1 00:00:00,000 --> 00:00:04,033 For us modern humans with our easy access to the local supermarket 2 00:00:04,033 --> 00:00:07,974 it's easy to forget that throughout human history and even today 3 00:00:07,974 --> 00:00:13,553 the amount of humans or human population has been limited by our ability to get calories 4 00:00:13,553 --> 00:00:19,144 or get human consumable food from the land, so what I want to do in this video is give us a little bit of 5 00:00:19,144 --> 00:00:22,729 a framework for thinking about how humans have been gathering 6 00:00:22,729 --> 00:00:28,102 calories from the land and how that's placed an upper limit on the number of humans 7 00:00:28,102 --> 00:00:32,698 that can live in any given area, or the population density of humans. 8 00:00:32,698 --> 00:00:38,890 So right over here you have some gentlemen looking for food, they are hunter-gatherers. 9 00:00:38,890 --> 00:00:45,808 I'll say HG for short, and the H part, the hunter part that they might actually find some animals. 10 00:00:45,808 --> 00:00:48,472 I think these guys are trying right over here are trying to trap some rabbits 11 00:00:48,472 --> 00:00:51,371 and the gathering part, they're just literally looking for food 12 00:00:51,371 --> 00:00:59,804 maybe they find fruit of some sort, or some nuts or maybe some roots that are edible by humans 13 00:00:59,804 --> 00:01:04,369 so literally just walk around either try to kill things or find things they can consume. 14 00:01:04,369 --> 00:01:08,223 So I'll call this right over here stage one. 15 00:01:08,223 --> 00:01:12,392 So this is hunter-gatherers, this is what most humans 16 00:01:12,392 --> 00:01:15,974 have done through most of human history. 17 00:01:15,974 --> 00:01:18,221 And just to give us a little bit of a framework 18 00:01:18,221 --> 00:01:20,301 for how much they could get from the land, 19 00:01:20,301 --> 00:01:25,062 I looked in some of the best sense of studying HG populations 20 00:01:25,062 --> 00:01:29,109 in land like this maybe they can get about 200 calories. 21 00:01:29,109 --> 00:01:35,895 I'll make this a whole column, this whole column is the amount 22 00:01:35,895 --> 00:01:42,722 that they can get in terms of calories per square kilometre per day. 23 00:01:42,722 --> 00:01:44,968 Now it's obviously going to be hugely dependent 24 00:01:44,968 --> 00:01:47,226 on the number of animals that live there, 25 00:01:47,226 --> 00:01:50,642 the type of land that's there, if they're next to a stream 26 00:01:50,642 --> 00:01:52,809 where maybe fish are just jumping out of the stream 27 00:01:52,809 --> 00:01:54,435 this number would be much higher, 28 00:01:54,435 --> 00:01:55,727 if they were in some type of desert 29 00:01:55,727 --> 00:01:57,217 this number would be much lower. 30 00:01:57,217 --> 00:01:59,227 But this is actually fairly in line with 31 00:01:59,227 --> 00:02:01,710 some of the studies of HG cultures. 32 00:02:01,710 --> 00:02:05,226 Now if this the number of calories that they can get 33 00:02:05,226 --> 00:02:06,810 from each square kilometre per day, 34 00:02:06,810 --> 00:02:09,306 how many humans can live in a square kilometre per day? 35 00:02:09,306 --> 00:02:10,975 What is the density of humans? 36 00:02:10,975 --> 00:02:13,813 Well, to firgue that out we have know on average 37 00:02:13,813 --> 00:02:17,227 how many calories does a human need to survive, 38 00:02:17,227 --> 00:02:19,801 and for the sake of this video I'm going to make the assumption 39 00:02:19,801 --> 00:02:26,557 that a human being needs 2,000 calories per day 40 00:02:26,557 --> 00:02:29,642 to survive in a non-malnourished state. 41 00:02:29,642 --> 00:02:31,722 And obviously it's hugely dependent on 42 00:02:31,722 --> 00:02:35,055 how activ this person is or how large they are. 43 00:02:35,055 --> 00:02:37,550 And one other note: this whole I will be using 44 00:02:37,550 --> 00:02:39,477 Calories with the capital C. 45 00:02:39,477 --> 00:02:42,218 The Calories with the capital C are the calories 46 00:02:42,218 --> 00:02:44,638 that people are used to refering to when you go to the gym 47 00:02:44,638 --> 00:02:47,052 and you run on the treadmill and it says how many calories you've burnt 48 00:02:47,052 --> 00:02:50,074 or you look at the back of your candy bar and it says 200 calories. 49 00:02:50,074 --> 00:02:52,440 These are tha calories I'm talking about. 50 00:02:52,440 --> 00:02:55,526 They're slightly different notion than the calories 51 00:02:55,526 --> 00:02:56,969 that you encounter in your chemistry class. 52 00:02:56,969 --> 00:03:01,728 Those calories are calories with a lower case c. 53 00:03:01,728 --> 00:03:05,729 And just so that you can be optimally confused it turns out that 54 00:03:05,729 --> 00:03:16,453 1 Calory with an upper case C is equal to 1,000 calories with a lower case c. 55 00:03:16,453 --> 00:03:20,556 And the lower case c calories are the amount of energy 56 00:03:20,556 --> 00:03:25,136 needed to heat 1 gramme of water 1°C. 57 00:03:25,136 --> 00:03:27,057 So this is what you see in your chemistry class 58 00:03:27,057 --> 00:03:29,969 but this is not what we are going to be talking about in this video. 59 00:03:29,969 --> 00:03:32,141 We're talking about the capital C Calories 60 00:03:32,141 --> 00:03:35,143 that dietitians are always talking about. 61 00:03:35,143 --> 00:03:39,144 So with this assumption that the average human eats 2000 Calories a day 62 00:03:39,144 --> 00:03:41,971 to not get malnourished, and obviously man would eat more, 63 00:03:41,971 --> 00:03:45,137 women would eat less, children would eat even less, 64 00:03:45,137 --> 00:03:48,097 but with this assumption, what is the density of humans 65 00:03:48,097 --> 00:03:50,807 that could be supported by this culture right over here? 66 00:03:50,807 --> 00:03:56,804 Well, 200 Calories is 1 tenth of the average daily human requirement 67 00:03:56,804 --> 00:03:58,387 if you believe this assumption. 68 00:03:58,387 --> 00:04:05,305 The the population density, humans per square kilometre 69 00:04:05,305 --> 00:04:10,303 you can always support 1 tenth of a human with this Calory output! 70 00:04:10,303 --> 00:04:15,311 So you can only support 0.1 of a human per a square kilometre. 71 00:04:15,311 --> 00:04:18,308 So 1 human would actually need 10 square kilometres 72 00:04:18,308 --> 00:04:23,394 to hunt from and gather from in order to support just themselves! 73 00:04:23,394 --> 00:04:26,058 They would need maybe 30 or 40 square kilometres 74 00:04:26,058 --> 00:04:28,476 to support an entire family, 75 00:04:28,476 --> 00:04:30,562 so they could wander around and kill the animals 76 00:04:30,562 --> 00:04:33,559 and find whatever they need to find on that land. 77 00:04:33,559 --> 00:04:36,309 Now let's go to kind of you can view as maybe the next stage 78 00:04:36,309 --> 00:04:38,894 although it's now always the case that herding is going to be 79 00:04:38,894 --> 00:04:41,392 more productive than HG, especially with that case 80 00:04:41,392 --> 00:04:42,811 with the fish jumping out of the water, 81 00:04:42,811 --> 00:04:45,309 but let's go to the scenario right over here. 82 00:04:45,309 --> 00:04:51,149 So this is, we can call this a pastoral life-style. 83 00:04:51,149 --> 00:04:54,136 So this is 2, I'll call it pastoral. 84 00:04:54,136 --> 00:04:55,976 And over here is the realisation that, 85 00:04:55,976 --> 00:05:00,471 look, you have all of this vegetation that maybe humans can't consume 86 00:05:00,471 --> 00:05:03,724 but there are other animals that can consume this vegetation 87 00:05:03,724 --> 00:05:10,372 and they can turn those calories into calories that can be consumed by humans 88 00:05:10,372 --> 00:05:13,141 and, namely, the calories are themselves! 89 00:05:13,141 --> 00:05:14,770 So this gentleman right over here 90 00:05:14,770 --> 00:05:18,081 after he gets these sheep to be nice and fat, 91 00:05:18,081 --> 00:05:21,310 he can either eat the sheep or he can drink their milk, 92 00:05:21,310 --> 00:05:27,098 so one way to think about this cattle or these sheep right over here 93 00:05:27,098 --> 00:05:29,556 by herding them and letting them eat this grass 94 00:05:29,556 --> 00:05:36,100 he is turning non-human-consumable calories into human-consumable calories. 95 00:05:36,100 --> 00:05:38,723 And for the sake of our thought experiment let's tell we got 96 00:05:38,723 --> 00:05:44,470 10 time increase in the human-consumable calories per square kilometre. 97 00:05:44,470 --> 00:05:48,309 So now instead of 200 we're up to 2,000. 98 00:05:48,309 --> 00:05:56,558 And so instead of one human per square kilometre per day to support one human ... 99 00:05:56,558 --> 00:05:59,895 oh sorry, instead of 0.1 we can now support 1 human. 100 00:05:59,895 --> 00:06:02,808 So in that 10 square kilometres we can now support 10 people, 101 00:06:02,808 --> 00:06:06,366 in 100 square kilometres we can now support 100 people. 102 00:06:06,366 --> 00:06:09,224 Now the next stage - and I'm skipping a bunch of stages 103 00:06:09,224 --> 00:06:12,060 because we have things like subsistence agriculture 104 00:06:12,060 --> 00:06:15,474 and various forms that are not going to be equally productive, 105 00:06:15,474 --> 00:06:18,628 it depends what the land is like, it depends what tools at disposal, 106 00:06:18,628 --> 00:06:21,561 but the next stage that I'll just kind of jump to 107 00:06:21,561 --> 00:06:24,769 we can call traditional agriculture. 108 00:06:24,769 --> 00:06:29,298 So this right over here, let's call that traditional agriculture. 109 00:06:29,298 --> 00:06:34,031 And that's this one over here as well, so both of these I'm going to call traditional agriculture. 110 00:06:34,031 --> 00:06:36,975 For the purposes of this video the difference between 111 00:06:36,975 --> 00:06:39,069 traditional agriculture and modern agriculture - 112 00:06:39,069 --> 00:06:42,560 in traditional agriculture you didn't have mechanisation, 113 00:06:42,560 --> 00:06:45,562 so you had very primitive mechanisation, 114 00:06:45,562 --> 00:06:48,474 you definitely didn't have fossil fuel based engines, 115 00:06:48,474 --> 00:06:50,638 you didn't have modern pesticides, 116 00:06:50,638 --> 00:06:54,823 you didn't have modern genetically engineered crops, 117 00:06:54,823 --> 00:06:58,226 but you have some of the basic science of breeding crop 118 00:06:58,226 --> 00:07:01,228 and irrigating and using animals as tools. 119 00:07:01,228 --> 00:07:04,805 So in this stage right over here, and once again, 120 00:07:04,805 --> 00:07:07,637 it completely depends on where you are on the planet, 121 00:07:07,637 --> 00:07:10,807 how fertile the land is, how good your tools are, 122 00:07:10,807 --> 00:07:12,561 what crops you are actually producing. 123 00:07:12,561 --> 00:07:16,228 Let's assume that we've got a hundredfold increasse in the productivity. 124 00:07:16,228 --> 00:07:19,366 And looking in some of the historical records it looks like, it's depending on 125 00:07:19,366 --> 00:07:22,479 once again where you are, that's not out of the realm of possibility. 126 00:07:22,479 --> 00:07:28,229 So you have a hundredfold increase, so insdead of 2,000 calories per square kilometre per day 127 00:07:28,229 --> 00:07:33,310 you can get 200,000 calories per square kilometre per day, 128 00:07:33,310 --> 00:07:38,469 and now you can support 100 humans per square kilometre - if you wanna to! 129 00:07:38,469 --> 00:07:41,035 So you might not have 100 humans, 130 00:07:41,035 --> 00:07:44,142 one on all of the land, you might not be able to farm from, 131 00:07:44,142 --> 00:07:50,057 or there are other limits on the population for whatever they might be, 132 00:07:50,057 --> 00:07:53,226 but the important thing is to think about this upper bound. 133 00:07:53,226 --> 00:07:57,219 In this traditional you are able to get type of productivity from your land 134 00:07:57,219 --> 00:08:01,774 and you are able to in theory support 100 people per 1 square kilometre, 135 00:08:01,774 --> 00:08:04,768 that means if all of a sudden you have 200 people living there, 136 00:08:04,768 --> 00:08:06,765 they maybe every once migrate to this land 137 00:08:06,765 --> 00:08:08,432 because it seems as specially fertile 138 00:08:08,432 --> 00:08:10,055 or there are really small farmers living there, 139 00:08:10,055 --> 00:08:13,142 then all of a sudden not everyone is going to get 2,000 calories a day, 140 00:08:13,142 --> 00:08:16,770 some people might get malnourished, other people might actually starve. 141 00:08:16,770 --> 00:08:20,699 There is this upper bound on the actual number of people that can be there 142 00:08:20,699 --> 00:08:24,642 based on how productive the land actually is. 143 00:08:24,642 --> 00:08:27,224 Now let's move over to modern agriculture 144 00:08:27,224 --> 00:08:32,397 and we want to talk a little bit about what exactly is modern agriculture. 145 00:08:32,397 --> 00:08:36,475 You have machines like this combine over here 146 00:08:36,475 --> 00:08:38,432 that does a lot of the human labour. 147 00:08:38,432 --> 00:08:42,708 One human can... I'll talk about the different dimensions 148 00:08:42,708 --> 00:08:44,433 because there are actually two dimensions here: 149 00:08:44,433 --> 00:08:47,057 how much calories can you get from the land, 150 00:08:47,057 --> 00:08:53,058 and how much energy and labour can one human input into the land 151 00:08:53,058 --> 00:08:55,054 using tools at their disposal. 152 00:08:55,054 --> 00:08:57,891 So in this case cattle, these oxen pulling this plough, 153 00:08:57,891 --> 00:09:00,978 or in this case this combine that's fueled by fossil fuels. 154 00:09:00,978 --> 00:09:04,560 But in modern agriculture, because all of the things, 155 00:09:04,560 --> 00:09:07,558 you have these amazing tools, you have genetically engineered crops, 156 00:09:07,558 --> 00:09:11,724 you have modern pesticides and ... not everyone is a fan of all of these things, 157 00:09:11,724 --> 00:09:15,102 but they have hugely increased our productivity. 158 00:09:15,102 --> 00:09:18,363 So you have modern agriculture. 159 00:09:18,363 --> 00:09:21,563 Let's say that you have another factor of 10 from traditional agriculture. 160 00:09:21,563 --> 00:09:26,561 so now you can get 2,000,000 calories per square kilometre per day, 161 00:09:26,561 --> 00:09:34,149 or you can support 1,000 humans per square kilometre. 162 00:09:34,149 --> 00:09:38,725 So once again this right over here is an upper bound. 163 00:09:38,725 --> 00:09:43,305 And just to give a sense, I picked these numbers just so that nubmers would be clear 164 00:09:43,305 --> 00:09:46,142 I looked in some historical records, these are completely out of line 165 00:09:46,142 --> 00:09:49,056 with what it looks like human have been able to do in the past, 166 00:09:49,056 --> 00:09:53,230 but to give you a sense of what human populatin densities look like right now 167 00:09:53,230 --> 00:09:57,891 and why this upper bound seems to be right about correct, 168 00:09:57,891 --> 00:10:07,684 in a place like the U.S. the population density is 30 people per square kilometre, 169 00:10:07,684 --> 00:10:11,895 in a more dense country or a significantly more dense country like India 170 00:10:11,895 --> 00:10:17,561 the population density is 300 humans per square kilometre. 171 00:10:17,561 --> 00:10:21,048 And in the most population dense country in the world, 172 00:10:21,048 --> 00:10:25,040 which is where I come from, or actually I was born in New Orleans, 173 00:10:25,040 --> 00:10:27,730 but where some of my ancestors came from, 174 00:10:27,730 --> 00:10:32,725 which is Bangladesh, so there's a lot of people like me, I guess, 175 00:10:32,725 --> 00:10:41,398 Bangladesh has population density of 900 humans per square kilometre! 176 00:10:41,398 --> 00:10:44,816 To some degree this is a testament to the fertility of the land and whatever else, 177 00:10:44,816 --> 00:10:48,772 but this is pretty near the limits depending on 178 00:10:48,772 --> 00:10:51,768 agricultural productivity in what now on the land 179 00:10:51,768 --> 00:10:55,142 of modern technology, so it really makes you think 180 00:10:55,142 --> 00:10:56,638 if you don't get population under control, 181 00:10:56,638 --> 00:11:01,558 you might end up with some of these kind of hitting the wall type of scenarios. 182 00:11:01,558 --> 00:11:04,308 And so the last thing I want you to think about 183 00:11:04,308 --> 00:11:06,477 and this is why I reffered to a little bit more, 184 00:11:06,477 --> 00:11:09,481 is just think about those two dimensions 185 00:11:09,481 --> 00:11:11,640 because sometimes it get a little bit muddled. 186 00:11:11,640 --> 00:11:17,434 One is the kind of the productivity of land 187 00:11:17,434 --> 00:11:23,398 and at the other there is productivity of labour. 188 00:11:23,398 --> 00:11:28,895 So right over here in HG, they're not getting many calories from their land 189 00:11:28,895 --> 00:11:31,709 so they're right over there, and the humans have to do all the labour, 190 00:11:31,709 --> 00:11:34,130 they don't have animals helping them in any way, 191 00:11:34,130 --> 00:11:37,961 they definitely don't have robots or any types of engines helping them in any way, 192 00:11:37,961 --> 00:11:42,981 and so there have to spend a lot of human time and a lot of human labour 193 00:11:42,981 --> 00:11:45,807 doing the work, getting that productivity from the land. 194 00:11:45,807 --> 00:11:50,150 But as progress with things that aid humans, 195 00:11:50,150 --> 00:11:54,645 so for example if you all of a sudden have cattle helping you 196 00:11:54,645 --> 00:11:57,227 or you have other tools that help you, 197 00:11:57,227 --> 00:12:01,147 you get more human productivity, so less and less of human labour 198 00:12:01,147 --> 00:12:03,431 has to be used to get that productivity from the land 199 00:12:03,431 --> 00:12:05,814 so maybe other humans can do other things 200 00:12:05,814 --> 00:12:08,313 like paint pictures or become blacksmiths or whatever, 201 00:12:08,313 --> 00:12:13,145 and in this direction you get higher productivity per unit of land 202 00:12:13,145 --> 00:12:17,707 and so that comes from moving from HG to a pastoral life-style 203 00:12:17,707 --> 00:12:20,898 to traditional farming with irrigation, to modern farming. 204 00:12:20,898 --> 00:12:26,816 And so in this graph kind of tools for the individuals move us up, 205 00:12:26,816 --> 00:12:28,975 getting productivity from the land moves us right, 206 00:12:28,975 --> 00:12:32,226 modern argriculture gets us right over here. 207 00:12:32,226 --> 00:12:36,140 So we're getting mach more calories per unit land 208 00:12:36,140 --> 00:12:40,231 and we're getting much more calories per unit labour. 209 00:12:40,231 --> 00:12:44,223 So you need much smaller percentage of the human population 210 00:12:44,223 --> 00:12:47,226 actually involved in the farming. 211 00:12:47,226 --> 00:12:50,726 Anyway, I let you go there, hopefuly that gives you at least an undesrtanding 212 00:12:50,726 --> 00:12:53,891 of that food doesn't just come from nowhere, 213 00:12:53,891 --> 00:12:57,891 it really is a rate-limiting factor on humanity's population.