For many natural scientists, 1859 marks the beginning of the modern era of biology. That's the year Charles Darwin published "The Origin of Species," the book that spelled out the theory of evolution by natural selection. Darwin is such a cultural icon and so closely identified with evolution that it's easy to think that he arrived at his theories in a vacuum. In reality, the father of modern biology was influenced by Thomas Malthus, who published "An Essay on the Principle of Population" in 1798. In fact, it might be said that "The Origin of Species" owes its existence to Malthus and the controversial idea at the heart of his essay.
Before we delve into this idea, we should cover how Malthus, an English economist, came to write his essay. One of the great concerns of 18th and 19th century England was the decline of living conditions, especially in cities such as London and Manchester, where poor laborers lived in slums with inadequate housing and sanitation. As people poured into urban areas, social reformers began discussing the scientific and philosophic aspects of population growth. One such reformer was William Godwin, who wrote a popular book titled "The Enquirer." In it, Godwin described population growth as a beneficial force -- something that could produce more workers and lead to greater wealth and a higher quality of life for all. Malthus disagreed vehemently and, in response, wrote his now-famous essay.
Here's what Malthus asserted: First, he said, food is necessary for humans to survive. Second, human beings enjoy reproducing too much to stop. As we reproduce, our numbers will grow. Unfortunately, population tends to grow exponentially while food production increases only linearly. In other words, population grows at a much faster rate than the amount of food being produced. This disparity in growth rates, Malthus argued, will eventually lead to a population of people who can't be adequately fed. And this, finally, will lead to even more human suffering -- disease, famine, murder.
Find out what linked Malthus to Darwin next.