Malthus on population

While travelling to, round and back from England lately I read An essay on the principle of population, by Thomas Robert Malthus (1766–1834). This essay famously helped Darwin solve part of the riddle of evolution.

Malthus' basic argument is that population tends to grow exponentially (that is, the birth-rate is proportional to the population) unless held in check; but that the available supply of food to feed the population cannot grow comparably. Consequently, if nothing else holds population in check, famine shall.

Malthus pursues the matter in rather more detail than this brief synopsis. He makes a reasonable argument that it would be a remarkable achievement even to grow food production by as much, each twenty-five years, as the total production at the time Malthus wrote his first draft of the essay. He concedes that one might pull off this feat in the first twenty-five years; but contends that repeating the feat in the next twenty-five would be astonishing; and, beyond that, quite incredible. None the less, even if such increase were possible, it could not keep up with population growth.

It would, in fact, be interesting to see how global food production has grown over the intervening two centuries (and a bit). We have made vast improvements in the productivity of land, sufficient to sustain a major growth in the total population of the world in that time. Folk have tended to ignore Malthus as a result: we have increased food production faster than he would have credited. He anticipated the importation of food from other lands, which contributes to the ability of the world's rich nations to grow their populations – at the expense of the poorer nations. He anticipated increase in the proportion of land given over to agricultural production, though he only assessed it for Britain, where there was little room for expansion: but we have significantly expanded the growth of agricultural use of land in the rest of the world (generally at the expense of forest land and other habitats crucial to the survival of other species). We have added significant technological improvements, among which I would include the development of more productive strains of various crops. It remains that Malthus' central argument still holds true: whatever short-term gains we may make, there is ultimately a limit to the amount of food the planet can produce. Because food production thus cannot (indefinitely) grow exponentially, population growth must ultimately be checked by famine, if it is not first checked by other means.

Malthus also explores the other ways population may be held in check. He characterizes these as vices and causes of misery and distress; and he divides them into preventive and positive types. Those social and economic factors which discourage marriage, and especially early marriage, serve as preventive checks to population growth, by reducing the birth-rate. [Here, we must interpret marriage as when a couple embark on having children: since Malthus' day, Western culture has adjusted its cultural forms enough that many couples marry without intent to have children; and many have children without marriage.] He points out that such restraint is facilitated by prostitution, which (along with contraception) he classifies as vice; and that, without vice, the implied self-restraint is a cause of misery. The positive checks are plague, famine, war and the like – among which, Malthus portrays famine as the final and most decisive. These he naturally characterizes as causes of misery and distress.

Malthus takes it as a given that, once married, a couple shall produce (pretty much) as many children as is biologically possible: thankfully, we have since found that cultural changes can reduce that. Women, given even moderate education, are not so keen to be baby factories. Indeed, one's offspring shall fare better if one has only a few and devotes as much effort to their raising as to the raising of more, thus giving more effort to each. The wide-spread cultural acceptance of contraception has – in the cultures which have accepted it – made it possible for couples to limit their productivity of children despite giving in to the natural urges which Malthus felt sure were guaranteed to maintain a high birth rate.

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