Invasion of The Body Snatchers was released in 1956 during a time where the American Dream was a house in the suburbs with a wife and kids. Everybody fit into society then. The only real fears were communism, the system of government of the Soviet Union during this time period, McCarthyism, which was the gripping fear in the U.S., started by U.S. Senator Joe McCarthy, that people you knew could be a communist sympathizer, communist themselves, or even a spy.
Through analysis of the movie and the book from which it was based on (Body Snatchers, Jack Finney) many people have come up with different interpretations of what the theme of the movie was. McCarthyism, communism, and the ideas of conformity and central thinking are all among the speculated themes. It is my belief that all of these themes come together in a fashion that refutes 1950s ideology.
One of the most fervently believed themes is that the movie is a metaphor or allusion to communism. Communism is a system of government where the central government basically controls everything. From business, to a work-man's wages, to obviously the laws that govern society. The ideal was that everybody would be equal. Equal in work wages, home life. If everybody was equal then there would be no envy or jealousy or need for conflict, creating a utopian society. .
The whole idea of a perfect society or a group mind (or government) is represented throughout the movie by the pod people. They think and act as one unit with orders coming from some sort of a central consciousness, all of them becoming equal but becoming emotionless in the process. What many people, I included, believe that this movie is a warning of the dangers of communism and the dangers and fears that it brings. Furthermore I believe that Steve Finney capitalized on that fear to make this movie.
Yet another one of the strong beliefs of the theme of the movie was that is was symbolic of McCarthyism.