Who proposed the idea that societies are improved by the principle of "the survival of the fittest"?

Jane Addams was a pioneering social worker and reformer known for her work in social justice and women's rights. While she focused on improving social conditions and advocating for the marginalized, she did not contribute to the concept of "survival of the fittest" or its application to societal improvement.

Max Weber was a prominent sociologist known for his studies on bureaucracy, authority, and the relationship between religion and economics. Although he made significant contributions to sociological thought, Weber did not advocate for the "survival of the fittest" principle and instead emphasized the role of culture and social structures in shaping society.

Karl Marx was a philosopher and economist known for his critique of capitalism and the class struggle. He focused on the dynamics of class relations and economic systems rather than the individualistic competition inherent in Spencer's "survival of the fittest." Marx's theories emphasized collective action over individual survival.