There’s a long history of discussion about what exactly intelligence is, how whatever it is is measured, and why some social groups have statistically higher scores than others. Here’s an easy place to start looking into it:
The Wikipedia article raganwald kindly linked to has an archived set of talk pages that go on almost endlessly, as the article has long been the subject of edit-warring. That article and related pages have been the subject of an Arbitration Committee case (opened at about the time I became a wikipedian, by coincidence)
with ongoing administrative sanctions. In other words, I'm not sure if the article is currently in good enough shape to recommend. The Wikipedia user bibliography "Intelligence Citations"
