Who used the term "survival of the fittest"?

Explanation

Herbert Spencer is credited with coining the phrase 'survival of the fittest' in his work Principles of Biology, published in 1864. He used this phrase to explain the process of natural selection described by Darwin, emphasizing that organisms better adapted to their environments are more likely to survive and reproduce. While Darwin's theory of natural selection underpins the concept, he did not initially use this exact phrase. Lamarck's ideas, predating Darwin, focused on acquired characteristics, not survival of the fittest. Aristotle's contributions to biology predate evolutionary theory entirely.