Genetic Genealogy Like Astrology?

Maybe If It’s First Generation Sex-Linked Testing, Not Autosomal 

Dust off the crystal ball. Scientists consider DNA ancestry services “genetic astrology,” according to a recent BBC article by Pallab Ghosh. In “Some DNA Ancestry Services Akin to ‘Genetic Astrology’,” Ghosh quotes Professor David Balding as maintaining that ‘“such histories are either so general as to be personally meaningless or they are just speculation from thin evidence.’” One article, “Don’t Believe the Guy Who Claims He’s Descended From Vikings,” quotes evolutionary geneticist Mark Thomas, as saying “these tests have so little rigor that they are better thought of as genetic astrology.”  That may be right about some tests. But the key word is “some.”

Not all DNA ancestry tests or companies are created equal.  It is as much an oversimplification to suggest they are as it would be to claim that all lab tests are the same or all pharmaceutical drugs are the same. Do you get a shot for epilepsy when you have diabetes? Hardly. There are DNA tests and there are DNA tests. Customers are generally careful to get  the right medicine from a reputable doctor. A customer needs to be just as careful choosing a DNA test and a DNA ancestry company. Not all DNA ancestry companies, even some of the larger companies, have an ISO certified lab, for instance. This not only guarantees the reliability of results, it is also the highest standard in the genomics industry. A few have this laboratory benchmark, but it is, unfortunately, not required, in direct- to-the-consumer DNA testing. Would you want to entrust your genetic identity with anything less? The buyer needs to be aware that with non-certified labs there is a stronger possibility of contamination or lost or swapped samples. I know someone who was the unknown victim of a sample swapped. He thought he was someone else for two years.

Secondly, there are a variety of tests to choose from. There are sex-linked tests (Y chromosome, X chromosome- mitochondrial) and non-sex linked tests called autosomal. The sex-linked tests are haplotype tests based on genetic markers handed down by the male (Y chromosome, received only by other males) or female (mitochondrial). The industry started out with sex-linked testing, but its limitations dictated a move increasingly to autosomal or non-sex linked testing. There are weaknesses with sex-linked tests.

The mitochondrial genome is small compared with the nuclear genome according to the article “Mitochondrial Genome Analysis with Haplotyping” which means there cannot be that much variation with mitochondrial DNA analysis. For instance, some have expressed doubts that the recently found Leicester skeleton could be Richard III because of the mitochondrial DNA analysis that was done. Live Science writer, Stephanie Pappas, quoted Maria Avila, a computational biologist at the Center for GeoGenetics at the [British] Natural History Museum as saying “people could share mitochondrial DNA even if they don’t share a family tree” (Pappas).

How is this possible? Mitochondrial DNA is ancient DNA and mutates slowly.  In the article, “Doubts Remain that the Leicester Body is Richard III,” a Mark Thomas at University College London is quoted as saying that “people can have matching mitochondrial DNA by chance and not be related.” So, it might not be Richard III after all. Male line haplotype testing has different limitations. “The Male Y- linked tests have very rapid mutation rates and are very fragile, so you can get a lot of errors with that type of testing,” according to Dr. Donald N.Yates of DNA Consultants.

According to a recent New Scientist article by Colin Baras, “The Father of All Men Is 340,000 Years Old,” the Y chromosome seems more ancient than previously thought. If so, it is also less stable than we thought. Brian Sykes, Professor of Genetics at Oxford University and the author of The Seven Daughters of Eve, makes a strong argument that the Y chromosome is weakening and in trouble in his book, Adam’s Curse. He says it is “doomed to a slow and humiliating decline” (279) because of its instability and rapid genetic mutation and is thus headed toward extinction. Before the 1990’s paternity testing was based on Y chromosome comparisons and limited to fathers and sons. Sometimes, an uncle would be mistaken as the father. Today, it relies on autosomal DNA comparisons, can be applied to females, and is 99.99% accurate.

But then there are non-sex-linked Autosomal DNA tests which are based on a different science altogether. Anyone can take this traditional type of Autosomal DNA test because it does not rely on X or Y chromosomes (women are unable to take the Male Y- linked test and must entice a male in her line, if one is available, to take this test). This test is not testing ancient DNA but  goes back only some four or five generations, so it does not have these limitations. And it provides a complete analysis of all ancestral lines. Not just one line at a time as in haplotype testing. This is next generation ancestry DNA testing and the wave of the future. Moreover, this type of testing is more stable and has more scientific validity as it uses the same science that is used in the legal court system, by the government, and on CSI comparing loci markers to population databases. And two research teams independently reached the same groundbreaking results that the DNA mutation rate is slower than previously thought:  James X Sun et al., in the article, “A Direct Characterization of Human Mutation Based on Microsatellites,” in Nature Genetics 44/10 (October 2012):1161-65, and A. Kong et al., in the article “Rate of de novoMutations and the importance of Father’s Age to Disease Risk,” in Nature 488 (2012):471-75. All done by the magic of math and laws of large numbers.

What does this mean concerning autosomal DNA ancestry tests? They have even more scientific validity. This second-generation type of DNA ancestry testing is based on these same genetic markers, and that is confirmation that the alleles on your DNA that are examined using a statistical basis have been relatively unchanged for the past 20,000 years. That’s about twice the length of what we call world history, hence a meaningful enough time frame for valid inferences about population patterns and ancestry of individuals. These are markers that everyone has (and why anyone can take an autosomal ancestry test).  These genetic markers change at a much slower rate than the Y chromosome which seems to be highly changeable, depending on the father’s age (Kong 201). (The Y chromosome is a marker only males have. It is used for other types of tests: male, haplotype, sex-linked DNA tests. Only males can take these tests, and it only provides information about that one male line).

Of course, anything can be over-interpreted. DNA testing is not magic. Maybe you should put that crystal ball up after all.


  Comments: 1

  1. Genetic genealogy uses DNA to trace ancestry, while astrology predicts the future based on the alignment of celestial bodies. While they share some similarities, their methods and approach are fundamentally different, with genetic genealogy relying on scientific methods and astrology being a belief system.

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