I saw from the Regular Guy that today is the bicentennial of Lincoln. I see from Google that today is also the bicentennial of Darwin, for that is the bicentenniel they have chosen to commemorate. I can see why. Of the two, Darwin has easily had the larger impact.
Darwinism alone has no practical effects. 'We evolved from apes' alone does not tell anyone how to act, or what we should do now, or how we should go about our daily lives. The theory has nothing to do with morality or ethics. It is only with the application of outside considerations, another set of first principles that we may create practical conclusions. And what practical conclusions have come from Darwin. I'll let James Burke in one of my favourite (if somewhat dated) television shows explain some of the conclusions created using Darwin as justification:
Nazism, Communism, and unrestrained capitalism all claim Darwin as scientific justification for their theories. To these three I would add Eugenics, which inspired one Margaret Sanger, the founder of Planned Parenthood. Add them up, and Darwin's rather innocuous theory has been the justification of many, many times the number of victims to Christ, and in less than two hundred years. The light of science can cast a very, very dark shadow.