EVOLUTION:


Definition:

Evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection.

PRE-HISTORIC DEVELOPMENT OF THEORY:

In the early 19th century Jean-Baptiste Lamarck (1744 – 1829) proposed his theory of the transmutation of species, the first fully formed theory of evolution. In 1858 Charles Darwin and Alfred Russel Wallace published a new evolutionary theory, explained in detail in Darwin's On the Origin of Species (1859). The theory of evolution by natural selection, first formulated in Darwin's book "On the Origin of Species" in 1859, is the process by which organisms change over time as a result of changes in heritable physical or behavioral traits.


MALTHUS PRINCIPLE OF POPULATION:


In his 1798 work, An Essay on the Principle of Population, Malthus examined the relationship between population growth and resources. From this, he developed the Malthusian theory of population growth in which he wrote that population growth occurs exponentially, so it increases according to birth rate. Malthus wrote:

That the increase of population is necessarily limited by the means of subsistence,
That population does invariably increase when the means of subsistence increase, and,
That the superior power of population is repressed by moral restraint, vice and misery.

Malthus criticized the Poor Laws for leading to inflation rather than improving the well-being of the poor. He supported taxes on grain imports because food security was more important than maximizing wealth.  His views became influential, and controversial, across economic, political, social and scientific thought. Pioneers of evolutionary biology read him, notably Charles Darwin and Alfred Russel Wallace. He remains a much-debated writer.

1. Population and Food Supply

Thomas Malthus theorized that populations grew in geometric progression. A geometric progression is a sequence of numbers where each term after the first is found by multiplying the previous one by a fixed, non-zero number called the common ratio. For example, in the sequence 2, 10, 50, 250, 1250, the common ratio is 5.

Additionally, he stated that food production increases in arithmetic progression. An arithmetic progression is a sequence of numbers such that the difference between the consecutive terms is constant. For example, in series 2, 5, 8, 11, 14, 17, the common difference of 3. He derived this conclusion due to the Law of Diminishing Returns.

From this, we can conclude that populations will grow faster than the supply of food. This exponential population growth will lead to a shortage of food.

2. Population Control

Malthus then argued that because there will be a higher population than the availability of food, many people will die from the shortage of food. He theorized that this correction would take place in the form of Positive Checks (or Natural Checks) and Preventative Checks. These checks would lead to the Malthusian catastrophe, which would bring the population level back to a ‘sustainable level.’

A. Positive Checks or Natural Checks

He believed that natural forces would correct the imbalance between food supply and population growth in the form of natural disasters such as floods and earthquakes and human-made actions such as wars and famines.

 B. Preventative Checks

To correct the imbalance, Malthus also suggested using preventative measures to control the growth of the population. These measures include family planning, late marriages, and celibacy.



CRITICISM OF MALTHUSIAN PRINCIPLE OF POPULATION:


1. Population Growth

The gloom and doom forecasts put forward by Malthus have not played out. In Western Europe, populations have grown (not at the rate Malthus predicted) and food production has also risen because of technological advancements.

2. Food Production

Thanks to many technological advancements, food production has dramatically increased over the past century. Often, the food production rate has grown higher than the population growth rate. For example, during the 1930s in the US, 25% of the population worked in the agricultural sector while the total GDP was less than $100 billion to the GDP. Today, less than 2% of the population works in the agricultural sector while the total GDP is over $14 trillion.

3. Global Trade

The limited availability of land at the time was the basis for Malthus’ theory on food production constraints. However, thanks to globalization we can trade good and services for food, which increases the amount of food a country can consume.

4. Calculations

Malthus did not provide calculations for the geometric growth of populations and the arithmetic growth of food. Since then, experts have pointed out that the growth rates are not consistent with Malthus’ predictions.