5 ms·

picture two exponential growth curves, one steeper than the other, over time the a trend moves from the steeper curve to the less steep curve. The "population"

picture two exponential growth curves, one steeper than the other, over time the a trend moves from the steeper curve to the less steep curve. The "population" whatever it is, is still growing exponentially at the less steep curve.

maxerickson 9y ago
The idea is that an exponential curve is no longer the correct model for forecasting growth past 2070. Arguing about how to express that is sort of pointless.
- candiodari 9y ago
  Population growth in non-human species is quite well documented and is in fact not exponential, although the early stages look exponential. It is in fact a logistic sigmoid function. It is amazing, in that it is not what you'd expect : clearly the vast majority of species have the ability to correctly estimate the carrying capacity of a habitat and only overshoot by a little bit. So the Malthusian argument is incorrect, probably, if humans are like other animals (and since population growth curves in many localities do indeed look like S-curves I would say that this ought to be the default claim). Human population size will by itself stop just shy of the carrying capacity of the planet. Which is exactly what you'd want to happen. In all likelihood, this will happen without active measures from governments (which won't work anyway due to the global nature of the required policies), with or without popularizing contraceptives, with or without female labor participation, ... (not saying those aren't desirable, just that they aren't necessary) The alternative requires an assumption that humans are hugely different from the species that we evolved from, and since this certainly isn't true in the biological sense, why would our population growth be so very different ? Humans are not the first large animal to "conquer the planet", and reach population numbers in the billions, with some fish well on the way to trillions even today, and we aren't the biggest species in terms of total biomass by a very long way (amongst non-plants that honour likely goes to ants, but even pathetic species of bacteria dwarf their numbers). Will we be the last one ? Perhaps, but it seems unlikely. https://en.wikipedia.org/wiki/Logistic_function#In_ecology:_modeling_population_growth https://en.wikipedia.org/wiki/Logistic_function#In_ecology:_...
  - nostrademons 9y ago
    It's not that species have the ability to correctly estimate the carrying capacity of the environment. It's that when the population of a species exceeds the carrying capacity of the environment, individuals will die and/or fail to reproduce, dropping the population of the next generation. It's very likely that humans exhibit the same behavior, but on a micro-scale, this isn't very comforting. If a politician says "Well, the earth will be fine, but 10% of you are gonna die and another 30% won't be able to have children that survive to adulthood", there would be rioting on the streets ... which has a non-negligible chance of bringing about those numbers. Nature will be just fine, but remember that the mechanisms by which nature self-adapts are the four horsemen of the apocalypse: pestilence, war, famine, and death.
  - dualogy 9y ago
    > So the Malthusian argument is incorrect, probably, if humans are like other animals > The alternative requires an assumption that humans are hugely different from the species that we evolved from Well we are, for proof look at the fact that we're even discussing it here when all the other species never did. Look, that all sounds very peachy if it weren't for the fact that our species alone has grown the brains and the self-justifications for consciously attempting to continously outwit "nature" (and be able to replicate way beyond what our ancestral habitats could carry) at every turn with agriculture and all the sciences =) granted, there's no point in or way of "going back" for all manner of reasons, but we needn't lose sight of certain basic facts here..
  - ljw1001 9y ago
    I refer you to the 12,000-year human population growth chart on Our World In Data, in a post by Max Roser. https://ourworldindata.org/world-population-growth/ https://ourworldindata.org/world-population-growth/ Growth is clearly exponential. Your theories don't fit the data.
    - candiodari 9y ago
      I'm looking at that graph. I see a spike in the growth rate, after the spike it goes to zero. I'm not an expert (I have a masters in statistics actually) but that doesn't look very exponential to me. Can you explain what I'm missing ?

maxerickson 9y ago

The idea is that an exponential curve is no longer the correct model for forecasting growth past 2070. Arguing about how to express that is sort of pointless.

candiodari 9y ago
Population growth in non-human species is quite well documented and is in fact not exponential, although the early stages look exponential. It is in fact a logistic sigmoid function. It is amazing, in that it is not what you'd expect : clearly the vast majority of species have the ability to correctly estimate the carrying capacity of a habitat and only overshoot by a little bit. So the Malthusian argument is incorrect, probably, if humans are like other animals (and since population growth curves in many localities do indeed look like S-curves I would say that this ought to be the default claim). Human population size will by itself stop just shy of the carrying capacity of the planet. Which is exactly what you'd want to happen. In all likelihood, this will happen without active measures from governments (which won't work anyway due to the global nature of the required policies), with or without popularizing contraceptives, with or without female labor participation, ... (not saying those aren't desirable, just that they aren't necessary) The alternative requires an assumption that humans are hugely different from the species that we evolved from, and since this certainly isn't true in the biological sense, why would our population growth be so very different ? Humans are not the first large animal to "conquer the planet", and reach population numbers in the billions, with some fish well on the way to trillions even today, and we aren't the biggest species in terms of total biomass by a very long way (amongst non-plants that honour likely goes to ants, but even pathetic species of bacteria dwarf their numbers). Will we be the last one ? Perhaps, but it seems unlikely. https://en.wikipedia.org/wiki/Logistic_function#In_ecology:_modeling_population_growth https://en.wikipedia.org/wiki/Logistic_function#In_ecology:_...
- nostrademons 9y ago
  It's not that species have the ability to correctly estimate the carrying capacity of the environment. It's that when the population of a species exceeds the carrying capacity of the environment, individuals will die and/or fail to reproduce, dropping the population of the next generation. It's very likely that humans exhibit the same behavior, but on a micro-scale, this isn't very comforting. If a politician says "Well, the earth will be fine, but 10% of you are gonna die and another 30% won't be able to have children that survive to adulthood", there would be rioting on the streets ... which has a non-negligible chance of bringing about those numbers. Nature will be just fine, but remember that the mechanisms by which nature self-adapts are the four horsemen of the apocalypse: pestilence, war, famine, and death.
- dualogy 9y ago
  > So the Malthusian argument is incorrect, probably, if humans are like other animals > The alternative requires an assumption that humans are hugely different from the species that we evolved from Well we are, for proof look at the fact that we're even discussing it here when all the other species never did. Look, that all sounds very peachy if it weren't for the fact that our species alone has grown the brains and the self-justifications for consciously attempting to continously outwit "nature" (and be able to replicate way beyond what our ancestral habitats could carry) at every turn with agriculture and all the sciences =) granted, there's no point in or way of "going back" for all manner of reasons, but we needn't lose sight of certain basic facts here..
- ljw1001 9y ago
  I refer you to the 12,000-year human population growth chart on Our World In Data, in a post by Max Roser. https://ourworldindata.org/world-population-growth/ https://ourworldindata.org/world-population-growth/ Growth is clearly exponential. Your theories don't fit the data.
  - candiodari 9y ago
    I'm looking at that graph. I see a spike in the growth rate, after the spike it goes to zero. I'm not an expert (I have a masters in statistics actually) but that doesn't look very exponential to me. Can you explain what I'm missing ?