Population theories are essential for comprehending the dynamics of human population growth as well as the effects of population growth on the environment. The Biological Theory of Population is one of the earliest and most influential population theories. This theory explains population growth using biological factors such as fertility, mortality, and migration.
Historical Development of Biological Theory of Population
The Biological Theory of Population or Malthusian Theory of Population can be traced back to Thomas Malthus‘s famous essay “An Essay on the Principle of Population,” published in 1798. According to Malthus, population growth will inevitably outstrip food production, resulting in famine, disease, and war. His theory was the basis for the Biological Theory of Population.
Explanation of the Biological Theory of Population
The Biological Theory of Population holds that biological factors such as fertility, mortality, and migration determine population growth. According to this theory, the population of a species will grow exponentially if the birth rate exceeds the death rate. If the death rate exceeds the birth rate, the population will shrink.
Assumptions of the Biological Theory of Population
The Biological Theory of Population makes several assumptions, including:
- All individuals within a species have the same fertility and mortality rates.
- The environment can support a limited number of individuals, and the availability of resources such as food and water will control the population.
- Population growth is determined solely by biological factors and is independent of social, economic, and cultural factors.
- There is no migration in or out of the population.
Main propositions and explanation of biological theory of population
Reverend Thomas Malthus developed the biological theory of population, also known as the Malthusian theory of population, in the late 18th century. The theory holds that population growth will inevitably lead to resource depletion, resulting in poverty, famine, and other social unrest. Malthus argued that population growth would always outstrip resources’ ability to support it, resulting in a “natural” check on population growth, such as war, disease, and starvation.
The main propositions of the biological theory of population are as follows:
- Population grows at a geometric rate: According to Malthus, population can grow exponentially, but resources required to support that population can only grow at an arithmetic rate.
- The food supply is limited: The available resources, such as arable land and technology, limit the amount of food produced.
- Population growth will eventually outstrip food supply: As the population grows geometrically, it will eventually outnumber the available food supply, resulting in famine, disease, and other forms of social unrest.
- Population control is necessary: Malthus believed that population control was necessary to prevent resource depletion and suffering caused by overpopulation.
Malthus proposed two types of checks that would help control population growth:
- Positive checks: These are natural checks that result from increased mortality rates due to famine, disease, and war.
- Preventive checks: These are voluntary checks on population growth, such as delaying marriage, practicing abstinence or contraception, and reducing family size.
Criticism of the Biological Theory of Population
- Neglects social and economic factors: One of the most common criticisms of the biological theory of population is that it focuses too much on biological factors while ignoring social and economic factors that can influence population growth. Cultural norms, economic development, and access to education and healthcare can all significantly impact fertility rates and population growth, but the biological theory largely ignores them.
- Ignores individual agency: The biological theory of population holds that individuals have little agency or control over their reproductive behavior, and that biological factors such as fertility and mortality rates drive population growth. Individuals, on the other hand, have agency and can choose whether or not to have children. Various social, economic, and cultural factors can influence these choices.
- The relationship between biology and population growth is oversimplified: While biological factors such as fertility and mortality rates influence population growth, the relationship between biology and population growth is far more complicated than biological theory suggests. While high fertility rates, for example, can lead to rapid population growth, they can also respond to high mortality rates and the need for children to support parents in old age.
- Assumes homogeneity of populations: Population biology assumes that populations are homogeneous and that all individuals within a population behave similarly. Individuals within populations, however, have different reproductive behavior, which social, economic, and cultural factors can influence.
- Ignores environmental factors: The biological theory of population neglects the influence of environmental factors on population growth. Environmental factors such as access to clean water, food security, and natural disasters can significantly impact fertility and mortality rates, but the biological theory largely ignores them.
- Justifying eugenic policies: The biological theory of population has been used to justify eugenic policies that control population growth, such as forced sterilization and selective breeding. These policies are frequently based on incorrect assumptions about the relationship between biology and population growth, and they can result in human rights violations.