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Thomas Malthus and population growth

Thomas Malthus's views on population. Malthusian limits. Created by Sal Khan.

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  • male robot hal style avatar for user keatonfreeman15
    It seems like we have more junk food today and less real food than people did in the past. Is this the case?
    (28 votes)
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  • leaf red style avatar for user Andrew Breitweiser
    If there is a "Malthusian limit", what would be the impact of longer life spans on this limit?
    (17 votes)
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    • starky sapling style avatar for user QTPyah
      Population is affected by the death of and birth of our human species. A longer lifespan would cause a greater increase in population because the older generation would not die so early. They would stay alive with their Children and maybe even Great Great Grandchildren, possibly even reproducing for a longer time period because of their longevity. This would add to the collective population on a whole. The Malthusian limit would be reached faster because all of these people do need to eat at their no doubt HUGE family reunions and this is where crops come into affect.
      (3 votes)
  • leaf grey style avatar for user cmaryk12296
    But due to medical advancements the human life-span has increased, therefore if people live a very long time, and younger generations still reproduce, will there be enough food production crops, live stock, factory,etc and land for everyone?
    (8 votes)
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  • marcimus pink style avatar for user AT
    I think T.M is right to a certain extent. We do tend to reproduce more when there's food and better living conditions but the demographic transition prevents us from reaching the "Malthusian line"

    There's a possible chance that the Malthusian law might occur (to some resources) due to the mass consumption society which we live in and which overpopulated nations like China ans India will sooner or later transform into. But this creates a new law called the Recourse limitation by over consumption
    (7 votes)
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    • blobby green style avatar for user Avram Primack
      This statement has several flaws....if the demographic transition keeps us from reaching the line then why hasnt it happened in Africa? The Malthusian catastrophe does not happen to resources, it happens to people. People exceed the natural limitations, or the natural limitations change and population adjusts. I dont know what is intended by resourse limitation by over consumption, or why it would be a new law when no new law is needed....
      (1 vote)
  • piceratops ultimate style avatar for user Meir
    why does Sal draw the population line straight even though the birth rate is usually around a certain amount of the overall population?
    (2 votes)
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  • blobby green style avatar for user Tom Lott
    TM was, of course, ahead of birth control and the sexual revolution, which de-railed the principles in "The Population Bomb" by Paul Ehrlich in the early 1970's. These factors result in lower than the 2.2 babies per family to increase a country's population in developed countries. I wonder what the effect of Catholic and Mormon(and other cultural) birth rates are on developed countries?
    (3 votes)
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    • male robot hal style avatar for user Master Mom
      Research you population demographics. Most industrialized countries are in a demographic winter for native born citizens - immigration brings them to population replacement levels. However, the largest demographic surplus is coming from the Middle East. Even Mormons and Catholics are having smaller families compared to the Muslim nations (I should know I've been a Mormon my whole life). Check out the demographic decline over the next 50 years for China and the rest of Asia - the pyramid will be turned upside down with far more elderly than youth. If you look you can find minutes to meetings concerning their worry over how the young will fill enough jobs to support the elderly.
      (1 vote)
  • starky sapling style avatar for user Dawson
    Won't human population eventually get so big that earth wouldn't be able to handle it?
    (1 vote)
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  • orange juice squid orange style avatar for user Emma™
    if there are enough calories and food and money and stuff like that then why is there such a staggering ammout of poor people in the us?
    (1 vote)
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  • blobby green style avatar for user annroshermione
    Does negative population growth mean that the particular country having the negative population(japan,germany) growth is stable??
    (0 votes)
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  • primosaur ultimate style avatar for user alexrocksserra
    Have Germany and Japan already hit the Malthusian limit?
    (1 vote)
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    • blobby green style avatar for user Etcyl
      No. In fact, just as he indicated toward the end of this film, most post-modern countries (e.g. Japan, the U.S., Germany et. al.) experience a population decline rather than a population increase. In other words, something natural - not cited by Malthus, coincidentally - causes post-modern countries, for example Japan, to have a lower population as time continues past modernity. It is said that the United States would exhibit this as much as most European nations if it were not for the influx of immigrants.
      (3 votes)

Video transcript

The 1700s in Europe are often referred to as the Age of Enlightenment. It was a time, we'd come out of the Renaissance. We'd rediscovered science and reason and in the 1700s, we saw that come about with even more progress of society. As we exit the 1700s and enter into the 1800s, we start having the Industrial Revolution. And people saw the steady march of human reason, of human progress. And because of this, a lot of people were saying, hey, humanity will continue to improve. It will improve forever, to a point that poverty will go away. We will turn into this perfect utopian civilization without wars, without strife of any kind. And there was something to be said about that. You had significant improvements. In fact, you had even more dramatic improvements once the Industrial Revolution started. But not every one in the late 1700s was as optimistic. And one of the more famous not-so-optimistic people was Thomas Malthus, right over here. And I will just quote him directly. This is from his "Essay on the Principle of Population." "The power of population is so superior to the power of the earth to produce subsistence for man, that premature death must, in some shape or other, visit the human race." Very uplifting. "The vices of mankind are active and able ministers of depopulation. They are the precursors in the great army of destruction, and often finish the dreadful work themselves. But should they fail in this war of extermination, sickly seasons, epidemics, pestilence, and plague advance in terrific array, and sweep off their thousands and tens of thousands. Should success still be incomplete, gigantic, inevitable famine stalks in the rear, and with one mighty blow levels the population with the food of the world." So not so uplifting of a little quote right over here. But this was his general sense. He lived in a time where people were being very optimistic that progress, the march of progress, would go on forever until we got to some utopian civilization. But from Thomas Malthus' point of view, he felt that if people could reproduce and increase the population, they will, that there's no way of stopping them. So from his point of view, the way he saw it-- so let me on that axis-- let's say that that is the population, and that this axis right over here, let's say that that is time. So by his thinking-- and everything that he'd seen in reality up to that point would back this up-- that if people had enough food and time, they would reproduce, and they would reproduce in numbers that would grow the population. So in his mind, the population would just keep on increasing. It'll just keep on increasing, until it can't support itself anymore, until the actual productivity of the land can't produce enough calories to feed all of those people. So in his mind, there would be some natural upper bound based on the actual amount of food that the earth could support. So let's say that this is-- let me do that in a different color-- so in his mind, there was some upper bound, and once you get to that upper bound, then all of a sudden, the vices of mankind will show up. And if those don't start killing people, then all of these other things will, epidemics, pestilence, plague, and then famine. People are actually starving to death. So in his mind, once you got to this level, maybe you had a couple of good crops, people are feeling good about themselves, they overpopulate. But then, all of a sudden, you have a bad crop, or because you have a bad crop, people start fighting over resources, and wars happen. Or maybe the population is so dense that a plague develops. And then you have a massive wave of depopulation. And so you would just oscillate around this limit. And this limit some people refer to as a Malthusian limit, but it's just really the limit at which the population can sustain itself. And from Thomas Malthus' point of view, he did recognize that there were technological improvements, especially in things like agriculture. And that this line was moving up. He had seen it in his own lifetime, that this line had moved up. But from his point of view, however far you moved this line up, the population will always compensate for it and catch up to it, and eventually get to these Malthusian limit. And then the same not-so-positive things that he talks about would actually happen. And some people now say, oh Thomas Malthus, he was so pessimistic. He was obviously wrong. Look at what's happened. We have so much food on this planet right now. We've gone through multiple agricultural revolutions, and they are right. In the last 200 years, since Malthus, so since the early 1800s, we really have been able to outstrip population. So this line up here has been moving up much faster than even population. So right now, we actually do have more calories per person on the planet than we've had at any time in history. But it's not saying that Thomas Malthus was wrong, it's just saying that maybe he was just a little bit pessimistic in when that limit will be reached. Now the other dimension where you might say that he was maybe wrong was in this principle that a population will increase if it can increase. If there is food, and if there is time, people will reproduce. And a good counterpoint to that is what we've now observed in modern, developed nations. And so this right over here shows the population growth. I got this from the World Bank. But the population growth of some modern, developed nations. And you can see the United States is pretty low, but it's still positive. It's still over half a percent. But even that adds up when you compound it. But if you look over here, Japan and Germany-- and Japan and Germany have less immigration than the United States, especially Japan-- they are actually negative. So just this population left to its own devices, especially if you account for people not going across borders, just the population itself growing, they actually have negative growth. So there's some reason to believe that this is evidence that Thomas Malthus was wrong, or not completely right. He didn't put into account that maybe once a society becomes rich enough and educated enough, that they might not just populate the world, or have as many kids as they want, they might try to do other things with their time, whatever that might be. So I just wanted to expose you to this idea. Time will tell if Thomas Malthus, if we can always keep this line of food productivity growing faster than the population. And time will tell whether our populations can become, I guess we could say, developed enough, so that they don't inex-- I can never say that word. They don't always just keep growing. Maybe they do become a Japan or a Germany situation. And the world population, especially if we have a high rate of literacy, eventually does level off. So it never even has a chance of hitting up against that Malthusian limit. But I thought I would introduce you to the idea, and now you can go to parties and you can talk about things like Malthusian limits. And if you want to know what country is maybe closest to the Malthusian limit right now-- and we've talked about this before-- but a good case example is something like Bangladesh. They are, right now, the most population-dense country in the world. They have 900 people per square kilometer. And just to give you a sense of perspective, that's 30 times more dense than the United States is. So if you took every person in the United States, and turned them into 30 people in the United States, that would give you a sense of how dense Bangladesh is. And it's probably due to a certain degree that it's a very fertile land. The river delta of the Ganges essentially makes up the entire country. But they do, they have in the past, had famines. They've gotten a little bit beyond that. But still, you do have major problems with flooding and resources. So hopefully they'll be able to stay ahead of the curve.