --> 0:14:10.640 want to look at is cooking, cooking as a feature 0:14:11.000 --> 0:14:15.120 of the history and development of the human species. So 0:14:15.440 --> 0:14:19.680 there is a Harvard primatologist named Richard Wrangham and also 0:14:19.760 --> 0:14:23.880 a Harvard biologist Rachel Carmody, and they've put forward this 0:14:23.960 --> 0:14:27.800 interesting hypothesis I was reading about about how cooking by 0:14:27.840 --> 0:14:32.640 way of harnessing of fire made us into the humans 0:14:32.680 --> 0:14:35.560 we are today. And so this is not considered proven. 0:14:35.640 --> 0:14:37.760 There are arguments made against it, but I think it's 0:14:37.760 --> 0:14:42.400 really interesting and worth taking a look at. So how 0:14:42.440 --> 0:14:45.040 could cooking make us into the creatures we are today? 0:14:45.120 --> 0:14:48.560 Especially from a mental point of view. Well, one thing 0:14:48.600 --> 0:14:51.160 to think about is how your body at a total 0:14:51.240 --> 0:14:54.880 state of rest is just a vampire. It is absolutely 0:14:55.080 --> 0:14:58.920 energy ravenous, and I think sometimes people don't realize how 0:14:59.000 --> 0:15:02.960 much energy is burned just by being alive, just by 0:15:03.000 --> 0:15:07.800 the steady processes like circulation, digestion, and homeostasis. So I 0:15:07.840 --> 0:15:10.840 put together an example just to illustrate how much energy 0:15:10.880 --> 0:15:13.800 this takes comparatively, uh, and I used a couple of 0:15:13.840 --> 0:15:16.680 calorie counters provided by the Mayo Clinic and Runners World 0:15:16.680 --> 0:15:18.960 websites with you know, so take this with the warning 0:15:19.040 --> 0:15:21.920 that these types of apps offer sort of general estimates 0:15:21.920 --> 0:15:24.320 shouldn't be taken as perfect or exact, but based on 0:15:24.360 --> 0:15:27.720 this imagine you are a thirty year old female who 0:15:27.840 --> 0:15:31.040 is five ft six and weighs a hundred and forty 0:15:31.040 --> 0:15:35.120 five pounds. You burn a hundred about seventeen fifty calories 0:15:35.160 --> 0:15:37.880 a day at rest, one thousand and seven fifty calories 0:15:37.920 --> 0:15:41.080 doing nothing. If you just lie in bed and watch 0:15:41.360 --> 0:15:43.560 what would you watch all day? A very low energy 0:15:43.640 --> 0:15:47.440 thing to watch on TV? I don't know, Buffy watching Buffy. 0:15:47.480 --> 0:15:50.960 Just watch Buffy all day. Now, to burn that same 0:15:51.000 --> 0:15:54.400 amount of energy through exercise, a hundred and forty five 0:15:54.400 --> 0:15:58.600 pound adult would have to run about sixteen miles at 0:15:58.640 --> 0:16:01.280 a pace of six miles per hour. The entire time. 0:16:01.680 --> 0:16:05.680 That's more than half of a marathon race. So I 0:16:05.720 --> 0:16:08.480 don't know, it just doesn't seem like laying there watching 0:16:08.520 --> 0:16:11.360 Buffy all day is about the same amount of energy 0:16:11.440 --> 0:16:14.080 work as running more than half of a marathon. But 0:16:14.200 --> 0:16:16.080 it is. Yeah, It's kind of like when you look 0:16:16.120 --> 0:16:19.280 at like business expenses and look at the sheer costs 0:16:19.280 --> 0:16:22.920 of just keeping the lights on the overhead, the overhead 0:16:22.960 --> 0:16:26.400 of a picul of business, the overhead for business human 0:16:26.680 --> 0:16:31.200 is uh is pretty staggering. Yeah, and so what are 0:16:31.400 --> 0:16:34.200 what where is all that energy going? Well, it's like 0:16:34.240 --> 0:16:36.000 we said, it powers a lot of different things that 0:16:36.080 --> 0:16:40.840 power circulation, digestion, respiration. But one of the most energy 0:16:40.920 --> 0:16:43.960 hungry organs in the human body, maybe the most energy 0:16:44.000 --> 0:16:47.640 hungry I've seen different claims about that, UH is the brain. 0:16:48.080 --> 0:16:50.640 So despite being only a very small percentage of the 0:16:50.680 --> 0:16:52.840 average human body weight, I think I've seen some like 0:16:52.920 --> 0:16:56.840 two percent or so, it regularly uses around a fifth 0:16:57.040 --> 0:17:01.040 of the body's total available metabolic energy. Of twenty of 0:17:01.080 --> 0:17:04.080 all the energy your body uses is going to the brain. 0:17:04.160 --> 0:17:07.200 I'll lighten up those synapses, things going back and forth. 0:17:07.720 --> 0:17:10.960 And according to one study I read from n each 0:17:11.200 --> 0:17:15.119 unit of brain tissue. So that's unit by mass uses 0:17:15.200 --> 0:17:19.840 about twenty two times the amount of metabolic energy that 0:17:19.960 --> 0:17:23.480 is used by the equivalent amount of muscle tissue. Being 0:17:23.560 --> 0:17:28.240 smart is very costly from an energy perspective, and we 0:17:28.359 --> 0:17:33.800 know that all organisms live in a very tight energy economy. Right, Yeah, 0:17:33.800 --> 0:17:35.640 there's not a lot, there's not room for a lot 0:17:35.640 --> 0:17:38.920 of wasted effort or even any wasted effort really when 0:17:38.960 --> 0:17:42.440 it comes to an organism. Right. Uh, so we know now, 0:17:42.720 --> 0:17:46.240 we know that the brain needs a large amount of 0:17:46.359 --> 0:17:49.720 energy in order to be powerful and formidable and intelligent, 0:17:49.880 --> 0:17:52.320 like a big primate brain is. But if you go 0:17:52.400 --> 0:17:56.640 back a few decades, scientists noticed this curious fact. So 0:17:57.160 --> 0:18:00.840 they said, when you look across species with varying rates 0:18:00.880 --> 0:18:04.879 of what's called encephalization, meaning you know, investing evolutionarily in 0:18:04.920 --> 0:18:10.440 a large, powerful brain blowing the head up, incephalized mammals 0:18:10.720 --> 0:18:14.879 don't seem to show a corresponding increase in their basal 0:18:14.960 --> 0:18:19.240 metabolic rate. So you make a bigger brain, but you're 0:18:19.280 --> 0:18:21.880 in you're investing in this energy hungry organ but you're 0:18:21.920 --> 0:18:25.480 not showing greater energy needs than a similar sized animal 0:18:25.560 --> 0:18:30.280 that doesn't invest in encephalization. So for a for a comparison, 0:18:30.280 --> 0:18:32.000 it's kind of like if you have two families that 0:18:32.040 --> 0:18:34.320 live next door to one another, and you know they 0:18:34.400 --> 0:18:37.520 both have the same income, and suddenly one of the 0:18:37.560 --> 0:18:40.880 families buys a yacht. So you're kind of thinking, how 0:18:41.040 --> 0:18:43.520 where did that want for that? Yeah, what's this other 0:18:43.760 --> 0:18:46.439 line of revenue that is that is enabling them to 0:18:46.520 --> 0:18:49.280 make this purchase? Right, So, there was a big influential 0:18:49.320 --> 0:18:53.679 paper in nineteen that offered a potential solution to this, 0:18:53.800 --> 0:18:56.920 a hypothesis to explain this, and it was known as 0:18:56.960 --> 0:19:01.119 the expensive tissue hypothesis. This was by A. Leslie C. I. 0:19:01.440 --> 0:19:06.200 L Oh and Peter Wheeler in Current Anthropology. And so 0:19:06.520 --> 0:19:08.679 what they said is one way you could pay for 0:19:08.720 --> 0:19:12.000 the brain would be to cut investments in other quote 0:19:12.000 --> 0:19:16.399 expensive organs, such as the gut. Right, So, a powerful, 0:19:17.000 --> 0:19:21.240 costly digestive system is required if you want to get 0:19:21.240 --> 0:19:25.560 the maximum energy out of bad food. Essentially, so if 0:19:25.560 --> 0:19:30.280 you've got raw, tough, hard to digest, low quality foods, 0:19:30.680 --> 0:19:33.639 you need a big, powerful gut to get all the 0:19:33.760 --> 0:19:36.800 energy out of them. But if you can imagine an 0:19:36.920 --> 0:19:41.280 organism could convert most of its diet away from all 0:19:41.320 --> 0:19:45.720 of that junk into high quality, high nutrition, easy to 0:19:45.880 --> 0:19:49.359 digest foods. Then it could cut what it invests in 0:19:49.400 --> 0:19:52.600 the gut and the digestive system, and I'll and get 0:19:52.760 --> 0:19:55.760 cut down that budget and invest all of those savings 0:19:55.880 --> 0:20:00.000 into the brain. So the original proponents of the expensive 0:20:00.000 --> 0:20:02.840 tissue hypothesis, they were focused on meat to Their idea 0:20:02.960 --> 0:20:05.360 is that you know, these hominins converted a large part 0:20:05.359 --> 0:20:08.320 of their diet from tough, hard to digest plant matter 0:20:08.480 --> 0:20:11.640 over to meat and animal products, and they could get 0:20:11.680 --> 0:20:14.600 more nutrition with less work for the digestive system. I 0:20:14.640 --> 0:20:17.800 can imagine that the TV advertisement for for meat at 0:20:17.800 --> 0:20:22.560 the time. Yea more bang for your bite, get smart 0:20:22.640 --> 0:20:25.560 quick with meat. Right. It sounds like a fallout kind 0:20:25.560 --> 0:20:29.159 of yeah. But so here's where Rangum and Carmody, That 0:20:29.240 --> 0:20:32.000 where their hypothesis comes in. What if instead of just 0:20:32.160 --> 0:20:35.840 upgrading to meat, what if one of the significant upgrades 0:20:35.920 --> 0:20:40.639 was too cooked food, allowing for easier digestion and a 0:20:40.640 --> 0:20:45.680 bigger brain. So about one point seven million years ago 0:20:45.760 --> 0:20:49.080 or so, about the time of the emergence of Homo erectus, 0:20:49.640 --> 0:20:52.480 when the modern human body plan first shows up. This 0:20:52.520 --> 0:20:55.400 is when you see human bodies that are shaped more 0:20:55.520 --> 0:20:59.520 or less like Homo sapiens are today cooking Under this 0:20:59.600 --> 0:21:03.360 hypod this is could have entered the scene, making difficult foods, 0:21:03.480 --> 0:21:06.760 tough roots and tubers and stuff available on the open 0:21:06.800 --> 0:21:10.920 savannah into a digestible, a real thing that you could 0:21:10.960 --> 0:21:13.320 digest and get good energy from as long as you 0:21:13.359 --> 0:21:17.720 could cook it. Now, I said that this hypothesis was 0:21:17.760 --> 0:21:20.320 not fully accepted everywhere, and that's the case. So from 0:21:20.359 --> 0:21:24.320 what I'm reading more research has seriously called into question 0:21:24.480 --> 0:21:29.080 many aspects of our previous understanding of the expensive tissue hypothesis. 0:21:29.080 --> 0:21:32.920 There appears to be a period of right now conflicting 0:21:33.000 --> 0:21:36.560 evidence and reinterpretation. Just doing a search for scientific articles 0:21:36.560 --> 0:21:39.040 published within the last four years or so, I found 0:21:39.040 --> 0:21:41.959 a bunch claiming to find evidence for the expensive tissue 0:21:42.040 --> 0:21:45.840 hypothesis within certain species or groups of animals, others claiming 0:21:45.920 --> 0:21:48.840 not to find any evidence within certain species or groups. So, 0:21:49.160 --> 0:21:50.760 as far as I can tell, this one is up 0:21:50.760 --> 0:21:54.360 in the air. Um And with respect to the cooking hypothesis, 0:21:54.960 --> 0:21:57.440 one important piece of evidence would be that in order 0:21:57.520 --> 0:22:02.440 to sort of track within cephalization history with the growing 0:22:02.520 --> 0:22:05.560 brains of our hominid ancestors, it would need to be 0:22:05.600 --> 0:22:09.159 supported by evidence of very early fire use in hominids. 0:22:09.200 --> 0:22:12.040 Now earlier, what did we say was the earliest known 0:22:12.080 --> 0:22:15.440 fire use. We saw those hearths, you know, four hundred thousand, 0:22:15.560 --> 0:22:18.880 seven hundred thousand years ago or so, we saw maybe 0:22:18.960 --> 0:22:21.960 evidence of burning going back earlier, maybe to one point 0:22:21.960 --> 0:22:25.399 five million years ago or something like that. But this 0:22:25.440 --> 0:22:28.480 would need to show fire use going way way back 0:22:28.680 --> 0:22:31.920 earlier than is generally accepted. But I would also say 0:22:32.040 --> 0:22:35.400 within the realm of possibility, maybe maybe you degree based 0:22:35.440 --> 0:22:37.440