Y-Chromosome DNA Analysis:
Genetic Genealogy and Male Ancestors

Have you ever thought about having your Y-chromosome DNA tested? Perhaps you were adopted, and wonder who your biological family is. Maybe you would like to know (as I would) who was the father of one of your ancestors. Or you’d like to know what ethnic groups your male ancestors were from.

Many of these questions can be answered, in terms of the male line, by Y-chromosome DNA analysis.

Since females do not have a Y chromosome, a male relative who is a direct descendant of the male in question would have to take the test for her.

For Y-chromosome DNA, there are two types of tests: STR (short tandem repeat) tests, and SNP (single nucleotide polymorphism) tests.

STR Y-Chromosome DNA Tests

DNA molecule.
Photo courtesy of Flicker
via Wikipedia.
DNA molecule

Scientists have discovered that Y chromosomes are passed from father to son virtually unchanged. Over time, there may be slight changes, or “mutations”, which occur during replication of cell DNA, but the majority of Y-chromosome DNA remains the same. When a mutation does occur, all male descendants of the man carrying the changed Y-chromosome DNA will have that mutation. When a second mutation occurs, all of that man’s descendants will carry that mutation as well as the first one, and will be a distinct sub-group of the group with the first mutation. Essentially, these represent "branches" on the human Y-chromosome DNA tree.

Geneticists have developed ways of measuring the likelihood that the nearest common ancestor was a certain number of generations away in the family tree, depending on the number of mutations in the Y-chromosome DNA. Therefore, if two men are tested and their Y-chromosome DNA is virtually identical, the conclusion is that they share a common ancestor. The more closely they match, the nearer the common ancestor was. Hence, the more markers are tested, the more accurate the results are, and the more likely it is that an ancestral link between two individuals can be related to a particular time period or number of generations in the past.

This test is called an STR (short tandem repeat) test, which looks at the number of repeats of a particular strand of Y-chromosome DNA at various markers. It provides a person with their personal haplotype (the chart of the number of STRs at each marker tested). When combined with a comparison of family trees between tested individuals, this can be a powerful tool for a genealogist.

The following video illustrates how one man used this test to find his birth parents.

For a more in-depth look at DNA and its application to family history, see DNA Testing Adviser.

It seems there is a sequel to Richard's story. Through further testing and investigation, he has learned that a different male member of his paternal family was his biological father. Richard has written a book about his journey to find his biological parents, which is advertised on the DNA Testing Adviser website.

Add a story about the results of a Y-chromosome DNA study - perhaps your own?

Thomas Jefferson: Using DNA Testing on a 200-year-old Controversy

The uses, and limitations, of this type of testing are further illustrated in the case of Thomas Jefferson, 3rd President of the US. Beginning in 1802, rumours appeared in the press that Jefferson, following the death of his wife in 1782 (who extracted a promise from him on her deathbed that he would never marry again), had fathered some, if not all, of the six children of Sally Hemings, a slave in his household. In the America of that day, it was illegal for such a relationship to exist, and it would have been regarded as scandalous. Jefferson, who had a policy of never responding to personal attacks, made no comment one way or the other.

The rumours have persisted, even to the present day. Many of Sally Hemings’ children claimed descent from Jefferson; one went so far as to change his name from Eston Hemings to Eston Hemings Jefferson in 1852.

Portrait of Thomas Jefferson, 1800
Public Domain
Thomas Jefferson painting

Naturally, Jefferson’s family (his immediate family consisted of six children, among whom only two daughters lived to adulthood) denied the allegations. Some claimed that Jefferson’s nephews, Peter and Samuel Carr, had fathered Sally’s children, which, according to them, accounted for the light-skinned children’s resemblance to Jefferson. However, two of Sally’s children explicitly stated that they were Jefferson’s children, and this belief was passed down through the generations of descendants.

I’m sure that Thomas Jefferson thought that he would take whatever secrets he may have had with him to the grave.

Enter DNA testing, in 1998, approximately 200 years later. At that time, a team of geneticists led by Dr. Eugene Foster did a Y-chromosome DNA study intended to set the persistent rumours to rest one way or the other. Since Thomas Jefferson and his wife had no male offspring, they used DNA from male descendants of Field Jefferson (Thomas Jefferson’s uncle), John Carr (grandfather of Peter and Samuel Carr), Eston Hemings, and Thomas C. Woodson (Sally Heming’s first-born son).

The results of the study showed no genetic link / relationship between male descendants of John Carr and the Hemings descendants, although Thomas Woodson’s male descendants had a Y-chromosome which closely resembled that of the Carr male descendants. Neither was there a relationship between Field Jefferson and Thomas Woodson.

It did, however, establish that a carrier of the Jefferson Y-chromosome had fathered Eston Hemings (born in 1808), the youngest of Sally’s children. The problem, of course, was that there were about 8 male Jeffersons living in the area at the time that Sally’s children were conceived, a few of whom had visited Monticello, the plantation which Thomas Jefferson owned and where Sally Hemings was a slave.

After reviewing all of the surrounding circumstances and evidence, the study’s authors concluded that, while it was possible that other Jefferson relatives were responsible, the simplest and most probable conclusion was that Thomas Jefferson had fathered Eston Hemings.

Monticello, Jefferson's home.
Source: C. Hollis for Wdwic Pictures
on Wikipedia Commons


The Thomas Jefferson Foundation formed a research committee, which reviewed all of the available evidence which the Foster study had used, and concluded in its report dated November 1998 that Thomas Jefferson most likely had fathered Eston Hemings, and that it was possible that he had fathered all six of Sally Heming’s children.

The Thomas Jefferson Heritage Society then commissioned a group to review essentially the same materials, and in 2001, they reached a different conclusion: that it was very unlikely that Thomas Jefferson had fathered any of Sally Hemings’ children, and that it was more likely that his brother, Randolph Jefferson, was the father of some of her children.

The debate therefore continues. While some continue to state that Thomas Jefferson was not the father of Sally Hemings' children, most have come to accept that this is most likely the case.  It is noteworthy that Thomas Jefferson freed all of Sally Hemings’ children and a few of her brothers, some prior to his death, and some under the terms of his will - the only slave family unit which was freed.

Sally herself was not freed, but not long after his death, Jefferson’s daughter allowed her to leave Monticello. She went to live with two of her sons.

This example clearly illustrates the limitations of the Y-chromosome STP test. While it can narrow down the possible common ancestors to a fairly small group who carried the same DNA markers, it is not possible to state definitively, based on the DNA evidence alone, which of the men in that small group was the father. Nevertheless, the DNA evidence, combined with the circumstantial evidence surrounding the case, certainly points to Thomas Jefferson or a very close relative of his as the father of Eston Hemmings.

Niall of the Nine Hostages, 4th Century Irish Warlord

Another recent study, this one from Trinity College in Dublin, Ireland, tested the Y-chromosomes of a number of men in Ireland and Scotland. It was discovered that a large number of men in these two areas had the same Y chromosome.

The study indicated that the Y-chromosome appeared to trace back to one person. The researchers looked at a number of surnames that came from that area, and tested the Y-chromosomes of those family members to see whether there was any genetic connection between those families and the genetic profile. They concluded that all of those tested with those surnames were descendants of the same man.

To the researchers, this suggested that “Niall of the Nine Hostages”, a 5th-century warlord who died about 405 A.D., and whose descendants were "kings" in various areas all over Ireland and in parts of Scotland, could be the ancestor of as many as one in every 12 Irish men.

Niall and his descendants, powerful chieftains, dominated Ireland for six centuries. In the northwest area around Ulster that was their “powerbase”, 21.5% of men were found to carry the same Y-chromosome, and 98% were in haplogroup R1b, compared to 90% in southeast Ireland.

Astounding results, dating back about 1600 years!

Y-Chromosome SNP Testing

SNP testing looks at mutations in the Y-chromosome. Males who share a specific mutation all belong to a particular branch, or haplogroup, of the male population, and are descended from a common male ancestor.

Y-chromosome STR results provide the personal haplotype, while Y-SNP results provide the haplogroup. Although Y-STR results can point toward what an individual’s haplogroup might be, the haplogroup can only be confirmed by a Y-SNP test.

Where is Y-Chromosome DNA Testing available, and at what cost?

Y-chromosome DNA testing is widely available throughout North America. One US company has placed its kits in drug stores throughout the US; most, however, send out a kit to the address provided when an order is placed, with instructions on how to use it. Kits can be ordered over the internet, or by telephone. Many US-based companies also provide their services to Canadians, although I did find a few companies operating in Canada, as well. Where companies do surname projects, prices tend to be discounted if you are joining a surname group.

Each company appears to offer its services a little differently. For example, one company offers a Y-string 44-marker test for $109, and a Y-SNP test for $130, while others offer a test which appears to be a combination of the two for a slightly lower price than those two done separately. Others offer a “Y-string” test, but do not specify the number of markers tested. As potential customers, we therefore would be wise to ask lots of questions as to what is included in the price before deciding which company to use. Prices appear to range between US$109 and US$268, depending on the number of markers tested and what is included in the analysis.

For companies operating in Canada, prices range between C$119 for 12 markers and C$229 for 44 markers. It is unclear whether these prices include an SNP test as well, with migration information and haplogroups.

For a listing of the big players in the field, and a comparison of their y-DNA products and pricing (as of 2008, unfortunately), click here. While some of the information may be somewhat dated, it gives a general idea of who the main companies are, and the types of y-DNA services offered.

The prices listed are not meant to be an exhaustive list of the price ranges available in both countries. It is likely that there are higher- and lower-priced kits available from other suppliers, depending on what is included in the package. The prices shown are meant to serve only as guidelines. Further, prices keep changing as competition grows, and as researchers expand the possibilities with new discoveries in the genetic area, resulting in newer, more sophisticated tests being offered.

As of 2017, while there may be other players still in the field, the 'main player' in this field, for genealogists, at least, is Family Tree DNA.

Go from "Y-Chromosome DNA Testing: Genetic Genealogy and Male Ancestors" to "mtDNA Testing: Genetic Genealogy and Maternal Ancestors"

Go to "DNA Testing: Tracing Family Trees with Family Finder and Relative Finder Tests"

Go to "Genetic Genealogy: DNA Testing applied to Family History"

Go to "Surname Projects: Genetic Genealogy and Shared Surnames"

Go to familyhistoryalive Home Page

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