ATLANTA -- Other than skin color, what separates black people from white?
Not much, a growing number of scientists say. In fact -- genetically speaking -- there is no such thing as race.
Such a startling conclusion is emerging from studies undertaken by a Stanford University researcher and others on genetic diversity in human populations.
"I find the term 'race' pretty useless," Luca Cavalli-Sforza, a Stanford population geneticist, told reporters Sunday during the annual meeting of the American Association for the Advancement of Science.
Evidence from his own studies and those of others is mounting that what we think of as "race" is only skin-deep -- and below the surface lies a range of genetic variability that shows no link to skin color or other superficial physical traits.
For example, the sickle cell anemia trait, long viewed as something found in black people, has also been found among some Southern Europeans as well as Africans, but is not found in some South African tribes. The Rh negative blood type is found most often in the Basque people of France and Spain, and also surfaces among North Africans but not South Africans.
Mr. Cavalli-Sforza's studies raise a fundamental challenge to claims in a recent best seller, "The Bell Curve," that genetics explains why black people score lower on IQ tests than whites. The best seller has become a lightning rod for arguments about whether some government programs that serve a high proportion of low-income blacks are doomed to failure and should be abandoned.
Researchers meeting Sunday wasted no time in denouncing such genetic claims as scientifically weak.
"We have no basis to claim there is any genetic basis for differences in intelligence in any racial group," said Joseph Graves, a geneticist from the University of Arizona.
Mr. Cavalli-Sforza, in a recent book on human genetic diversity that synthesizes 50 years of research in population genetics, found such a wide range of genetic variation in both African and non-African groups that it makes the conventional notion of race meaningless.
In short, looks can be deceiving.
"There are some superficial traits like skin color and body build," Mr. Cavalli-Sforza said Sunday. "They are striking, and we notice them.
"That is what misleads us. It makes us think races are very different. They are not, when we look under the skin."
Mr. Cavalli-Sforza found that the genetic diversity of populations was better explained by geographic origin than by skin color. His book includes more than 500 maps color-coded to show areas of genetic similarity.
He found the biggest genetic differences between African and Australian populations. Yet many Australian aborigines have skin as black as Africans.
Commenting on the notion that genetics has made one race more intelligent than another, Mr. Cavalli-Sforza has said previously: "The truth is that there is no documented biological superiority of any race, however defined."
Skin color or facial characteristics of Asian people, for example, have developed over time as a response to climate. Black skin protects against strong sunlight. A flat nose and eyelid skin folds seen in Asians are adaptations to freezing weather of Siberian populations.
But none of these superficial adaptations shows a link to other underlying genetic traits, Mr. Cavalli-Sforza said.
Mr. Cavalli-Sforza is not the first to reveal the scientific weakness of categorizing people by skin color. Accumulating evidence had already prompted the American Association of Physical Anthropologists to declare that "pure races" do not exist now -- and probably never did.
"Biologically . . . the use of race is no longer a valid scientific concept," said Solomon Katz, a physical anthropologist at the University of Pennsylvania. "We're putting it to rest after so many years."
Yet all these scientists agreed Sunday that the term "race" may have valid social meaning even if it isn't biologically based. Most people would find life confusing if they couldn't identify somehow with a group.