Who is most associated with the concept of 'survival of the fittest'?

The phrase "survival of the fittest" is most closely associated with Charles Darwin, though the term itself was popularized by philosopher Herbert Spencer. Darwin's theory of natural selection posits that individuals with traits that are better suited to their environment are more likely to survive and reproduce. This concept is fundamental to the understanding of evolutionary biology.

Darwin's observations during his studies, particularly on the Galápagos Islands, led him to conclude that species evolve over time through a process where advantageous traits become more common in successive generations. This idea laid the foundation for modern evolutionary theory.

While Huxley contributed significantly to the discussion of evolution and acted as a prominent advocate of Darwin's theories, he is not the originator of the concept. Lamarck is known for his own theory of evolution, which emphasized the inheritance of acquired characteristics, a concept different from natural selection. Wallace independently arrived at similar conclusions regarding evolution, but it was Darwin who first articulated the mechanisms of natural selection that encompass the idea of "survival of the fittest."