What is the bell curve controversy?

I assume that you are asking about the controversy over the book
The Bell Curve that was published in 1994 by Richard Herrnstein and Charles
Murray. This book argued that there are differences in intellectual ability between social and
racial groups. This book claimed that IQ tests showed clear differences in intelligence between
members of various racial groups.

This led to a huge amount of
controversy because of the fact that it seemed to be suggesting that non-whites are generally
less intelligent than whites. This seemed like a return to the sorts of thinking that promoted
things like segregation and slavery. The controversy, then, centered on the accuracy and meaning
of the authors' findings. The controversy was about whether there really are differences in
intelligence between various races.