Family Finder uses in excess of 700,000 Autosomal SNPs to help find relatives from all parts of one's family tree. Previously, DNA genealogy tests could only tell a person about a small part of their family tree based on DNA from the Y chromosome and mitochondria. By using Autosomal DNA (abbreviated as atDNA), Family Finder can trace any ancestral line, no matter where it is in the family tree. The test identifies matching segments of DNA. The size and number of shared segments will help to predict the possible relationship.
The science behind this involves comparing the atDNA of all participants to discover total Centimorgans (abbreviated as cMs) to determine up to and including 2nd cousins, then for 3rd cousin and higher they use largest cMs plus a formula to determine these as follows:
- 1st longest block
- 2nd longest block over 5
- total of all cMs
on 500 SNPs or more.
To see some examples of Family Finder results for known close relationships see the screenshots in the separate article on Chromosome Browser Examples.
Steps to find your common ancestor for matches at Family Tree DNA
On your Personal Page in Family Finder, on the left hand column under Family Finder, you will see the heading Matches. If you select that it brings you to your Family Finder Matches. Usually shown are the Close and Immediate Matches. You can also choose other Filter Matches such as Speculative or Close Relative.
When you receive a match in Family Finder, the first thing you must consider is the Suggested Relationship, as well as the Relationship Range. This gives you what the company feels your possible relationship is, with the Relationship Range giving you a range of where the actual relationship may be. Understand that relationships can also be outside of this range, as well, as testing autosomal DNA is not an exact science due to recombination.
Next look at the Shared cM (centimorgans) and Longest Block listed for the match. The combination of this information is what Family Tree DNA uses to determine your possible relationship. Another helpful tool on this page is the Ancestral Surnames. You can check your matches surnames to see if you may connect on a particular surname or surnames for further research.
Next go to Chromosome Browser which is on the left side of the screen under the Family Finder heading.
You can select a single match under Filter Matches By… or up to five matches under Compare Genes. Once you make your selection(s), choose View This Data in a Table on the right side of the screen, and you will see the following information:
|| Start Location
|| End Location
|| Matching SNPs|
This gives you the chromosome(s) where you match; the start and end locations for that match; the total cMs for that location, and how many Single-nucleotide polymorphisms (SNPs) matched. You will be looking for the longest block of cMs which, in this case, is 12.94 and any other blocks over 5.00. Using the longest block of cMs, you can use the following Match Outcomes list (below) to give you an idea of where your actual relationship may lie.
- 10 cMs or higher indicates a match usually within 5 generations (4th or more recent cousins)* - better chance to find a match with a highly developed genealogy
- 5-9 cMs can cover a range of 6 to 11 generations (5th to distant cousins)* – later generations may include low level matches that show you probably share a common ancestor but may not be able to effectively trace genealogically
- Below 5 cMs (Mb) gives ancient ancestry
A generation can run an average of every 25–35 years. To understand generations and cousinship levels, check the following chart courtesy of Family Tree DNA FAQ.
These features can be found on your FTDNA personal page under User Preferences:
Personal Image: You have the option to insert a personal image or photo in your profile.
Ancestral Surnames: You have the option to list your Ancestral Surnames and Countries. List as many surnames from your genealogy as you can regardless of what generation they are in. Some matches have been made as far back as ten generations. List just the surname in the Surname field. Variant spellings should be listed as separate surnames. It is a good idea to list dates as well as locations in the Country field. Some people have listed the country with the state, county or province in parenthesis. Others have listed the county, province or state names first followed by the country with dates in brackets (see screenshot below). Avoid using abbreviations wherever possible. Remember that FTDNA has an international database. US state abbreviations for example will not be very familiar to your European matches.
After you have entered your ancestral surnames, you might notice that some of the ancestral surnames of your matches are highlighted in bold type, indicating that the highlighted surname might match one of yours. Note that Family Tree DNA is using a surname-matching algorithm that is somewhat liberal. For example, some pairs of surnames that it considers to be a potential match are BROWN and BRUN, NEELY and NEIL, PEGG and PIKE, and THORN and TRAHAN.
Why is my relationship listed as 5th cousin to distant when I have a longest block over 10 cMs?
Family Finder uses a combination of the longest block of cMs and shared cMs to determine relationships. Sometimes there is a block larger than 10 cMs that is assigned a more distant relationship because of a smaller number of shared cMs. For example, you may have a match in Chromosome 5 that lists 15.31 cMs in the Longest Block, but only 27.93 in Shared cM. This is an anomaly. What happened is that cMs that we shared from our ancestors got broken down in all the other chromosomes except the one large block in Chromosome 5. This block should have broken down too but was in a place that did not recombine the same as the others. That is why FTDNA did not place it at a nearer cousinship. They usually place situations like these one cousinship back to distant.
As an add-on to Family Finder, Family Tree DNA compares the DNA results with reference samples from several populations around the world and attempts to identify the sources of one's DNA on a continental level. Below are two examples, the first of which is for an individual whose DNA is estimated to be 97.07% European and 2.93% Native American.
The example below is for a child of the above example. The child is reported to be 98.25% European. The remaining 1.75% for the child is not reported as it likely falls below a confidence level for accurate assessment.
For an explanation of the workings of Population Finder and the meaning of the Middle Eastern percentages seen in many Population Finder results see the guest blog post by Doug McDonald on biogeograpical analysis.
See also Roberta Estes' blog post on the dreaded "Middle East" autosomal result.
Family Finder reviews
- Family Finder review from Terry Barton 11 March 2010
- The new Family Finder test from FTDNA by Debbie Kennett 30 April 2010
- A Review of Family Tree DNA's Family Finder – Part I by Blaine Bettinger 19 July 2010
- A Review of Family Tree DNA's Family Finder – Part II by Blaine Bettinger 5 August 2010
- Autosomal DNA testing comparison chart
- Autosomal DNA statistics
- Autosomal DNA tools
- Family Finder project
- Family Finder versus Relative Finder
- FTDNA Family Finder official website
- Family Finder FAQs Official FTDNA FAQs page
- Family Finder demo
- "Autosomal DNA: The New Revolution - Part 2" ISOGG Newsletter, Mar 2010
- Family Finder introductory video on YouTube: