Thursday, October 19, 2006

Review of David Stove: Darwinian Fairytales (essay 3)

As Stove announced in Essay II, he will in Essay III, "But What About War, Pestilence, and All That?" deal with the objections against his claim that Darwin considered limited food supplies the ultimate check on population size. He gives some quotes to support that.

The essay is headed by this quote from The Descent of Man, chapter 2:

The primary or fundamental check to the continued increase of man is the difficulty of gaining subsistence, and of living in comfort. We may infer that this is the case from what we see, for instance, in the United States, where subsistence is easy, and there is plenty of room. If such means were doubled in Great Britain, our number would be quickly doubled. [emphasis by Stove]

The following discussion revolved around this quote.

Stove comes up with many other factors that could limit human population growth, such as on p. 34:

There are first the qualifications which Malthus and Darwin themselves made to it, (and then effectively ignored). That is, 'population increases if food does, unless it is prevented from doing so by disease, or by war, or by emigration, or by homosexuality, or by contraception, abortion, or infanticide'. But then, there are many other qualifications which are equally necessary, even though most of them were completely undreamt-of by either Malthus or Darwin. For example, '... unless there are widespread massacres, persecutions, or deportations'. Then, '... unless there is a mass revival of sexual asceticism'. Again, '... unless a suicide cult sweeps through the population'. Yet again, '... unless an environmentalist panic about "overpopulation" sweeps through the population'. Then '... unless there is an epidemic of feminist motherhood-phobia'.

Yes, this is all true; but how about long-term? In former times in Japan, the unit of currency was koku, the amount of rice needed to feed one man for a year. From the point of view of a daimyo this was practical, because it made it easy to calculate the minimum number of peasants needed to support both themselves and the maximum possible number of soldiers to allow the daimyo to increase his area and thereby his possible koku count. The ultimate check is food. Far the most of the worlds domesticated animals and cultivated plants are for food, not pets or decoratives. Also many animals that are not eaten have importance in food supply, such as sheep-dogs and horses - the latter, of course, mostly in former times. Now, of course, how much food can be produced from a certain peace of land depends on technology and social organization, and it's rather the latter that limits population size; how many workers are needed? Increasing the number of workers does not itself increase output. You cannot sow and harvest twice on a field just because you double the number of workers. So, food does play an important role, though things are more intricate than mere food.

Stove mentions that what is so special with food is that it is a non-shareable advantage; you cannot eat the food that I eat and vice versa. As he also mentions, this goes for air as well, but this far, air hasn't been a scarce resource; that is, we do not have to work to produce air and therefore there is no labor arganization needed, unlike with food. Stove doesn't mention this; but it's actually a key factor.

On p. 36, Stove gives examples of shareable advantages. The first one is

immunity to a certain disease. If organism A has this immunity, while some of its local conspecifics do not, this fact will certainly give A an advantage (if other things are equal) in the struggle for life. Yet A's having this immunity does nothing to prevent B's also having it. It is not as though there is only a limited fund of the immunity to be shared out among the members os a species, so that more of it means less for another.

The second is "improved defence against predators" - such as sharper hearing, which follows the same rule as above.

These are odd examples in that food isn't a question of genes (except in the sense that organisms with different genes may have different food preferences), whereas immunity to diseases and shaper hearing or sight is. Now, an organism with immunity to a disease that's running wild will survive and pass on its genes to its offspring, whereas the organism without the immunity will die and so will its offspring. That's how the immunity is made a shared advantage. A genetic advantage isn't simply shareable right away; we don't - yet - copy genes from each other just as we see fit.

Denyse O'Lery's review of Essay III can be found here.

O'Leary runs along with the idea that Darwin (and Malthus) considered food to be the only real limit to population size, and that this is not necessarily the case, not even for animals. Concerning this last, she writes:

It is not clear that food supply is always the central factor in all animal populations either. One thinks, for example, of wolf packs, where the jealousy of the alpha male may well prevent his subordinates from mating, even if food is plentiful.

Yes, food is plentiful this summer; but how are we going to feed the extra cubs during winter time? Some species do indeed react to plentiful food by increasing in number and then taking a severe punishment, when the days of plenty are over; but other species are slower to react to that kind of things, which also spares them for the punishment. But the latter doesn't mean that a wolf pack isn't as big as it can be when averaging over a few years.

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