In 1841, another English political economist, Thomas Doubleday (1790-1870) propounded what he called the true law of population, which attempted to establish a relationship between population growth and the diet of the people.
According to Doubleday, poverty stimulates population growth, as the diet of the poor is insufficient. He based his principle on the well known fact about the animal world: rabbits and swine’s “will not conceive if fed to a certain height of fatness.”
He maintained that while the Chinese; the Irish and the Scotch were highly fertile because their diet was inadequate, the birth rates in France were low because the French were well-fed.
In 1952, Josue de Castro, in his book, Geography of Hunger, contended that deficiency of proteins make under-nourished people more fertile than those who are well-nourished. He based his conclusions on the negative correlation between the protein content of the diet and the birth rates of various countries.
ADVERTISEMENTS:
Neither the theory of Doubleday, nor that of Castro, has been accepted by demographers, who maintain that fertility variations are associated with business cycles, which are obviously not associated with diet.
Many countries in the West experienced an upsurge in fertility once economic recovery set in (1937-38) following the Great Depression of the early 1930’s.
This phenomenon cannot, of course, be attributed to low protein consumption. Even if it is granted that reproductive capacity is determined by diet, the utilisation of the available food depends on many other social, psychological and economic factors.
In this context, Thomlinson’s remarks on Castro’s theory are very pertinent. He says, “He might as well have considered the correlation between national fertility and consumption of ice-cream soda, use of washing machines or watching of television.”