Family Finder

Family Finder Autosomal Test

The Family Finder test is mainly used to get matches with relatives where you share ancestry within 5 generations, and to discover indication about ethnic ancestry through the MyOrigins component.

FamilyFinder

What can the Family Finder test be used for?

The test can be used to:

  1. try to verify common ancestry by testing several descendants of the same person – triangulation – more than five generations back will not give unambiguous matches
  2. discover more relatives who can be anything from close to distant tenth cousins – this is ideal for adoptees who are searching for information about biological family, but also for others who wish to extend their family tree ad trace common ancestry
  3. discover indications of new geographical areas where ancestors can be from based on matches’ locations, further back than historical documentation (not exact information to extend one’s tree)
  4. find out about ethnic ancestry via MyOrigins, however not accurate since the analysis depends on available reference populations.

Challenges in tracing common ancestors

  1. Complete genealogy with all ancestors in the tree for a minimum of 7 generations needed to thoroughly evaluate matches
  2. More than five generations back to a common ancestor will only give a match with some of the tested relatives in the line, not all, see overview with percentages
  3. It can be difficult and time-consuming to evaluate all possible connections in the tree for a match
  4. If your ancestry is concentrated within a geographic area or ethnic group, you will often be genetically related to everyone there

Estimated degree of matches from FTDNA

If all your relatives were tested, here is the chance for them sharing DNA with you and appearing in your matches list:

  • second cousins and closer: ab 99 %
  • third cousins: ab 90 %
  • fourth cousins: ab 50 %
  • fifth cousins: over 10 %
  • more remote cousins: rare

Many Norwegian testers experience that they also match many seventh to tenth cousins as well, especially if they share several ancestors within the same geographical area.

Also note that because of recombination the matches will be more and more random the further back you get.

autosomal_inheritance

The blogger Blaine Bettinger (The Genetic Genealogist) has described how we have one genealogical tree (with all our ancestors), and one genetic tree (with the ancestors we have actually inherited DNA from).

Anetre

Genetisk anetre

When we are 5 generations back and more, it will be random if we have shared DNA with people of shared ancestry.

Genetic-Tree-Ethnicity-Loss BettingerThe ethnic ancestry of the ancestors marked blue will not appear in myOrigins. 5th and 6th cousins with common ancestry from either of the ancestors marked blue will not appear in your matches list in Family Finder.

Background

The Autosomes is the name of the 22 pairs of chromosomes we have that are not gender chromosomes. The complete human genome consists of approximately 2,9 billions SNPs, which can be analyzed. In the Family Finder test a selection of approximately 700 000 of these are analyzed, chosen from areas with good stability. An information video from Sorenson will in simple English explain how autosomal DNA is inherited through recombination.

Contrary to Y-DNA and mtDNA which are inherited literally unchanged through ONE line in the ancestry tree, the autosomes are a mixed combination of practically all branches of our tree. Even if we do not inherit equal amounts of DNA from all ancestors, the DNA segments can come from any line and any ancestor, not only the direct paternal or maternal line.

The results of the Family Finder test will give a list of matches of people in the databse you share DNA segments with. There will be matches with people related to you within 4-5 generations with very high certainty, and also a few matches with more distant relatives; here the matches are more random. If you share a common ancestor more than 6 generations back, there will not always be shared DNA from that ancestor, and this no match in the system.

23andMe explains in a simple video how the test relates to all lines in the tree. The 23-test is similar to FTDNA’s Family Finder, but includes SNPs that reveal health information.

Comparing trees

If you match someone with Family Finder, and the longest block in common is 10 centiMorgans or more, then it is probable that the two of you share a common ancestor, normally within 10 generations or closer.

  • longest block over 10 cM: chance is high to have a common ancestor within genealogical timeframe
  • longest block under 10 cM: might show “populational match”, e.g. descending from the same population, but too far back to trace common ancestry. Might also be IBS; see below.

To find out more about what your matches mean, you need to compare ancestry trees. There are several ways to do this:

We do have a lot of direct ancestors looking some generations back, and not everyone will know all of these for 7-10 generations. The list below shows how many direct ancestors we have in theory, and with generation age set as approximately 33 years for simplicity, with grandparents born around 1900. Generation age of 25 years will give 20 generations around 1500 AD and not 1300 as shown below.

  1. generation: 2 parents
  2. generation: 4 grandparents born around 1900
  3. generation: 8 great grandparents born around 1866
  4. generation: 16 2. great grandparents born around 1833
  5. generation: 32 3. great grandparents born around 1800
  6. generation: 64 4. great grandparents born around 1766
  7. generation: 128 5. great grandparents born around 1733
  8. generation: 256 6. great grandparents born around 1700
  9. generation: 512 7. great grandparents born around 1666
  10. generation: 1024 8. great grandparents born around 1633
  11. generation: 2048 9. great grandparents born around 1600
  12. generation: 4096 10. great grandparents born around 1566
  13. generation: 8192 11. great grandparents born around 1533
  14. generation: 16 384 12. great grandparents born around 1500
  15. generation: 32 768 13. great grandparents born around 1466
  16. generation: 65 536 14. great grandparents born around 1433
  17. generation: 131 072 15. great grandparents born around 1400
  18. generation: 262 144 16. great grandparents born around 1366
  19. generation: 524 288 17. great grandparents born around 1333
  20. generation: 1 048 576 18. great grandparents born around 1300

In reality the number of actual direct ancestors will be much lower due to Pedigree Collapse. The population in Norway is estimated to have been around 150 000 after the Black Death in 1350. Consequently, the probability of being distantly related will be very high for people from the same area of Norway.

Is a Match always a Match?

If you share segments smaller than 11 cM note that these can be random, IBS and not inherited common DNA (IBD):

IBS = Identical By State = by chance

IBD = Identical By Descent = inherited

See dna-footprints.com for a longer explanation, blog by Kasandra Rose.

  • 11 cM or greater matching segment: >99% IBD, <1% IBS
  • 10 cM matching segment: 99% IBD, 1% IBS
  • 9 cM matching segment: 80% IBD, 20% IBS
  • 8 cM matching segment: 50% IBD, 50% IBS
  • 7 cM matching segment: 30% IBD, 70% IBS

 

Learn more

Statistics for autosomal matches and shared DNA (ISOGG’s wiki).

ISOGG: Comparison of autosomal tests from FTDNA Family Finder with 23andMe Relative Finder, Ancestry DNA (ISOGG’s wiki).

More information from FTDNA on Family Finder:

FAQ on FF myFTDNA home page

FAQ on FF, Understanding Results

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