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How can Malthus be discredited? He said that the population tends to grow to the limit of the food supply, and then suffer periodic famine as the weather fluctu

How can Malthus be discredited? He said that the population tends to grow to the limit of the food supply, and then suffer periodic famine as the weather fluctuates. This is an obvious truth. It matters because subsistence living is probably not compatible with a high-tech society.

bryanlarsen 14y ago
No, it's obviously wrong. Population does not grow to the limit of food supply: food supply has increased dramatically in the first world over the last century, yet population growth has flatlined in most first world countries.
- Daniel_Newby 14y ago
  Ah, you are talking about a momentary decrease in the rate during a time of enormous change. In the long run, population grows to the limits of resources. Natural selection always selects for more descendants, and the population always hits the resource limits. The only alternative is for natural selection to cease operating. Incidentally, population growth has not flatlined uniformly in First World countries. There are identifiable subgroups that have very high fecundity, and whose descendants are capable of eating any possible green revolution within a few centuries at the most.
  - bryanlarsen 14y ago
    The biggest population growth in history was accompanied by a green revolution that increased food production even faster. So example indicates that you're likely wrong. We're now in an age where energy is cheap, and energy can be converted to food relatively easily. The amount of energy required to feed the entire world is now a small fraction of total world energy production. The fact that we don't do it this way is only because food is even cheaper than energy. And yes, our oil energy supplies are relatively constrained, but our alternative supplies (aka nuclear) are not. So "any possible green revolution" is pretty darn big. If we wanted to, we could feed a trillion people using nuclear power lighting artificial greenhouses.
    - Daniel_Newby 14y ago
      Populations under natural selection grow exponentially in the presence of sufficient food. If we have 100,000 times more food capacity than we need, and the population doubling time is a very slow 100 years, then we hit the Malthusian limit in 1,700 years. Exponential growth is a powerful process. This is the reason so many science fiction stories are set on a future Earth that is baking hot (industrial waste heat) and has fertility police that terminate unlicensed pregnancies. It's a simple extrapolation of current conditions.
      - ars 14y ago
        Malthus forgot something very basic: Unlike animals, Humans create their own resources, they don't just find them in the environment. So it doesn't matter how many humans you have, there will always be enough resources. Remember that from a physical point of view nothing can ever be destroyed. The only thing that happens is the atom moves from one place to another. With application of energy and brains, you can move that atom right back to where you want it.
        Daniel_Newby 14y ago
        > Unlike animals, Humans create their own resources, they don't just find them in the environment. No. There are hard limits to resources, but exponential growth curves have no upper bounds. For example, humans could disassemble all the planets in the Solar system and turn them into space stations, increasing the habitable area by a factor of a trillion trillion. For a population doubling time of 20 years, the new territory will be filled up in a few thousand years. If we convert all the solid matter in the galaxy into space stations, the galaxy will hit the Malthusian limit within a few million years. The only solution to an exponential growth curve is starvation or artificial selection.

bryanlarsen 14y ago

No, it's obviously wrong. Population does not grow to the limit of food supply: food supply has increased dramatically in the first world over the last century, yet population growth has flatlined in most first world countries.

Daniel_Newby 14y ago
Ah, you are talking about a momentary decrease in the rate during a time of enormous change. In the long run, population grows to the limits of resources. Natural selection always selects for more descendants, and the population always hits the resource limits. The only alternative is for natural selection to cease operating. Incidentally, population growth has not flatlined uniformly in First World countries. There are identifiable subgroups that have very high fecundity, and whose descendants are capable of eating any possible green revolution within a few centuries at the most.
- bryanlarsen 14y ago
  The biggest population growth in history was accompanied by a green revolution that increased food production even faster. So example indicates that you're likely wrong. We're now in an age where energy is cheap, and energy can be converted to food relatively easily. The amount of energy required to feed the entire world is now a small fraction of total world energy production. The fact that we don't do it this way is only because food is even cheaper than energy. And yes, our oil energy supplies are relatively constrained, but our alternative supplies (aka nuclear) are not. So "any possible green revolution" is pretty darn big. If we wanted to, we could feed a trillion people using nuclear power lighting artificial greenhouses.
  - Daniel_Newby 14y ago
    Populations under natural selection grow exponentially in the presence of sufficient food. If we have 100,000 times more food capacity than we need, and the population doubling time is a very slow 100 years, then we hit the Malthusian limit in 1,700 years. Exponential growth is a powerful process. This is the reason so many science fiction stories are set on a future Earth that is baking hot (industrial waste heat) and has fertility police that terminate unlicensed pregnancies. It's a simple extrapolation of current conditions.
    - ars 14y ago
      Malthus forgot something very basic: Unlike animals, Humans create their own resources, they don't just find them in the environment. So it doesn't matter how many humans you have, there will always be enough resources. Remember that from a physical point of view nothing can ever be destroyed. The only thing that happens is the atom moves from one place to another. With application of energy and brains, you can move that atom right back to where you want it.
      - Daniel_Newby 14y ago
        > Unlike animals, Humans create their own resources, they don't just find them in the environment. No. There are hard limits to resources, but exponential growth curves have no upper bounds. For example, humans could disassemble all the planets in the Solar system and turn them into space stations, increasing the habitable area by a factor of a trillion trillion. For a population doubling time of 20 years, the new territory will be filled up in a few thousand years. If we convert all the solid matter in the galaxy into space stations, the galaxy will hit the Malthusian limit within a few million years. The only solution to an exponential growth curve is starvation or artificial selection.