Please note that I am not an expert with regards to this topic and only wish to state what I understand to be true in the hopes that others will consider it when embarking on their own DNA research.
The structure of part of a DNA double helix
Recently, Ancestry has been encouraging large numbers of people to jump on the DNA bandwagon by offering very low prices for genealogically oriented DNA testing.
As with most things related to Ancestry these days, the results of these tests will lead participants to connect with each other in hopes of combining their research efforts. Participants are encouraged to compare “Haplogroups” to point to probable connections.
Only 2 Blood Lines Need Apply
There are only two lines within our family trees that can be illuminated through DNA testing. These are our direct paternal and direct maternal lines. By that I mean my father’s, father’s, father’s, father, etc… and my mother’s, mother’s, mother’s, mother, etc…
A further complication related to DNA testing is that while men can test both patrilineal and matrilineal lines because we have both the X- and Y-chromosomes, woman can only test for their matrilineal line using samples from their own DNA because they do not carry the Y-chromosome of their fathers which contains the information they need. To get around this problem, women may enlist male members of their immediate family to test for their common patrilineal lines. The obvious choice for testing would be a woman’s father, brothers, or paternal grandfather. Other candidates would include a woman’s father’s brothers or father’s brothers’ sons.
But what about the others?
Beyond the two specific blood lines mentioned above, DNA testing reveals nothing. For instance, you cannot learn anything about your father’s mother’s line or your mother’s father’s line. In a standard pedigree chart with ourselves set as the first entry on the far left of the chart, these two lines are usually represented by the very top and very bottom lines extending away from us. All other lines fall outside of the story our DNA carries. No exceptions. It is important to understand this limitation to DNA testing as no matter who does the testing or how, these limitations are standard to all.
The Seven Daughters of Eve
I first became aware of mitochondrial DNA testing reading the book, The Seven Daughter’s of Eve by Brian Sykes, Chairman and Professor of Human Genetics at the University of Oxford.
I would encourage anyone interested in the science behind DNA testing to seek out this book and read it from cover to cover.
Sykes has a unique perspective, as much of what is know and used today in the field of DNA testing is based on and/or is a direct result of his team’s pioneering efforts which are reviewed in detail in the book. To his credit, he takes an extremely complex subject and makes it understandable to the average lay person. Hey, even I got it!
95% of all Europeans can trace their ancestry to just seven women who lived between 10,000 and 45,000 years ago. Sykes has assigned each of these seven women names; Ursula, Xenia, Helena, Velda, Tara, Katrine and Jasmine. These are the seven daughters of Eve.
Since the time of the book’s publication in 2000, much more research has been done and there are now about 36 daughters that have been identified world-wide. Everyone alive today (Over 7 Billion of us) is related to and is a direct descendant of one of these 36 women. The proof lies in every cell of our bodies.
Of course, these women did not exist on the planet alone. Each of them had a mother and a father, but to be the head of a clan, (Sykes also refers to these daughters as Clan Mothers) each of these women had to have at least two daughters. No one before them met this criteria, so these 36 women represent the longest continuous lines of matrilineal DNA that has been carried from generation to generation all the way through to the present. In turn, each of the 36 Clan Mothers can be traced back to their own Clan Mother which is a single woman that Sykes call “Mitochondrial Eve” who lived some 150 to 200,000 years ago in Africa.
Using DNA Testing for Genealogical Research
Genealogical DNA tests generally involve comparing the results of living individuals to historic populations, but how easy is it to compare DNA test results within the context of written history?
My understanding is that DNA testing has limited value in genealogical research, particularly as it relates to mitochondrial DNA which is characterized by mutations that occur only rarely over vast periods of time. While DNA testing is great for reaching far into the past to discover which of the 36 “Clan Mothers” or “Daughters of Eve” we are related to, testing is not so good at examining short term changes that have occurred within recorded history. This means much of the testing for mitochondrial DNA will be of little use for people working within the past several hundred years.
As mutations occur much more frequently in Y-chromosome DNA, there is more value in comparing Y-chromosome DNA with others particularly of the same surname as DNA can prove or disprove what surnames can only suggest. After all, DNA doesn’t lie, but sometimes our ancestors did. As such, genealogically oriented DNA testing works best when comparing results with others who claim the same patrilineal line.
More Markers for Better Results?
To offset the problem of limited changes in the recent history of our DNA, most genealogically oriented DNA testing uses more markers than Sykes Oxford team uses for their “deep ancestry” research. The claim is that this offers better results by examining a larger sequence with the opportunity to discover more variations. Sykes cautions however that increasing the number of markers reduces the acuity of the tests and makes the results harder to draw conclusions from. That’s not to say that there is no value in genealogical DNA testing, but that this type of testing should be viewed with caution as probabilities for errors are much higher when used to examine and compare recent generations.
