Although they were commonly called "social darwinists," advocates of economic, national, or racial "survival of the fittest" ideas actually drew less on biologist charles darwin than on:

Herbert Spencer and William Graham Sumner

Explanation:

Social Darwinism is a theory that states that humans go through the same laws of natural selection as the one that animals and plants go through, a theory proposed originally by Charles Darwin in his "survival of the fittest" phrase.

However, Herbert Spencer, British philosopher and scientist, proposed that "humans in society also go through a struggle for existence as the 'survival of the fittest'". Similar to Darwin, he stated that natural selection acts on the survival of the individuals who are good competitors. Moreover, William Graham Sumner stands out amongst the most important and influencial Social Darwinists that were once inspired by Spencer.

Therefore, advocates of economic, national, or racial "survival of the fittest" ideas actually drew less on biologist Charles Darwin than on Herbert Spencer and, frequently, on W. Graham Sumner as well.