The first draft of the Human Genome, due to be published early next year, represents only a fraction of the world’s human genetic diversity because the sample used for the project does not include adequate representation from sub-Saharan Africa. With more genetic variation occurring within human races, rather than between them, the project’s exclusion of individuals from the most variable human populations on the planet ignores the worldwide genetic diversity of the human species and our evolutionary history, according to Todd R Disotell an anthropologist from New York University writing in Genome Biology.
Despite our visual perception of the variation between races, studies have shown that as much as 85% of all human variation occurs between individuals of the same population while less than 10% of the variation was between the major races – represented in the broadest sense by Africans, Asians and Europeans. This pattern of diversity is largely accounted for by human evolutionary history. Studies of human DNA from populations around the world suggests a common African ancestry living some 200,000 years ago. Modern theories of human evolution suggest that expansion of populations from Africa began 100,000 years ago - giving nearly twice as much time for variation to accumulate in sub-Saharan Africa as in the rest of the world, writes Disotell.
The announcement by Craig Venter, President and Chief Scientific Officer of Celera Genomics, on June 26 2000 that his research group had assembled the complete human genome should, Disotell argues, "be viewed only as the first step in characterizing human diversity". The Celera research group did not sample a complete human genome, rather they generated a composite genome made up of three females and two males identifying themselves as African-American, Asian, Caucasian and Hispanic. From these data, Celera scientists concluded that, "the concept of race has no genetic or scientific basis" - a quote that was widely cited. These conclusions, while valid, cannot be deduced from the Celera data. "A scientifically more viable strategy would be to examine many more sub-Saharan Africans than non-Africans," writes Disotell, "because sub-Saharan African populations can be expected to represent the majority of all human variation." In addition, Disotell suggests that rather than sampling individuals from a mixed population such as the USA – where household data surveys show that about 20% of the population have close relatives from a racial group different from their own – samples should be gathered from the regions themselves. The genomes of the African-American population, for instance, have a distinct European influence comprising about 7% of the gene pool in Jamaica and as high as 26% of the African-American gene pool in some North American cities.
A controversial project to survey human genetic diversity, the Human Genome Diversity Project, has been proposed in order to represent worldwide genetic diversity. The proposal, still being modified to take into account ethical and legal concerns, would collect together samples from a wide range of populations from throughout the world thought best to represent human diversity and would take into account our evolutionary history and known patterns of variation among current human populations. "A human diversity project has been made far more tractable by the work laid by Celera and the publicly funded Human Genome Organisation’s impressive accomplishments, not only in sequencing ‘the’ human genome but also in beginning to use it as a map to discover the full extent of human genetic diversity," writes Disotell.
The electronic version of this article is the complete one and can be found online at: http://genomebiology.com/2000/1/5/comment/2004
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Featured article:
Human genomic variation
Todd R Disotell, New York University, USA
Genome Biology 2000 1(5): comment 2004.1-2004.2
http://genomebiology.com/2000/1/5/comment/2004
Other Useful Links
Celera Genomics Completes the First Assembly of the Human Genome
http://www.celera.com/corporate/about/press_releases/celera062600_1.html
Craig Venter, President and Chief Scientific Officer of Celera Genomics, remarks at the human genome announcement the White House
http://www.celera.com/corporate/about/press_releases/celera062600_2.html
Angler N: Do races differ? Not really, genes show
New York Times 2000, August 22 F1-F5
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