The renowned Cold Spring Harbor Laboratory, where Watson served as chancellor, also suspended his administrative responsibilities Thursday following the outcry, the laboratory said in a news release.
And London's Science Museum canceled a sold-out lecture he was to give there Friday.
Watson has a history of provocative statements about social implications of science. But several friends said Thursday he's no racist.
A profile of Watson in the Sunday Times Magazine of London quoted him as saying that he's "inherently gloomy about the prospect of Africa" because "all our social policies are based on the fact that their intelligence is the same as ours - whereas all the testing says not really."
While he hopes everyone is equal, "people who have to deal with black employees find this is not true," Watson, who won a Nobel Prize in 1962 for co-discovering the structure of DNA, is quoted as saying. He also said people should not be discriminated against on the basis of color, because "there are many people of color who are very talented."
The comments, reprinted Wednesday in a front-page article in another British newspaper, The Independent, provoked a sharp reaction.
The mayor of London, Ken Livingstone, said his comments "represent racist propaganda masquerading as scientific fact.... That a man of such academic distinction could make such ignorant comments, which are utterly offensive and incorrect and give succor to the most backward in our society, demonstrates why racism still has to be fought."
"I think these remarks are extremely dangerous and extremely offensive to make," Steven Rose, a neuroscientist and a co-founder of the British Society for Social Responsibility in Science, told CBS News correspondent Mark Phillips. "They distress black people; I think quite rightly, too. And they do no good either scientifically or to the fight against racism, in Britain or the United States."
In the United States, the Federation of American Scientists said it was outraged that Watson "chose to use his unique stature to promote personal prejudices that are racist, vicious and unsupported by science."
And Watson's employer said he wasn't speaking for the Cold Spring Harbor research facility on Long Island, where the board and administration "vehemently disagree with these statements and are bewildered and saddened if he indeed made such comments."
"I am mortified about what has happened," Watson said. "More importantly, I cannot understand how I could have said what I am quoted as having said.
London's Sunday Times says it has the recording, reports CBS News correspondent Larry Miller.
Watson is in Britain to promote his new book, "Avoid Boring People," and a publicist for his British publisher provided this statement Thursday to The Associated Press:
"I can certainly understand why people, reading those words, have reacted in the ways they have. To all those who have drawn the inference from my words that Africa, as a continent, is somehow genetically inferior, I can only apologize unreservedly. That is not what I meant. More importantly, from my point of view, there is no scientific basis for such a belief."
Watson's publicist, Kate Farquhar-Thomson, would not address whether Watson was suggesting he was misquoted. "You have the statement. That's it, I'm afraid," she said.
Watson's new book also touches on possible racial differences in IQ, though it doesn't go as far as the newspaper interview.
In the book, Watson raises the prospect of discovering genes that significantly affect a person's intelligence.
"...There is no firm reason to anticipate that the intellectual capacities of peoples geographically separated in their evolution should prove to have evolved identically," Watson wrote. "Our wanting to reserve equal powers of reason as some universal heritage of humanity will not be enough to make it so."
Watson is no stranger to making waves with his scientific views. In 2000, in a speech at the University of California, Berkeley, he suggested that sex drive is related to skin color. "That's why you have Latin lovers," he said, according to people who attended. "You've never heard of an English lover. Only an English patient."
Some years earlier he was quoted in a newspaper as saying, "If you could find the gene which determines sexuality and a woman decides she doesn't want a homosexual child, well, let her."
"Jim has a penchant for making outrageous comments that are basically poking society in the eye," Dr. Francis Collins, director of the National Human Genome Research Institute, said Thursday.
Collins, who has known Watson for a long time, said his latest comments "really ... carried it this time to a much more hurtful level."
In a brief telephone interview, Collins told The AP that Watson's statements are "the wildest form of speculation in a field where such speculation ought not to be engaged in." Genetic factors for intelligence show no difference from one part of the world to another, he said.
Several longtime friends of Watson insisted he's not a racist.
"It's hard for me to buy the label 'racist' for him," said Victor McElheny, the author of a 2003 biography of Watson, whom he's known for 45 years. "This is someone who has encouraged so many people from so many backgrounds."
So why does he say things that can sound racist? "I really don't know the answer to that," McElheny said.
Mike Botchan, co-chair of the molecular and cell biology department at the University of California, Berkeley, who's known Watson since 1970, said the Nobelist's personal beliefs are less important than the impact of what he says.
"Is he someone who's going to prejudge a person in front of him on the basis of his skin color? I would have to say, no. Is he someone, though, that has these beliefs? I don't know any more. And the important thing is I don't really care," Botchan said.
"I think Jim Watson is now essentially a disgrace to his own legacy. And it's very sad for me to say this, because he's one of the great figures of 20th century biology."