Ever since the Nobel prize winner James D. Watson asserted six weeks ago that Africans have innately lower intelligence, fervid debates about race, genes and I.Q. have sprung up on the Web, in publications and in conference rooms.

But in recent days, along with long-simmering arguments over evidence, have come others about whether the topic is even worth studying, or whether it can be discussed openly without spurring charges of racism.

“It’s a subject that almost dare not speak its name,” said Howard Husock of the Manhattan Institute, a conservative research group, as he introduced a debate Wednesday night between James R. Flynn, the author of a new book “What Is Intelligence?” (Cambridge University Press), and Charles Murray, a co-author of “The Bell Curve,” the controversial 1994 book about intelligence that set off a previous free-for-all on race, genes and I.Q.

The risk of giving ammunition to racists or undercutting principles of equality hovers over such conversations like an uninvited dinner guest. That unwelcome visitor has been loitering at the online magazine Slate since last week, when it ran a three-part series arguing that hard science is showing that blacks’ I.Q. scores are lower than those of whites — and whites’ scores are lower than those of Asians — because of genetically based differences in intelligence.