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Darwin and Malthus

After being mobbed in their carriage by poor, starving people, Charles and Erasmus Darwin are prompted to consider the human struggle for existence. As they discuss Malthus's assertion that human population would skyrocket if not for natural controls such as famine and disease, Charles has a new insight: other animals' populations must also be kept low by a struggle for existence, in which only the best adapted survive. The theory of natural selection is born. From Evolution: "Darwin's Dangerous Idea"

Credits: 2001 WGBH Educational Foundation and Clear Blue Sky Productions, Inc. All rights reserved.

Darwin and Malthus

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The Age of Darwin

Backgrounder

Darwin and Malthus:

The year was 1838. In England, the Industrial Revolution was under way, but it had made rich only the owners of production, not the workers. In increasingly crowded cities, ordinary people struggled for their daily existence. Some of the poor rioted. The Poor Laws were under attack: Welfare to the needy would only increase their dependence and encourage the breeding of still more hungry mouths to feed, said critics. It was in this pivotal year that Darwin, back from his voyage on the Beagle and trying to understand the forces that drove the origin of new species, read the works of Thomas Malthus, a parson and social economist.

In opposition to the utopian thinkers of the day, Malthus believed that unless people exercised restraint in the number of children they had, the inevitable shortfall of food in the face of spiraling population growth would doom mankind to a ceaseless struggle for existence. Out of that unforgiving battle, some would survive and many would not, as famine, disease, and war put a ceiling on the growth in population.

These ideas galvanized Darwin's thinking about the struggles for survival in the wild, where restraint is unknown. Before reading Malthus, Darwin had thought that living things reproduced just enough individuals to keep populations stable. But now he came to realize that, as in human society, populations bred beyond their means, leaving survivors and losers in the effort to exist.

Immediately, Darwin saw that the variation he had observed in wild populations would produce some individuals that were slightly better equipped to thrive and reproduce under the particular conditions at the time. Those individuals would tend to leave more offspring than their fellows, and over many generations their traits would come to dominate the population. "The result of this would be the formation of new species," he wrote later. "Here, then, I had at last got a theory by which to work."

That theory, of course, was none other than natural selection, the driving force of evolution. Though scholars have debated just how influential Malthus was in Darwin's thinking, there can be no doubt that his view of the struggle in society enabled Darwin to appreciate the significance of the struggle in the wild.

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