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A Malthusian catastrophe, sometimes known as a Malthusian check, is a return to subsistence level conditions as
a result of agricultural (or, in later formulations, economic) production being eventually
outstripped by growth in population. Theories of Malthusian catastrophe are
very similar to the subsistence theory of
wages. The main difference is that the Malthusian theories predict over several generations or centuries whereas the
subsistence theory of wages predicts over years and decades.
Traditional views
In 1761 Robert Wallace published Various Prospects of Mankind. In the tract he argued that progress would
eventually undo itself by overstocking the world with people. Thirty-seven years later, Thomas Malthus published his now famous Essay on the Principle of Population. In it, he predicted
that population growth would eventually outrun food supply. This prediction was based on the idea that population, if unchecked,
increases at a geometric rate, whereas the food supply could
only grow at an arithmetic rate. Mathematically, any increasing geometric sequence (e.g. 1, 3, 9, 27, 81) will eventually
overtake all arithmetic sequences (e.g. 10, 20, 30, 40, 50). The resulting decrease in food per person will eventually lead to
subsistence level conditions. According to Malthus, the Catastrophe can only be prevented by self-restraint or vice—which
for him included contraception, abortion and homosexuality.
Malthus did not give a time frame for his catastrophe. Thus far, population growth has been essentially geometric as Malthus
predicted. The Malthusian catastrophe, however, has not occurred, principally because food supply growth has also been roughly
geometric, not arithmetic. Furthermore, the widespread use of contraception and abortion (Malthusian vices) have, as Malthus said
they could, restrained population growth significantly. In fact currently food supply per person is several times higher than
when Malthus wrote his essay.
Neo-Malthusian theory
Neo-Malthusian theory argues that unless at or below subsistence, a
population's fertility will tend to move upwards. Assume for example that a country has 10 breeding groups. Over time this
country's fertility will approach that of its fastest growing group in the same way that will eventually come to resemble
regardless of how large a is or
how small b is. Under subsistence conditions the fastest growing group is likely to be that group progressing most rapidly in
agricultural technology. However, in above-subsistence conditions the fastest
growing group is likely to be the one with the highest fertility. Therefore the fertility of the country will approach that of
its most fertile group. This, however, is only part of the problem.
In any group some individuals will be more pro-fertility in their beliefs and practices than others. According to
neo-Malthusian theory, these pro-fertility individuals will not only have more children, but also pass their pro-fertility on to
their children, meaning a constant selection for pro-fertility similar to the constant evolutionary selection for beneficial
genes (except much faster because of greater diversity). According to neo-Malthusians, this increase in fertility will lead to
hyperexponential population growth that will eventually outstrip growth in economic production. Neo-Malthusians argue that
although adult immigrants (who, at the very least, arrive with human
capital) contribute to economic production, there is little or no increase in economic production from increased natural
growth and fertility. Neo-Malthusians argue that hyperexponential population growth has begun or will begin soon in developed
countries.
Non-occurrence of the catastrophe
At the time Malthus wrote, most societies had populations at or near their agricultural limits. But by the late 20th century, the new agricultural technologies of the green revolution had greatly expanded agricultural production throughout
the world, and what famines still occurred were largely caused by war or political unrest rather than crop failure.
In addition, most technologically developed countries had by this time passed through the demographic transition, a complex social development in which
total fertility rates drop drastically in response to lower
infant mortality, more education of women, increased
urbanization, and a wider availability of contraception. By the end of the
20th century, these countries could avoid population declines only by permitting large-scale immigration. On the assumption that the demographic transition would spread to less developed countries, the United Nations Population Division estimated that human population would peak in the
late 21st century rather than continue to grow until it exhausted available
resources.
Another problem is that there is no strong evidence that the human population - nor any real population - actually follows
exponential growth. In plant or animal populations that are
claimed to show exponential growth, closer examination invariably shows that the supposedly exponential part is actually the
lower limb of a logistic curve, or a section of a Lotka-Volterra cycle. Also, examination of records of estimated
total world human population [1] , [2] shows at best very weak evidence
of exponential growth:
Clearly this is close to linear. In fact, the correlation
coefficient is practically the same for linear growth, or very slow exponential growth (with a characteristic time of about
60 years).
The annual increase graph is worse; for exponential growth, it should itself be an upward trending exponential curve whereas
it has actually been trending downward since 1986. Also the rate of increase should
increase, whereas, of the increase between 1960 and today, five-sixths occurred in the
early 1960s (presumably attributable to the Green revolution); it then rose to a peak in 1989 and has since
declined to levels actually lower than 1970.
Though short-term trends, even on the scale of decades or centuries, do not necessarily disprove the underlying mechanisms
promoting a Malthusian catastrophe over longer periods, the relative prosperity of the human population at the beginning of the
21st century and the apparent failure of spectacular predictions of mass starvation or ecological collapse made by activists such
as Paul Ehrlich in the 1960s and
1970s had led many people, such as economist Julian Simon, to question its inevitability.
See also
External links
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