This is an extremely studied question, and The Bell Curve operates in the phlogiston era of this science. The idea that this is a forbidden topic only whispered about in the academy is an Internet myth.

Most of the reason you don't hear about current research into behavioral genetics is that a, uh, very particular excitable subset of Internet commenters are actually interested in this research, and the research results aren't coming out the way they want them to.

(You can get an isomorphic answer substituting psychometrics for behavioral genetics; this is the "twin studies" line of research that Richard Herrnstein relied on in the book, and it too is actively studied, but not talked about because the answers don't come out the way --- let's call them "Herrnstein fans" --- want them to).