The bell curve, in which the authors argue that intelligence is quantifiable and that they found differences in intelligence across racial groups, is one of the most prominent examples of in recent decades.

It is one of the most prominent examples of biological racism.
This book was written by Richard J. Herrstein and Charles Murray in 1994, and deals with controversial issues such as how intelligence is different in people based on their race and skin color. According to them, some races are more intelligent than others, which is obviously debatable.