DNA Genealogy

I hear a lot about DNA and what it can tell me about my ancestors, so I thought I would check mine out.  I found out that I am a member of the paternal haplogroup T, the “Valley Farmers.”

In recent years, DNA testing has become an important tool in criminal investigations; most commonly used to prove a relationship to an individual.  New tests have also turned DNA into a popular tool for determining ancestry.   Some parts of the DNA remain almost unchanged from one generation to the next, while other parts change greatly.  This link between generations could be of help in reconstructing my family history.

The cost of a DNA test has finally come down to a point where I would consider it.  Several companies provide the service and they offer three main types of tests for genealogical purposes.   By genealogical purposes, I mean that the test will help in reconstructing my ancestry.  These tests will not detect my medical tendencies, physical traits, or personality quirks.  And it can’t be used to convict me of stealing that pencil in the third grade.  It’s not about me; it’s about my ancestors.

The major types of genetic testing for genealogy purposes are autosomal, MtDNA and Y-chromosome.  I don’t pretend to know enough about each to explain all the ins and outs of each, but I think I understand their purpose.   In reading about the tests I found that most scientists call these tests "recreational genetics" or "vanity tests” because they have significant scientific limitations and rely on misconceptions about race and genetics.  So, if this is not serious science, what is the value to me other than feeding my vanity?

Autosomal DNA

Ancestry.com has a test that analyzes autosomal DNA, which includes the entire genome—all 23 pairs of chromosomes at over 700,000 locations. Both women and men can take the new test, and it provides a more complete picture of family history.   The results will be compared with other results in the company’s database to see if I have “genetic cousins”.  It will also tell me something about my combined paternal and maternal lineage over the last few hundred years.  

A problem with this approach, scientists say, is that because such tests analyze less than 1 percent of a person’s genome, they will miss most of my relatives.   The chance that an autosomal DNA test will accurately detect a relative decreases with the distance of the relationship. For example, most autosomal DNA ancestry tests predict an accuracy rate of 90–98% when detecting a match with a 3rd cousin, but around a 45–50% chance of detecting a match with a fourth cousin.  The biggest limitation is that my cousin must be in the company data base to get a match.  

Autosomal results would show me the mix of ethnicity in the previous 2-300 years; after that, due to recombinant DNA the accuracy falls off significantly.   I already know the ethnic mix for the past 300 years so the results would tell me little additionally; and the error rate could mislead me.  As the cost of this analysis continues to decrease, more and more results are being collected.  As the size of the data base grows, the accuracy will increase.  This is a test I will watch and probably use in the future.

MtDNA Testing

Females, as well as males, can discover their ancient maternal lineage through DNA testing. Because a father's mitochondrial DNA (mtDNA) is destroyed at fertilization, a child inherits only the mother's mitochondrial DNA, thus preserving the maternal link to the ancient past. Due to this unique inheritance pattern, both males and females may directly contribute a DNA sample for testing the maternal lineage.

Mitochondrial DNA (or mtDNA ) would trace my maternal ancestry.  Both men and women possess mtDNA, but only women pass it on to their children.  My mother inherited it from her mother, who inherited it from hers, and so on back through time. Therefore, mtDNA traces an unbroken maternal line back through time further back than any written record.   But if I go back 10 generations, the test is telling me something about only of more than a thousand ancestors.

All of our maternal lines connected at some time in the past and these connections can be traced by reading mtDNA.  People tended to cluster into a small number of group defined by their mtDNA.   In native Europeans, for example, there were seven such groups; romantically named Helena, Jasmine, Ursula, Tara, Katrine, Xenia,  and Velda.  An mtDNA result could indicate in which of the seven clans my maternal line originated.   That would be interesting, and I may still pursue it.

Y-DNA Testing

A male providing his Y-chromosome sample also represents the DNA of his father, paternal grandfather, and so on up the paternal line. Y-chromosome results are generally identical throughout the paternal line. But because mutations do occur, it is possible for a son's results to be slightly different from his father's or his brother's.

Y-DNA results would trace my paternal ancestry back for thousands of years.  My primary interest has been in pursuing the Vacek surname.   Y-chromosome results would help me follow the Vacek line back to long before written records were kept.  The result would place me in a haplogroup which could be matched with others around the world.  The Y-DNA test looks at specific regions of the Y-chromosome. These regions are known to contain a series of repeating sequences of DNA molecules.  All men have these repeating segments; what differs between men is the number of times the specific sequence repeats. Counting these repeats is what constitutes the results of the Y-DNA test.   Ancestry.com DNA offers two Y-chromosome tests: Y-DNA 33 or Y-DNA 46 markers (or locations on the Y-chromosome).   Testing more markers allows for a more accurate estimate of the relationship between two individuals.

I submitted the sample for Y-DNA 46 and the results indicated I belong to paternal haplogroup T, the Valley Farmers, which arose at least 30,000 years ago, making it one of the oldest haplogroups found in Eurasia, which may explain its vast dispersal around Africa and South Asia.  It also makes its place of origin uncertain. A low level of phylogenetic resolution has hindered studies of the origin and dispersal of this interesting haplogroup.  The modern distribution of paternal haplogroup T in Europe strongly correlates with the Neolithic colonization of the continent by Middle Eastern farmers.

BUT, while most agree that the haplogroup originated a long time ago, there is only speculation as to where it originated.  Some link it to the ancient Sumerians and Elamites.  Others attribute it to the Phoenicians.  The bottom line is that the Y-DNA test told me that I belong to the paternal haplogroup T and that us T’s are rare in this world; less than 1% in Europe.  We started out as Middle Eastern farmers, moved to become Bohemian farmers, and ended up Nebraska farmers.  

 One of our Haplogroup T brethren is Thomas Jefferson.  Jefferson was a passionate farmer, as well as architect, inventor, and statesman.  And like most farmers, he died broke, but happy. In 1781, Jefferson wrote in his Notes on the State of Virginia, "Those who labour in the earth are the chosen people of God, if ever he had a chosen people, whose breasts he has made his peculiar deposit for substantial and genuine virtue. It is the focus in which he keeps alive that sacred fire, which otherwise might escape from the face of the earth."

 

Although haplogroup T is more common today in East Africa than anywhere else, its association with the rise of agriculture in the Middle East is a strong argument in favor of a Middle Eastern origin, and a colonization of East Africa by Middle Eastern farmers.  The strong incidence of T from the Caucasus to central and southern Iran hint that early farmers might have descended from the Caucasus to southern Mesopotamia and southwest Iran. 

Distribution of paternal haplogroup T in Europe, the Middle East and North Africa

T is a rare haplogroup in Europe and patchy or regionalized.   It makes up 1% of the population on most of the continent.  In the Czech Republic where the Haplogroup R1 accounts for over 50% of the population, haplogroup T accounts for only 1%.   A small study in Vysocina shows a T population of 2.5%; another in Plzen of 1.6%.