Jared Diamond would say that Social Darwinism is an absurd theory.
Social Darwinism argues that some societies are more fit than others and these are the societies that become rich and powerful. It argues that the societies that become more advanced have better values and better attitudes. These values and attitudes allow them to succeed.
Diamond says this is ridiculous. He says that what determined whether a society became strong was its geographic location. He argues over and over again that the "backwards" societies did not have (for example) bad attitudes towards adopting agriculture or domesticating animals. Instead, they happened to be in places where agriculture was impossible or where there were very few domesticable plants or animals.
Social Darwinism argues that societies get ahead because of their values and attitudes. Diamond argues that societies got ahead because of their geographic luck.