""The influence primarily responsible for the modern eugenics movement was the establishment of the doctrine of organic evolution following the publication of Darwin's Origin of Species in 1859." - Samuel J. Holmes, Human Genetics, 1936, chapter 25."
I understand that you wish to discredit the science of evolution by linking it to the political eugenics movement. But Darwin's theory only attempted to explain what happend in the past, not to recommend future behavior.
And here is what other eugenicists said in 1921 were the origins of their movement. Note they did not include either Darwin or evolution:
Wikipedia: Eugenics
Ooooooops -- my mistake. Clearly, evolution was the purpose of eugenics.
But long before the word "evolution" became current, farmers had practiced animal husbantry on their livestock, and aristocrats strove constantly to improve their own "breeding."
They didn't need Darwin to tell them how.