Research into population genetics



While not exactly a top selling book,The History and Geography of Human Genes is a remarkable collection of more than 50 years of research in population genetics.It stands as the most extensive survey to date on how humans vary at the level of their genes.the book's firn conclusion:once the genes for surface features such as the skin colorv and height are discounted.the "races" are remarkably under the skin.the variation among individuals is much greater than the difference among groups.in fact there is no scientific basis for theories pushing the genetic superiority of any one population over another.



The book,however,,is much more than an argument against the latest racially biased theory.The prime mover behind the project ,Luca Cavalli-sforza,a standford professor,labored with his colleagues for 16 years to create nothing less than the first genetic similarity _muchasplaces of equal altitude are shown by the same color on other maps .By measuring how closely current populations are related,the authors trace the routes by which early humans migrated around the earth.Result:the closest thing we have to a global familly tree.The imformation needed to draw that tree is founded in human blood :various proteins that serve as makers to reveal a person's genetic makeup.Using data collected by scientists over decades,the authors assembled profiles lof hundreds of thousands of indiduals from almost 2,000 groups.And to ensure the populations were "pure",the study was confinede to groups that were in their present locations as of 1492,before the first major movements from Europe began_in effect ,a genetic photo of the world when Columbus sailed for America.



Collecting blood ,particularly from ancient vpopulation in remote areas ,was not always easy;potential donors were often afraid to cooperate,or raised religious concerns .On one occasion,when Cavalli-sforza was taking blood samples from children in a rural region of Africa,he was confronted by an angry farmer waving an axe.Recalls the scientist:"I remember him saying ,"If you take the blood of the children ,I 'll take yours."He was worried that we might want to do some magic with the blood."



Despite the difficuties,the scientists made some remakable discoveries .One of them jumps right off the book's cover:a color map of the world's genetic variation has Africa at one end of the range and Australia at the other.Because Australia's native people and blake Africans share such super ficial characteristics as skin color and body shape.they were widely assumed to be closely related .But their genes tell another story.Of all humans,Australians are most distant from the Africans and most resemble their neighbors,the Southeast Asians.What the eye sees as racial differences--------between Europeans and Aficans ,for example------are mainly a way to to adapt to climate as humans move from one continent to another.



The same map,in combination with ancient human bones,conforms that Africa was the birthplace of humanity and thus the strating point of the original human movements.Those findings,plus the genetic distance between present-day and none- Africans,indicate that the split from the African branch is the oldest on the human family tree.

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