Gene tests prove that we are all the same under the skin

Racists’ central argument and theories linking intelligence to ethnic origin have been destroyed

The popular notion that skin colour can indicate physical or mental differences between groups of people has been demolished by a new analysis of the human genome, which declares race to be a biologically meaningless concept.

Every human being shares more than 99.9 per cent of their DNA with everybody else, and the tiny variations that remain differ more within ethnic groups than between them, a major review of the evidence says.

It is impossible to look at people’s genetic code and deduce whether they are black, Caucasian or Asian, and there is no human population that fits the biological definition of a race, the study found.

Ethnicity is almost entirely socially and culturally constructed, and even the trait used most commonly to define it — skin colour — varies widely among people of similar ancestry.

The findings destroy the central argument of white supremacists and other racist groups, and refute controversial theories that attempt to link intelligence or criminality to ethnic origin.

Standard concepts of race, indeed, are so misleading that they are undermining efforts to untangle the true contribution that genetics make to individuality, and ought to be abandoned by science, the researchers said.

In medicine, for example, race is often used to predict whether patients will respond to particular drugs. While this can be true on average, it leads to generalisations that deny useful medicines to millions who do not meet ethnic stereotypes.

The results have emerged from a comprehensive survey of the science of human variation published today in a special issue of the prestigious journal Nature Genetics.

The research was organised by Howard University in Washington DC, a historically black college where most of the students and academics are African-American, and other contributors included Francis Collins, a leading architect of the Human Genome Project.

Charmaine Royal and Georgia Dunston of Howard University, who led the study, said that the mapping of the human genetic code had forced a “paradigm shift” on the science of race, in which old concepts and definitions were no longer up to the job.

“Existing biological models or paradigms of ‘racial’ and ‘ethnic’ categorisations cannot accommodate the uniqueness of the individual and universality of humankind that is evident in new knowledge emerging from human genome sequence variation research,” they said.

“The term ‘race’, as applied to humans, is incorrectly used. Traditional ‘racial’ designations in humans are not bounded, discrete categories but are fluid, socially defined constructs.”

The human genome map has shown that if two people of any ethnic origin are selected at random, only between 1 in 1,000 and 1 in 1,500 of their genes will differ. This makes our species among the most homogeneous known to science: populations of chimpanzees and fruit flies differ much more from one another in genetic terms. A typical Caucasian’s genes will be as similar — and as different — to those of another Caucasian as they will be to a black African or a Chinese person.

About 90 per cent of genetic variation occurs within ethnic groups, rather than between them. Two Africans, though both superficially “black”, will differ more from one another than from other races. This reflects the course of evolution.

Most scientists now accept that Homo sapiens emerged first in Africa, before a small group, perhaps numbering just a couple of hundred people, left about 40,000 years ago and spread through the rest of the world.

There has not been enough time for human races to diverge much in genetic terms, even before interbreeding is taken into account. “Of special importance to discussions of race, our species has a recent, common origin,” said Charles Rotimi of Howard University. “Race” was a legitimate taxonomic concept that worked for chimpanzees, but not for humans. Dr Collins said race was particularly misleading when applied to medicine.

Some ethnic groups have higher rates of certain diseases or respond less well to certain medicines. These effects, however, are true only on average, and it is individual genetic makeup that really matters. Doctors who take a race-based approach risk misdiagnosing disease or ruling out medicines that would do individual patients good.

Nature Genetics said in its editorial: “The use of race as a proxy is inhibiting scientists from doing their job of separating and identifying the real environmental and genetic causes of disease.”

Research has also shown that when scientists try to guess a person’s ethnic origin by looking at genes, they get it wrong between a third and two thirds of the time.

Another study in the project showed that skin pigmentation is also a poor marker of genetic origin, with significant overlap between populations that society classifies as different races.

Lynn Jorde and Stephen Wooding of the University of Utah said: “Race remains an inflammatory issue, both socially and scientifically. Fortunately, modern human genetics can deliver the salutary message that human populations share most of their genetic variation and that there is no scientific support for the concept that human populations are discrete, non-overlapping entitites.”

WE SEEM TO HAVE RATHER A LOT IN COMMON

• Human Genome Project and rival company Celera both completed draft maps of the human genetic code in 2001, which showed that humans have about 30,000 genes — many fewer than the 100,000 once thought
Research published last week claimed that the number of genes was even lower, about 22,300 — fewer than the plant Arabidopsis

• People share about 99.9 per cent of their DNA with each other, 98.5 per cent with chimpanzees, three quarters with dogs, half with fruit flies and a third with daffodils

• Spin-off projects include the Cancer Genome Project — to find tumour-causing genes — and the Haplotype Map — to find the genetic variants involved in other diseases

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