While there were plenty of individual conservatives who advocated for it, pre-war it was mostly a progressive cause.
It's hard to understand now, but society back then was quite different than today, and the political divisions of the time were also different. Francis Galton had done some early psychometry, and published his results claiming that the English upper class was the upper class because they were genetically superior to the lower classes. This result was widely accepted by both the progressives and the conservatives. The difference between the left and the right was not opposition to the principle of Social Darwinism, but just what should be done about it. The progressives advocated for eugenics to lift the lower classes from the 'genetic deficit' they were born into, while the traditional conservatives believed that this was unnecessary and that the situation as it existed was the natural order that shouldn't be fixed. Neither side would fit at all into modern common morality.
It's hard to understand now, but society back then was quite different than today, and the political divisions of the time were also different. Francis Galton had done some early psychometry, and published his results claiming that the English upper class was the upper class because they were genetically superior to the lower classes. This result was widely accepted by both the progressives and the conservatives. The difference between the left and the right was not opposition to the principle of Social Darwinism, but just what should be done about it. The progressives advocated for eugenics to lift the lower classes from the 'genetic deficit' they were born into, while the traditional conservatives believed that this was unnecessary and that the situation as it existed was the natural order that shouldn't be fixed. Neither side would fit at all into modern common morality.