When two rival scientific groups jointly announced in June that they had completed a working draft of the entire sequence of the human genome — the genetic material found in every cell of every human being — the achievement was rightly greeted as a milestone of modern medical research.

Doctors recognized at once that it would have huge implications for the understanding and treatment of genetically determined human diseases. Since then, however, as the enormity of the breakthrough continues to sink in, social scientists and others have pointed out that its significance extends far beyond medicine. The most recent revelation slipped into the news almost unnoticed, but it may eventually prove to be the most revolutionary of all. The genome project, it turns out, undermines a belief dear to the human heart and central to the whole history of human strife: the concept of race.

Everybody knows, or thought they knew, that humanity is divided into races. Merriam-Webster blandly defines the term as denoting a division of mankind possessing traits that are transmissible by descent and sufficient to characterize distinct human types. The old-fashioned labels — Caucasian, Ethiopian, Mongolian, Malayan and so on — have been more or less retired, but their latter-day variants live on in the organization of human beings largely by color: white, black, Asian, Hispanic and others. At its worst, the belief in “distinct human types” has fueled atrocities of the magnitude of Europeans’ enslavement of Africans or the Nazis’ attempt to exterminate Jews, as the right of a “master race” over an inferior one. But it has less malign manifestations, too, so familiar that we may not even notice them, let alone stop to question them. Racial terms appear on official documents like passport or university applications. Laws are passed forbidding discrimination on the basis of race, as if race were an objective, scientific concept.

Below the level of the main supposed racial divisions exist numerous subcategories of ethnicity that are fundamentally racist in their assumptions. Asians can “tell by looking” a Japanese or Chinese or Korean or Filipino face; an Englishman can pick a “potato-faced” Irishman a mile off; a Rwandan Hutu can identify a Rwandan Tutsi at a single murderous glance, and vice versa. There is no denying that human beings come in many different colors, shapes and sizes. The problem is that on the slender foundation of observable physical differences — whether obvious or subtle — totter all kinds of unwarranted assumptions about nonphysical ethnic traits. Thus “Jews” are seen as venal and grasping, the “Chinese” as dishonest, “Filipinos” and “Irish” as stupid, and so on. But a great blow has now been struck for our liberation from such fine and potentially inflammatory distinctions.

From the point of view of a geneticist, whose job it is to track whatever is “transmissible by descent,” such attributes as skin and eye color, stature, hair texture or the size and shape of noses have long been considered insignificant. Just how insignificant was confirmed and enhanced by the completion of the genome-sequencing project, which lays out, as it were, the whole map of transmissible traits. “If you ask what percentage of your genes is reflected in your external appearance, the basis by which we talk about race,” said one U.S. researcher, “the answer seems to be in the range of .01 percent.”

This is the revolutionary statistic, only made possible as the full genetic picture came into focus this year. What it means, quite simply, is that each of us shares 99.99 percent of all that defines us as Homo sapiens with every other person on the planet. The things that we think make us so different from one another — mostly having to do with the way we look — are so superficial as to be biologically irrelevant. We are one race, one species. To get even as far removed as a subspecies, you have to go back in time to Homo neanderthalensis. Homo sapiens, say the scientists who worked on the genome project, just hasn’t been around long enough to evolve and divide into anything they would bother to call races. There is no such thing as unique racial attributes among human beings; our differences, striking as they may seem, are mainly cosmetic.

Because stupidity and prejudice are among the transmissible traits that we all share, naturally we will go on fearing, insulting and squabbling with those who don’t look or sound or smell or act like us. The difference is that for the first time in human history we will not be able to tart up our racism with even a shred of science.

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