Two scientists took to the pages of The Guardian yesterday to contend that their area of expertise, which has been called interpretative phyleogeography is not "genetic astrology," in response to another recent column which said that it may be.
According to Martin Richards, a professor of archaeogenetics at the University of Huddersfield, and Vincent Macaulay, a reader in statistics at the University of Glasgow, they engage in interpretative phyleogeography when they look to mitochondrial DNA and the Y chromosome to study the dispersal of humans.
They were responding to criticisms leveled by Mark Thomas, a professor of evolutionary genetics at University College London, in the same paper two months ago, in which he suggested that the genetic ancestry testing industry, and the media which has been enabling them, are mostly offering a load of hooey.
Thomas had taken the UK media to task for television shows like "Meet the Izzards," in which the ancestral genetics of comedian Eddie Izzard shows him to have a Viking descendant on his mum's side and an Anglo-Saxon on his fathers. Another example, he said, was the recent article in the Daily Telegraph which said that as many as 1 million British men may be directly descended from the Roman legions.
He also said that the results from the genetic ancestry testing products that some of these media reports are based on are convoluted by the complexity of the science.
"The truth is that there is usually little scientific substance to most of them and they are better thought of as genetic astrology," Thomas writes.
Thomas says that if anyone looks very far back in time they will find that they have more ancestors than they have sections of DNA, and that humans move around a lot, making predictions about lineages a difficult business.
If you go back around 5,000 years, he adds, you get to a point where either nearly everybody alive then was a common ancestor of nearly everyone alive today, or they were a common ancestor to no one alive today.
"Nobody is pure this, or pure that, and a substantial proportion of human ancestry is common to all of us. Ancestry is complicated and very messy," Thomas writes.
Richards and Macaulay agree that Thomas "may have a point in his critique of his genetic testing companies," but also say that there are real merits to linking genetics and geography to study ancestry.
Phylogeographers, they write, rely on "the principle that every mutation in the DNA arises at a specific point in space and time, and that a plot pinpointing these locations is effectively an outline of the movement of people across the landscape and around the world."
They also note that "the mitochondrial picture almost exactly matches the archaeological evidence for the colonization of the Remote Pacific, about 3,000 years ago," and that the same is true from the Bantu expansion in Africa.
"Hopefully, the point is made. There are enough archaeologically well-known cases of colonization to show that phylogeographic interpretations can work in principle," they write.