Today, the phrase "survival of the fittest" is widely used in popular literature for many topics, not just those related to biology. It has widely been used both by people who are in favour of Social Darwinism and those who are against it. It has also been used to talk about competition of all kinds. Popular literature often uses the phrase as a catchphrase. All such extensions of a metaphor need to be watched carefully. They may preserve the original meaning, or they may not.