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About Y-DNA

(And how we use it in Taylor Family Genes)

We focus primarily on Y-chromosome DNA because it is  most strongly associated with surnames, including Taylor. Other DNA types are associated, either with maternal ancestry or all ancestry, in which many surnames are involved. Y-DNA has become a powerful genealogical tool to identify male ancestors in common with others. It is a valuable supplement to traditional documentary genealogy; it is not a substitute for it.

The typical test for genealogical purposes is the STR ("short tandem repeats") of allele values for 12 to 111 "markers" (loci or microsatellites). SNP (single nucleotide polymorphism) tests are available for deep ancestry and other purposes.

Note: We formerly used the acronym "Y-DNA". However, the more acceptable form is "yDNA" and we're converting to it.

Other Resources

Read this excellent DNA 101 by John Blair for an in-depth discussion of the science. Also, Dr. Bruce Walsh's explanation of the math.

Types of yDNA Tests

There are two types of yDNA tests:

  1. ySTR

    is the more common test. Unless specified, we usually mean ySTR tests. These tests, of short tandem repeats for 12 to 111 or more markers, count the number of times a particular DNA sequence (e.g., CCTG) is repeated at a position on the Y chromosome. The resulting string of marker names and their values yields a quantitative description of the haplotype. When two or more haplotypes are sufficiently similar, they are said to "match".
  2. ySNP

    is rapidly gaining in popularity. These tests, of single nucleotide polymorphisms, look for mutations (e.g., from A to C) of a nucleotide at a specific chromosome position. SNPs definitively establish haplogroups on the Y phylogenetic tree and, in some instances, "zero in" on specific genetic families (patrilines) within genealogic time.

These two types of tests work very differently from each other. A ySTR test always requires comparison against other, similar tests. A ySNP test is compared against (usually) populations' results.


Purpose and Performance of Y Tests

yDNA tracks a direct biological paternal lineage; the purpose is to identify that lineage by genetic matches with living men who share it.

When such matches are found, Y-DNA is fairly reliable; it identifies the specific lineage with reasonable certainty and excludes other lineages with greater certainty.

When matches are not found, it is because either:

  1. The database searched does not contain a sufficiently similar haplotype. Possible solutions:
    1. Search in databases which contain results from multiple providers, e.g., Ysearch.
    2. Purchase a test from a company with a more inclusive database, e.g., FTDNA. (There are none at present.)
  2. The search has been too restrictive; potential matches have been ruled out.
    1. Remove restrictions such as surname.

Why Test?

Reasons to test yDNA for genealogy include:

  1. Overcome "brick walls": If your genealogical research is stymied, Y-DNA may produce a break-through. "Your Y-DNA may help you find genetic cousins along your direct paternal line."
  2. Focus traditional documentary research as to time and place: Knowing that your cousins' ancestors were in particular places at particular times aids in the search for relevant records for your own lineage.
  3. Answer "Am I really a Taylor?": A Y-DNA match with other Taylors answers yes. Matches with another surname predominating answers in the negative.
  4. Identify which specific Taylor family is yours: There are many Taylor families and not all are related, except in belonging to the human race. Y-DNA tests are good at sorting out genetic families.
  5. Illuminate "deep" ancestry: Haplogroups relate to ancient tribes, clans, cultures and immigrations. DNA sheds light on prehistoric mysteries.
  6. Refute a genealogical claim: If two men do not share a direct paternal ancestor, their Y-DNA haplotypes are highly unlikely to be similar. The dissimilarity will prove the absence of a common direct paternal ancestor within genealogic time.

The Concept

All males -- and only males -- have a Y chromosome; the dioxy-ribonucleic acid (DNA) in the Y chromosome is called Y-DNA. It is passed down, from fathers to their sons, with little change for many generations. (See our page on Y-haplotype stability.)

Comparing the Y-DNA haplotypes of two males can say whether they share a common male ancestor, abbreviated CMA, and yield a probability estimate for the number of generations to the CMA. In general, the more similar the haplotypes are, the more likely and more recent the common ancestor.

Comparing the Y-DNA of one man to a database of samples collected from throughout the world can shed some light on the ethnic & geographic origins of very distant paternal ancestors.

However, Y-DNA follows only the direct & unbroken paternal line. It says nothing about female ancestors. Picture a pedigree chart, where fathers are represented above mothers: Y-DNA traces the top line of the chart.

Y Chromosome Facts

The Y chromosome is passed exclusively through male sperm. 95% of it is incapable of recombination with its paired X chromosome in meiosis; only the tips can recombine. This is in stark contrast to chromosomes 1-22, which recombine with their counterparts from the other parent.

The Y was discovered in 1905 by a woman, Nettie Stevens, Ph.D. (1861-1912) at Bryn Mawr College; that same year, Edmund Beecher Wilson (1856-1939) discovered it independently. Dr. Stevens also was the first to hypothesize that the Y paired with the X (discovered 15 years earlier) and its role in determining gender.

The Y is a lean, mean fighting machine -- stripped down to essentials. It is the smallest among the 46 (23 pairs of) human nuclear DNA chromosomes and shows the least variation. It contains only 27 genes and 50 million base pairs, whereas other chromosomes contain thousands of genes and 51 to 249 million base pairs. Only the (non-nuclear) mitochondrial genome, at 16,569 base pairs, is smaller.

Humans share 17 of these genes with other mammals, but have added another 10. Over 200 million years of evolution, about 1400 genes have been deleted from the Y, probably in a "weeding-out" process.

It is specifically the SRY gene on the Y which triggers development as a male. If this gene crosses over to the X chromosome, a rare "XX male syndrome" can result.

In about one per 1,000 male births, a boy may receive more than one Y chromosome, the "XYY syndrome", resulting in 47 chromosomes. Such boys are usually taller than average.

The Test

The testing process is user-friendly. Swab the inside of your cheek with a brush (or Q-tip) provided by the testing company to get a sample; this collects skin cells. Place the swab brush in the sterile container provided and mail it back to the testing company's laboratory in the mailing container also provided.

In a few weeks, the laboratory will have done its highly-technical thing, analyzed the yDNA & notified you of the results. These results are the pattern of STR (short-tandem repeats) markers, also known as "loci" or "microsatellites".

Can women test?

Women do not have a Y-chromosome, but they have fathers, brothers and uncles who do. A woman can purchase a kit and collect a sample from one of the men, then submit it under her name. When DNA submitted is not the "kit owner's", it will represent the sample donor, not necessarily the owner.

How much Test?

Members & prospective members often ask us how many markers members should order tested. Cost is a consideration, because panels with more STR markers cost more than those with fewer.

Levels of testing available

Each level of resolution listed below also includes the levels above it. The 37-marker test includes markers 1-12 and 13-25, as well as 26-37.

Y testing levels

Value of More Markers

An administrator of another project had her husband and his father take Y-DNA tests. They matched on 110 of 111 markers, an extremely close match and about what we'd expect for a father/son pair. But the one mismatching marker was found in the first panel of 12 markers. Had they stopped at 12, they might have concluded they weren't really related.

What is the recommended minimum?

Think of the test as yielding a description of your haplotype, which is then compared with others' haplotypes to see how similar they are. The more markers you've tested, the more complete the description. As an analogy, think of describing a man by height and weight, then adding eye and hair color, then adding other details; the more details, the better to identify that man.

We recommend 37 Y-DNA markers as the usual minimum to order and regard it as the standard test. For us Taylors, the lowest-cost 12-marker panel is, more often than not, false economy because an upgrade (at more cost) will usually be needed to "rule in" a common paternal ancestor. An exact 12/12 match contains insufficient information for confident interpretation.

12 markers not recommended

The 12-marker test is an incomplete description which will elicit many "false positives" -- others who match on the 12 tested, but would not match if more markers could be compared; it does not contain enough genetic information. We recommend the 37-marker test or higher for the Taylor surname. There are exceptions to this general rule:

25 markers not recommended

The 25 marker test has been discontinued by FTDNA as an initial offering. However, some Taylor Family Genes members have tested only to the 25-merker level; we recommend that they upgrade to 37 or more makers.

We have low confidence in 25-marker comparisons, both for establishing a match or ruling one out. In general, an exact 25-marker match will also yield a high-quality 37+ marker match, but 1:25 and 2:25 matches show divergent tendencies at the higher levels. They are almost as likely to prove false as to be confirmed.

37 markers recommended

The 37 marker test is the minimum we recommend for paternal genealogy. It is our standard test for the project and includes a panel of thirty-seven Y-chromosome short tandem repeat (STR) markers, balanced between volatile and stable. The additional markers from 26-37 refine the predicted time period in which two individuals are related and eliminate unrelated matches. A perfect match at thirty-seven markers (37/37) indicates the two individuals share common ancestry in recent times.

(This is not only because of the number of additional markers. It is because these 12 are among the most volatile of any markers tested. They discriminate better.) 

The project does not -- except in unusual circumstances -- use less than 37-marker comparisons to conclude that two or more individuals share a paternal ancestor within genealogic time. Fewer markers do not usually give us the confidence to put our credibility on the line.

67 markers recommended

The 67-marker further refines and adds confidence to the time/probability window as to the most recent common ancestor.

111 markers recommended

A recently-available 111 marker test can be helpful in two ways:

  1. For those with common haplotypes, it can reduce the number of matches to a reasonable number for follow-up; (Also see SNP Tests below.)
  2. For those sharing high-quality matches, it is an assist in triangulation and identifying specific branches of a genetic family. (A minimum of four matches at 111 markers is normally required.)

The FTDNA TiP tool may be helpful in choosing which of your matches deserve priority. (The orange TiP icon shows beside the name of each match.) Use TiP to calculate the cumulative probabilities at each generation for the most recent common ancestor. Record the generations numbers where the probability reaches 90% (or some other percent). Those with the lowest generation numbers are more recently related to you. Or, record the 8-generation probability; those with the highest numbers are more likely related. See our page on TiP.

What do I get?

You will receive several services and pieces of information from your test.

  1. The ability to log onto your personal My FTDNA pages at Family Tree DNA.
  2. A description of your Y-chromosome haplotype, which will look something like this example
      13   23   14   10  11-14   12   12   11   13   13   28   ...
    The number of markers listed will depend on your order and the STR values will probably be different.
  3. A prediction of your haplogroup.
    1. If FTDNA is unable to predict a haplogroup from your STR values, you may ask for a free backbone SNP test for a determination. Request it by using the feedback form here.
  4. Excellent after-market customer service.
  5. The ability to search the FTDNA database for close matches to you, including those with your surname.
  6. Access to FTDNA tools and information for interpreting your matches, including TiP -- the most sophisticated TMRCA calculator available.
  7. The services of a DNA project to help you through the process.

Many testing companies provide only two or two and one-half of the above services.

Do these results identify me?

No. The results can not be used to uniquely identify a person. Similar patterns (haplotypes) will be shared with every other member of your paternal genetic family, who could number into the hundreds.

Transferring results from other companies

If you have tested with another company, it may be possible to transfer those results to FTDNA and make them compatible with others in the database. Write to one of the project administrators for more information.

Be aware that other companies test differently than FTDNA and they count markers differently. A 46-marker test from SMGF is not fully comparable to a 37-marker test from FTDNA.

If you transfer your results, we strongly recommend that you, at the same time, order the upgrade to 37 markers and possibly 67.

SNP Tests - Haplogroups & Subclades

The STR tests described above will include a prediction of your Y-chromosome haplogroup as an added benefit. To confirm the prediction and refine your classification, you may also purchase SNP tests. These will enable you to place yourself on the Y-chromosome phylogenetic tree and learn more about your deep ancestry. SNP test results also have a benefit in helping to confirm STR matches.

Y-SNP testing is undergoing a technological revolution; it is rapidly becoming cheaper and more effective. Whereas it was previously of mostly anthropological interest, it's now also helpful (in conjunction with STR testing) in some genetic genealogy uses.

For certain, very common haplotypes, STR testing alone may produce "false positives" due to homoplasty. For example, STR matches may show between men of different subclades of a haplogroup; but -- due to subclade differences -- the men could not share a common direct paternal ancestor for thousands of years. Such matches can be indentified and eliminated through SNP testing.

Big Y and other NGS tests

Next Generation Sequencing (NGS) is the "gold standard" of ySNP testing. Big Y (from FTDNA) and Eleite (from YSEQ) test millions of positions on the Y chromosome for SNPs.

"The Big Y", for $595 (or less), tests 10 million base pairs, including 25,000+ known SNPs. Although such a comprehensive test undoubtedly has genetic genealogy benefits, it's being advertised as an "adventure of personal discovery" and a contribution to science. It's beginning to show promise for genetic genealogy applications.

Big Y -- and other "Next Generation Sequencing" (NGS) offerings from companies have led to many important SNPs transitioning from unknown to demarking branches of the Y tree. .

Similar, and preferred by some experts, is the "Elite" test from Full Genomes Corp. We make no recommendation here, as we believe NGS testing is largely an individual matter.

Deep Clade, & SNP Packs

"Deep Clade" was the name of a bundle of ySNP tests once offered by FTDNA. It was discontinued when emerging scientific knowledge showed that some of the SNPs tested were less relevant than others untested. FTDNA has brought back new and improved versions called "SNP Packs" or "Backbone Panels".

The project's opinion is that Deep Clade test results -- state of the art in their time -- are now, mostly, obsolete. We recommend that these be updated with the SNP Packs or Big Y described below.

SNP Packs & Backbone Panels are bundles of 100 or more SNP tests at prices in the $100 to $120 range; each SNP tested costs about $1. They are difficult to generalize upon because each bundle is customized to a particular haplogroup or subclade. FTDNA is now rolling out these products one at a time as it designs them.

Geno 2.0

Geno 2.0 is the National Geographic Society's second venture into population genetic studies; the first covered 12 Y-STR markers. Its primary purpose is "mapping the pattern of human genetics" -- including SNPs from autosomal DNA, X-DNA, Y-DNA and mtDNA.

While Geno 2.0  (a nickel under $200) covers mostly autosomal chromosomes, "just over 12,000 Y-DNA SNPs" are also included. Of these, about 2,000 have previously been published and are on the Y-phylogenetic tree.


See the ISOGG test comparison chart.

Benefits of a Project

FTDNA -- more so than other genetic genealogy providers -- sponsors surname, geographical and other types of projects for customers' benefit. These projects have advantages for members who join them, including:

The Taylor Surname Project

Our project, Taylor Family Genes, is for the Taylor surname and variations of it. The project provides an unusually wide range of services to its members.

The Results

You'll receive a certificate of the results and a report describing the testing process. (It can be printed from your myFTDNA pages,) For STR testing (the most commonly used), the certificate will have a list of Y-chromosome marker names and each marker's corresponding allele value.

"Marker" (see the glossary) is a term with different meanings in DNA. Here, we use it to mean a STR locus or microsatellite on the Y-Chromosome.

How long is that list of markers & values depends on the level of test (resolution) you paid for. We recommend at least 37 markers for reasons above. The list describes your haplotype.

But, the results mean nothing in isolation from others' results; they must be compared to something to draw any conclusions. We call that process of comparison and drawing conclusions "interpretation".

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The goal of ySTR testing is to find a close match which indicates a common ancestor within the genealogical time frame, i.e., less than 800 years ago.

What is a "match"?

A "match" exists when two (or more) men's ySTR haplotypes are sufficiently similar; they agree enough on the STR value counts for the markers tested in common to indicate, with high probability, that they share a common paternal ancestor. The quality of matches is described in any of these ways:

Basic principle: In general, the more markers that agree and the lower the genetic distance, the more likely it is that two men share a common paternal ancestor and the more likely that this ancestor is more recent. We interpret matches by the probability of multiple independent events.

Visual Representation

It may help to show pictures. Here is a visual representation of a Y-STR haplotype; let's call it Al's. Each colored bar represents a marker and the height of the bar depicts its allele value.

Now we'll look at two haplotypes together; let's call the other one Bob's. That's the diagram on the left.

To make it clearer, we'll overlay Bob's haplotype on top of Al's and offset them a little, as in the diagram to the right.

All the markers agree and line up, except for the orange marker. For it, Bob's value is less than Al's.

For simplicity, we've drawn only 12 markers. In practice, we use 37 or more markers and do this with mathematics instead of pictures.

What is Genetic Distance?

Genetic distance (abbreviated "GD") is complicated to explain, partly because there are different definitions. Start with the concept that most markers are thought to mutate only one allele (step) at a time. So for most markers, genetic distance is simply the sum of the absolute differences between the markers compared.

Genetic Distance Illustration
Name DYS
Al 13 22 14 10 12 14 11 14 11 12 11 27
Bob 13 22 14 10 12 14 11 14 10 12 11 29
0 0 0 0 0 0 0 0 1 0 0 2 3

Note that, in this simplified illustration,  Al and Bob match on 10 of the 12 markers; they have a difference of 1 on DYS439 and a difference of 2 on DYS389ii, which follows the stepwise model. The total genetic distance between them is 3, for a 3:12 match.

Genetic distance is a crude representation of the similarity, or dissimilarity, between haplotypes. It does not account for varying mutation rates for different markers.

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Types of Matches

Two types of matches are of interest to us:

Reported close matches

FTDNA selects only certain matches to report, based on the number of markers compared and the total genetic distance; it will not report matches for which genetic distance exceeds its thresholds. The FTDNA reporting thresholds are:

In our experience, these reporting thresholds include 90% or more of genealogically significant matches. There are, however, exceptions; some possibly significant matches may not be reported (i.e., "false negative") and some reported matches may not be significant (i.e.,"false positive"):

Significant matches

Knowing you may share an ancestor with another person is not of much value unless that ancestor can be identified by name, dates, places and other characteristics -- all the stuff that's expected of genealogy. Therefore, we describe the best quality of reported matches as genealogically significant.

Exact Matches

An exact match (where all markers agree and genetic distance is zero) is a special case of a close match. Exact matches across 12 markers are not considered significant because they may be coincidental. But exact matches may be significant for 25 markers and are (with the conflicting-haplogroup exception) significant for 37 or or more. An exact match at 37 or  more markers usually indicates a recent common ancestor, within a few generations.

Project Criteria for Genealogical Significance

The overall criterion for declaring a genealogically significant match within Taylor Family Genes is this:

Y-DNA indicates a high probability of sharing a common male ancestor who lived since 1350 AD*.

* The year 1350 AD represents the usual earliest beginning of the Genealogic Time Frame. It represents roughly 24 generations before present.

This plain-English statement relates the DNA evidence to genealogy and is then translated into quantitative criteria, based either on the number of markers compared and the number which agree (or the genetic distance) or TiP:

Simple Genetic Distance

Genetic distance is only a rough measure of match quality because markers vary widely in mutation propensities. However, this is a general guide:

Genetic distance has undergone several changes in definition over the years. It is presently more complex than a simple sum of allele differences. See this page.


Due to variations in mutation behavior between markers, simple genetic distance is a less precise indicator of genealogical significance than FTDNA's TiP (Time Predictor) algorithm. TiP takes the different marker mutation frequencies into account in calculating a cumulative probability for a most recent common paternal ancestor (MRCMA) existing in a specific number of generations. Our TiP criteria is


These criteria are more restrictive than those used by FTDNA to report matches within its total database, nor are they dependent on surnames matching. Also note that they are more restrictive than past project criteria; some older groups were formed under looser criteria but have not been "revoked". We encourage those with 12- and 25-marker matches to upgrade their testing levels in order to benefit  from the higher precision of the 37-marker and 67-marker tests.

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When another person shows identical or close results within the FTDNA database and if both parties have signed the Family Tree DNA Release, then FTDNA will inform both members of the match. If the match is for 25 or more markers,  your e-mail message will look something like this:

From: info@familytreedna.com
Sent: Tuesday, April 13, 2010 5:53 PM
To: member@domain..net
Subject: Family Tree DNA Kit# 999999 Y-DNA25 Test Match

A 25 marker match has been found between you and another person in the Family Tree DNA database!

You and the other person(s) have matched in 23, 24 or 25 loci. If you share the same surname or variant, this means that there is a 99% likelihood that you share a common ancestor in a genealogical time frame. If you match another person without the same surname or variant, you still probably share a common ancestor, but this ancestor may have lived in the time before surnames were adopted.

The link below will take you to your Family Tree DNA Login. From there you can see a list of your matches. Newer matches will be at the top of the list. Additional emails will be sent to you as we find new matches between you and your "genetic cousins."

Follow the link below and type in your Kit Number and Password to access your personal page

Your Kit Number is 999999
Your Password is X9999

If you have not done so, please remember to add your results to Ysearch.org, the FTDNA-sponsored public database. Click on the Y-DNA Matches tab to see an explanation and a link for the upload.

Family Tree DNA
The world's first and largest Genetic Genealogy organization

This message was processed by the FTDNA Email System.
The original headers are:
To: member@domain..net
GUID: a6a405c5-48de-4845-8026-14c4fa27143e @ 5.182

If you are a Taylor Family Genes member, the TFG administrator will get a notice looking like this:

From: info@familytreedna.com
Sent: Thursday, April 08, 2010 7:01 PM
To: admin@domain.net
Subject: Taylor Project Member has a Family Tree DNA Y-DNA25 Match

A Y-DNA25 match has been found between Kit 999999, Firstname Middlename Surname, a member of your FTDNA Group Taylor, and another person(s) in the Family Tree DNA database. He and the other person(s) have matched in 23, 24 or 25 loci, which means there is a 99% likelihood they share a common ancestor.

Please direct your member to the link "Understanding your results" at your personal page, where he will find an explanation about the significance of matches. Also, please remind him to add his results to www.Ysearch.org, the FTDNA sponsored public database. When going to the Y-DNA Matches tab and he will see an explanation and a link for the upload.

Follow the link below to access your Family Tree DNA Group Administrator's page.
Your Kit Number is {Admin #}

"History Unearthed Daily"

This message was processed by the FTDNA Email System.
The original headers are:
To: admin@domain.net
GUID: b59970e3-e818-4556-be60-59f64af6616e @ 5.182

You may notice that neither message identifies the party to whom you match. For that information, you need to log into your personal page at Family Tree DNA. Input your kit # and password (both in your message) and when you reach "My FTDNA", click any of the "Y-DNA Matches" links. The website will generate a list of matches according to the specifications you've set. (You may have chosen not to see 12-marker matches or matches outside the Taylor surname. We recommend the first, but not the second.)

The project administration team may send you a follow-up to the FTDNA notice. It will describe the match and its genealogical significance. It may recommend action you can take to improve the meaning.

Can I improve my chances for finding a match?

Yes. You should post your results to a free, open & searchable Y-DNA database such as Ysearch and Ybase. Ysearch, with 70,000 haplotypes in its database,  is sponsored by FTDNA, but accepts results from all testing companies. Ybase, with 15,300 haplotypes, is sponsored by DNA Heritage and also accepts all results..

We've published a Ysearch page on this site to help people upload to it and use it.

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Intra-project vs. Extra-project Matches

Your match may or may not be a member of the project. If two or more project members have a significant match, we'll assign them to a "genetic family", for a common paternal ancestor. There is more about this on our Groups page.

Most project members have at least some matches with persons outside the project. If your match is with a person who is not a project member, we can not assign them (or you) to a Taylor genetic family.

Surname match vs. surname non-match

Some people find that they have matches with surnames other than their own. How to interpret this situation depends on whether:

  1. Most of the surnames listed as yDNA matches are the same or variations of it. Often, the predominant surname is the ancestral one for this haplotype and the others represent NPE.
  2. There are several groupings of similar surnames, especially of Scots or Irish origin. This may indicate an ancestral clan membership.
  3. There are very many matches and no clear pattern to the names. This may indicate  convergence of haplotypes toward similar forms.

I have no matches. Is my DNA rare?

About 8% of our project's members have no matches reported. The answer to "rare DNA?" is yes  much less often than the question comes up. See our page on this subject here. Also, before coming to that conclusion:

  1. Make sure you're comparing against the >500,000 in the FTDNA database and not just the ~750 in the Taylor project.
  2. Make sure you're not looking only for your own surname. More than half of Taylor project members have matches with other surnames; some are highly significant. See our page on NPE.
  3. Consider your haplogroup. Some haplogroups are not well-represented in the FTDNA database because they're not common in the United Sates, where most FTDNA customers reside or the groups with them are less likely to test DNA.
  4. Look for a "null value" (i.e., = zero or blank) in your results; these tend to confuse the match-reporting system.
  5. If your haplogroup is R1b, look to see if you have a "WAMH" or "Niall" designation for your haplotype. If so, at least the first 12 markers of your haplotype are among the most common found.
  6. If your haplogroup is R1b, look at this page; it depicts the distribution of marker values for the most common haplogroup in the project.

Most often, it turns out that it isn't one marker with one big difference from the most frequent value. It's several markers with small differences.

And, remember these facts:

  1. There are only about 550,000 sets of Y-results in the FTDNA database, about 1/8,000th of the world's male population.
  2. Many of these results are for only 12 markers, the lowest resolution level.
  3. The sampling is not even; USA residents are much more heavily represented (up to 90%) than other countries. FTDNA and projects are trying to address the imbalance by testing in other countries.

Match Searching: The Resolution Pyramid

  Resolution Pyramid

As you search for matches, keep the image to the left in mind. It shows the percentages who've tested to the standard FTDNA resolution levels; they form a pyramid. The top is much narrower than the base.


While a 111-marker match may be more reliable than one at 37 markers, many fewer have tested at that level of the pyramid. There are only one-eighth as many opportunities to match. Do not ignore high-quality matches simply because the other person hasn't tested higher.

This overstates the pyramid's widths at higher resolutions. The percentages are for Taylor Family Genes members. Relative widths for other projects and the entire FTDNA database are narrower. 

Match Interpretation

Interpreting the specific meaning of a match can become complex because `it relies on probabilities. We need them because DNA mutations are random events and can not be predicted in absolute terms. While probabilities are widely used in science, many people are uncomfortable with probabilistic statements.


The purpose of Y-DNA match interpretation is to decide whether a found match is worth pursuing. Does it warrant the hard, slogging documentary research needed to identify the CMA by name, dates, places and other specifics?

Simplified Interpretation

FTDNA has produced a simplified guide to interpreting Y-DNA matches, classifying them into six "relatedness" categories. Click here to view. This guide is, we think, a bit over-simplified -- especially in regard to 12- and 25-marker matches. The statements are not wrong, per se, but one should place low confidence in them.


The quality of the match will largely determine the time to the most recent common ancestor (TMRCA). You may want to read our page on this subject.

Transmission events (TE)

We usually do not know the Y-DNA haplotype of the common male ancestor (CMA) in a match. We only know the similarities and differences between samples of two or more living Y-DNA donors. As we work back through the diverging lines  to the CMA, we need to consider the possibility of mutations in either or both lines.

A transmission event (TE) occurs when a parent passes DNA to a child and the DNA has an opportunity to change. Transmission events are the spaces between generations and we need to account for the TE in both lines. Within the same time window there will be two sets of TE, one for each line.

Diverging lines from CMA
The diagram above depicts the transmission events in two lines diverging from a CMA. The total number of TE in this example are 12 (7+5). The two donors are separated by 12 TE.

Think of transmission events as all the generations in one donor's line from the CMA plus all the generations in the other donor's line from the same CMA minus the two donors' generation. It's similar to the "degrees of separation" game.

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We should be cautious about the implied precision of the statistics for these reasons.

Despite these cautions, we believe the calculations given below are adequate to answer our underlying question: "Is this match worth investing my time and effort?"


That DNA mutations are essentially random means that they can only be interpreted through probability theory.

Probability has no "sure things"; words like chance & odds permeate throughout. The type of probabilities we look for are are "cumulative"; they represent the chances of sharing a CMA within a specified number of transmission events. Here are typical graphs for 37 & 67 markers. Click the graphs to see larger versions.

Cumulative Probability
37-marker match cumulative probabilites 67-marker match cumulative probabilities
For a 37/37 (0:37) match, chances of the donors being separated by no more than 10 TE are ~80%. For a 67/67 (0:67) match, chances  of the donors being separated by no more than 10 TE are ~90%.
Probability Per Generation
The cumulative probabilities shown above are derived from sums of individual per-generation probabilities depicted below.

Note on the graphs: The probabilities shown are rough approximations. Which markers differ and by how much matters. Markers are not equal in their mutation frequencies; there is, in fact, a wide range -- from an average of 1 mutation per 28 generations for CDY to 1 per >11,000 for DYS426. Thus, a difference in DYS426 is orders of magnitude more significant than one in CDY.

Alternative approaches

Different people relate to information in different ways. Some absorb it one way; others another way. Therefore, we present different approaches, all  based on the same underlying principles that similarity of haplotypes indicate a common ancestor and the degree of similarity the number of generations separating the two sample donors :

  1. Simplified Probability:

    This approach shows a specific time window and simplified probability categories. It answers the question of how likely it is that an observed match indicates a CMA within  time windows of 500 years. 750 years or 250 years. Click here.
  2. TMRCA Calculators:

    Also see our page on TMRCA.
  3. Math & Theory:

    Some want to look under the hood and see what's going on. This page is for them. Click here. (Note: Incomplete)
  4. Other Questions:

    For more information on probabilities for Y-DNA match interpretation, e-mail Ralph with your question.

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Triangulation & Networks

When matches exist in a group of three or -- preferably -- more it may be possible to estimate the CMA's haplotype and use differences from that estimated haplotype to determine specific branches with that family's tree. This is a refinement on match interpretation which can only be employed for matching groups (genetic families) of adequate size. Triangulation is a complex subject and it's discussed in more detail on our "Triangulation" page here.

With groups of three or more, it is also possible to construct a network diagram to pictorially depict the genetic branches of the family. We have used the Fluxus Network software to build diagrams of qualifying Taylor genetic families. A collection of these diagrams can be found here.


When a high-quality, genealogically significant match is found, your fun has just begun. You will want to contact the other party (& he or she to contact you) to share information toward the goal of identifying the common male ancestor. Perhaps, you both descend from different sons of the same father.

You will want to ensure that your contact information is available to the person with whom you match, so keep it current. In these days, e-mail addresses are especially important. Most people will use e-mail primarily.

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Along with the STR markers & allele values, FTDNA will report the predicted haplogroup into which your DNA falls; if it is unable to predict, its SNP Assurance Program will, on request, conduct additional "backbone" testing to definitively establish the haplogroup. You may also order analysis of some SNPs to specifically identify the haplogroup and its subclade.

A haplogroup identifies broad groups of different yDNA strains -- main branches on the human family tree. Because haplogroups are associated with particular places, this tells you something (e.g., ethnicity & geographical origin) about your distant paternal forebears who are otherwise lost in the mists of time before recorded history. A haplogroup determination speaks to deep ancestry; it is less useful within genealogic time.

Haplogroup names

Two systems are in use for naming haplogroups:
  1. Phylogenetic name

    The "old system" in which the name refers to a specific position on the human phylogenetic tree.
  2. Shorthand name

    The "new system" in which the name refers to an SNP which defines the haplogroup.

A haplogroup's phylogenetic name starts with a capital letter, which may be followed by alternating numbers and letters, e.g., "R1b1a2a1a2c". Each number and letter further refines the designation, but does not change those which precede it. R1b1 and R1b2 both belong to the broader group, R1b. The problem with the phylogenetic system is that the name changes when scientific discoveries cause change to the tree's structure. (This has been happening at a rapid rate.)

The shorthand system uses the base haplogroup letter and the defining SNP (e.g., R1b1a2a1a is known in shorthand as R-M269). If the tree structure changes, the haplogroup name needn't. The problem is that there is no systematic relationship between SNP names and tree positions.

Haplogroups are further discussed here.

Conflicting Haplogroups

A conflict in haplogroups -- especially if confirmed by SNP testing -- will invalidate a match on STR values. This indicates the match is coincidental, perhaps due to convergent evolution, because the two men can not have a common direct paternal ancestor within genealogic time.

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Glossary, Definitions

Due to the amount of content, we've moved this section to a "glossary" page. If the definitions in the list do not display, click here.


Success Stories

Our project members have had genetic genealogy success stories to share. Here are a few with the names deleted.

Technical Information

The human Y chromosome contains 58-60 million base pairs (abbreviated Mbp or Mb). It contains about 458 genes, making it "gene-poor" with respect to other chromosomes. It's one of those genes, though, (SRY in region 1) that's responsible for defining a male.

The Y recombines (exchanges information) with an X chromosome only in the two psuedo-autosomal regions (PAR1 & PAR2) at its ends. Most of the Y does not recombine with other chromsomes, rendering it useful for tracing paternity.

Some sources for technical information about the human Y chromosome include:

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Revised: 18 Sep 2016