The Surname is a very important component of a Y-DNA Project, which is one of the reasons that the Projects are called Surname Projects.  The use of the Surname in a Y- DNA Project is to establish a boundary in time for when the persons are related.  For example, when Surnames match and the 25-Marker or 37-Marker results match, then the common ancestor occurred since Surnames were established.

Surnames were established in different parts of the world at different times.  At one point in time, people used just a one part name, or first name.  The use of surnames then evolved, as well as the hereditary nature of surnames (with some notable exceptions).

In England, it was not until the early 12th century that surnames became hereditary among the nobility.  Surnames then spread gradually amongst the ordinary people in the next century, from the town to the country and from the south of England to the north.  Most people in England did not have anything approaching an hereditary surname until the end of the 14th century.

The present day form of many surnames is due to the spelling established in the 16th or 17th century by the clergy.  The present spelling of a surname could even be a result of the spelling recorded by the registrars of births in the 19th century.  There was no guide to the spellings of names, and those who recorded events, such as the clergy and registrars, attempted to reproduce phonetically the sounds they heard.  The great majority of the population were illiterate and had no notion that any one spelling of their name was more 'correct' than any other.  Many surnames have been corrupted to such an extent that their original forms may only be discovered after considerable research. Discovering the original form of your surname will involve tracing your family tree backwards in time, step by step.  

A quick way to identify the many possible variant spellings for your surname is by using the program Surname Suggestion List (SSL) by Matt Combs.  This program is designed to assist you is searching the Internet for your surname variants.  The SSL program is available to download for free with the stipulation that you make a small donation to the developer, if the program was useful to you.  The SSL will create three (3) lists of similar sounding surnames.  The lists are based on how good a sound match the other surnames are to the primary spelling of your surname.

NOTE:  The "Dictionary of American Family Names", by Patrick Hanks, Editor, 2003, by Oxford University Press (ISBN: 0-19-516557-8) is an excellent source to assist you with surnames currently in use in the U.S.  This source lists 72,000 individual surnames and identifies each surname by type (occupational, habitational, patronymic, nickname, etc.), region of origination, explanation, etymology, alternate forms and frequency. 

KNOWLES  NAMES  DEFINED

Names became hereditary later in Scotland and Ireland then in England, and in Wales and Shetland a large proportion of the population did not develop stable hereditary surnames until the 18th century.  Many of the surnames in Wales did not become stable until the middle of the 19th century.

Throughout time, events could occur which changed the surname, such as an informal adoption when a widow remarries.  Occasionally there was a voluntary name change, just as occurs today.

The spelling of a surname could change when a family migrated, due to the pronunciation being interpreted as a different spelling in the new local.

When selecting variants for a Surname Project, the IGI (International Genealogical Index) is a good guide, since the IGI usually has all variant forms of a surname grouped together under a standard spelling.  Many of these forms of the surname do not survive to the current day, either because the male line ended, or the spelling was only recorded for a period of time.  To determine which variant forms survive today, the variants from the IGI can be used to search various on-line phone books or by using the DAFN.

When the surname matches and the Y-DNA result matches (even with a 12-marker test), you have established that the persons are related since the adoption of surnames.

The maximum time frame for the common ancestor would vary based on when surnames were established in the local where the ancestors were located.

When the surname doesn't match, and the Y-DNA result matches, a decision needs to be made as to whether to pursue the match.  The match could be the result of any of the following:

convergence

adoption

extra marital event

related before the adoption of surnames

change of name

Most likely, a matching Y-DNA result with a different surname was caused by either convergence, or being related before the adoption of surnames.

These two situations would normally not be pursued.  For the other situations, a decision must be made.  The odds are small that an adoption or extra marital event occurred.  Before deciding to pursue a match where the surname differs, determine if there is any genealogical evidence that an adoption or extra marital event is a possibility.  For example, was a child born within a few months of a marriage?  Did a widow remarry?   Did people with the other surname reside in the same local at any time?  Is there any evidence of a change of name, such as a census entry for the family with a new name?

Many times, Y-DNA matches with other surnames are not worth pursuing.  If your Haplogroup is R1b, you will usually get a large number of matches with other surnames.

Just as there are surnames with a high frequency of occurrence, such as Smith, Johnson and Jones, and surnames with a low frequency of occurrence, there are both Haplotypes with a high frequency of occurrence, and Haplotypes with a low frequency of occurrence.  The 12-marker result from the Y-chromosome 12-Marker test is called a Haplotype.

When you compare a 12-marker result to another 12-marker result of someone with the SAME surname, and the results match 12/12, there is a 99% probability that you are related.  If you compare a 25-marker result to another 25-marker result for the SAME surname, and the results match 25/25, then there is 99.9% confidence that the two individuals are related.

If you compare the 12-marker result to someone else who does not have the same surname, but the scores match, you are most likely NOT related.  When we use the term related, we are talking about within the last 1,000 years or approximately 40 generations.

According to current theories, we are all related.  The degree of relatedness depends on the time frame, or generations between the participants and the common ancestor.

If two 12-marker results match for two participants with the same surname, and the genealogy research shows a common ancestor in 1835, the DNA test has validated the research and proven that the two descendents are related.  In this example, you have two items of evidence to support that the individuals tested are related. In addition, the research provided a precise time frame for the common ancestor.

Without the genealogy research, and where 2 participants with the same surname match on the 12-marker test, then the scientific answer to the degree of relatedness is that 50% of the time the common ancestor would have occurred within 14.5 generations, or within approximately 360 years.

The range of generations for the common ancestor extends to 76.9, or almost 2,000 years.  These long time frames exhibit the need to combine testing with genealogical research.

The 25-marker test will more accurately determine the time frame of the common ancestor.  If 2 participants with the same surname match 25/25, then the most likely time frame for the common ancestor is reduced to within 7 generations, or most likely within 175 years.  When combining test results with genealogical research, you can achieve a more precise time frame.  If you have a paper trail to a common ancestor, then the test result of a 25/25 match is confirming your research.  If you have the paper trail, and you get a 15/25 match, you either have a problem with the research, an extra-marital event, or an adoption in your family tree.

If you have a rare Haplotype, and you click the FIND selection to search for your matches, the results should all have your surname.  When you have a rare Haplotype and you have a match with a different surname, this is most likely the result of an adoption or extra marital event.

If you do match 12/12 with someone with a different surname, you may want to compare your research to see if you can place any ancestors in the same location at the same time, to begin an investigation of adoption or extra marital event.  Most likely you may also want to expand testing to include other direct male descendents in both your trees for additional evidence to determine when the event occurred.  The preceding advice is only for those with a rare Haplotype.

If you have a high frequency, or common, Haplotype, the FIND command will provide you with many matches to many different surnames.  Even though you match, you are not considered related, in the sense that any relatedness was probably to far in the past to have any genealogical value.  Of course, there is the slim probability that one of the many matches of other surnames is the result of adoption or extra marital event.  The 25-marker results will help identify this person.

It has not been scientifically proven why some Haplotypes are common and others are rare.  Many factors are believed to have influenced the situation over time to produce common and rare Haplotypes.  These factors would include male birth rates, diseases and epidemics focused on localities, migration patterns, mutation rates, etc.  More scientific research is needed to have more specific answers regarding why some Haplotypes are common and some are rare.

It is important to consider whether your Haplotype is common or rare, to effectively interpret results from 12-marker testing.  If your Haplotype is rare, and you have a 12/12 match with a different surname, it might be worth your time to pursue this match, with comparing research and upgrading to the 25-marker test.  If your Haplotype is common, and you match 17 participants with 17 different surnames, you will probably not want to pursue these matches.   How many matches you get to different surnames indicates whether your Haplotype is common or rare.

To more precisely define your degree of relatedness when you have the same surname, and a 12/12 match, consider upgrading to a 25 or 37 marker test.  DNA testing is not meant to be a substitute for genealogical research.  DNA testing combined with your research and your surname is an effective tool to resolve unanswered questions, determine relatedness, identify research problems, and to prove or disprove theories or research.

With a 12-marker test, your degree of relatedness to another whom you match 12/12 involves both the surname and your genealogical research.  If you don't have a documented connection to a common ancestor, and you have a rare surname and a rare Haplotype, you can assume that you are related with a 12/12 match.  This conclusion is not reasonable for common Haplotypes.

For those with common Haplotypes, genealogical research and a 25 or 37 marker upgrade is recommended.  For those with a common Haplotype, a 10/12 and 11/12 match can be deceiving.  They may or may not be related.  In this case, a 25-marker upgrade is recommended to determine the degree of relatedness.

In summary, the following chart applies when combined with genealogical research.  For charts showing less than exact matches, see the DNA-101 Genetic Distance article.