How to get the most out of your DNA results
1:30 a.m. Tuesday 9 November 2021 (Irish time)/5:30 p.m. Monday
8 November 2021 (Washington time)
DNA testing is not a substitute for genealogical
research; rather the two approaches help to corroborate each
DNA is as much part of finding your roots today as is consulting
census returns, and can help to break down brick walls in your
Genealogists compile family histories by matching up three
categories of information:
The boundaries between oral and archival can be blurred:
- the oral traditions passed down through the generations;
- the archival sources used by traditional genealogists; and
- the DNA evidence that often reconciles both, but sometimes
refutes either or both (NPE).
Stanford historian Richard White wrote in his family history Remembering Ahanagran: Storytelling in
a Family's Past (Cork University Press, 1999, p. 4):
- Is the description of the deceased provided by the informant
on a death certificate oral or archival? (Estimated age at
death, parents' names, mother's maiden surname, etc.)
- Are family letters and diaries oral or archival?
- Are published or unpublished family histories oral or
archival? (e.g. 1991 Cosgrove-Corry by
Peter Ryan at al.)
I once thought of my mother's stories as history. I
thought memory was history. Then I became a historian, and after
many years I have come to realize that only careless historians
confuse memory and history. History is the enemy of memory. The
two stalk each other across the fields of the past, claiming the
same terrain. History forges weapons from what memory has
forgotten or suppressed. Few non-historians realize how many
scraps a life leaves. These scraps do not necessarily form a story
in and of themselves, but they are always calling stories into
doubt, always challenging memories, always trailing off into
The emergence of genetic genealogy has turned this two-way struggle
between memory and history into a three-way battle.
Identity v. Anonymity
- There is a trade-off between:
- increasing your chances of finding long-lost cousins and
ancestors (and being found by long-lost cousins); and
- maintaining the privacy of your family history research and
- If you keep your DNA results or known family tree private,
then nobody will be able to find you and you will not be able to
find any DNA matches.
- If you want to be found, then you must let your potential
cousins see your DNA results and your known family tree.
- Some customers of the DNA companies appear to wish to maintain
a certain degree of privacy and anonymity
- Others find it paradoxical that those trying to identify their
anonymous ancestors can be so concerned about anonymising their
The Genetic Information Nondiscrimination Act of 2008 has caused
- health insurers may not discriminate against people
with bad genes by charging above average premiums
- health insurers must discriminate against people with
good genes by charging average premiums
- pension providers could discriminate against people with low
life expectancy by charging as if they had average life
- can pension providers charge people with high life expectancy
more than if they had average life expectancy?
rules for genetic genealogy
- Reveal your birth surname:
- Most people inherit DNA with their birth surname, so identify
yourself as a minimum by your birth surname with an initial or a
title, e.g., P Waldron or Mr Waldron or Miss Durkan.
- Reveal the gender of the person who provided the DNA sample:
- Valuable additional inferences can potentially be drawn once
it is known whether two X chromosomes (chromosomally female) or
one X chromosome and one Y chromosome (chromosomally male) are
potentially available for comparison.
People who are chromosomally female do not have Y-DNA and are
encouraged to recruit their chromosomally male relatives to
provide Y-DNA, but they must NOT attach a female name to a male
DNA sample, as this causes untold confusion.
Be especially careful not to inadvertently link a male's Y-DNA
results with a female's autosomal DNA results at
FamilyTreeDNA.com where error-checking does not look for this.
- Avoid providing irrelevant information:
- Your first name, married surname, adopted surname or marital
status reveal nothing about your DNA, so you may keep these
private if you wish.
- Avoid pseudonyms and aliases:
- They reduce the chances that your matches will bother to look
at your family tree, contact you or share the information about
your ancestry that they have and that you do not have.
- Be consistent and avoid unnecessary confusion:
- A real example (further anonymised):
- AncestryDNA username: tara1234
- DNA samples from mother and daughter (per email exchange)
- linked to an aunt and niece in a family tree
- appear to matches as M.R. (managed by tara1234) and D.C.
(managed by tara1234)
- neither of these are the real initials
- the daughter is an AncestryDNA match to her mother's
probable 4th cousin, but the mother is not (false negative?)
- only one of the two kits is at GEDmatch.com
- GEDmatch alias and email address both begin with Molly
- Molly is the dog's name
- it took me 300 days after the upload to GEDmatch to
associate the AncestryDNA and GEDmatch identities
- Keep all your DNA-related correspondence in a single
searchable email archive
- Use the messaging systems on the DNA wesbites and social media
websites only to exchange email addresses.
What is DNA?
- short for deoxyribonucleic acid
- made up of chromosomes and mitochondria, each consisting of
molecules of four nucleotides
named adenine (A), cytosine (C), guanine (G) and thymine (T)
- represented by strings of the letters A, C, G and T
- laboratories produce a computer file (raw data file) of As,
Cs, Gs and Ts from DNA samples
Where does our DNA
- When a sperm fertilises an egg, each brings DNA, which is
replicated in every cell of the resulting person.
|22 paternal autosomes
|22 maternal autosomes
- autosome is short for
- Y chromosome
- Only males have a Y chromosome.
The Y chromosome comes down the patrilineal line virtually
unchanged - from father, father's father, father's father's
This is the same inheritance path as followed by surnames,
grants of arms, peerages, etc.
- X chromosome
- Males have one X chromosome, females have two.
X DNA may come through any ancestral line that does not contain
two consecutive males.
Blaine Bettinger's nice colour-coded blank fan-style
pedigree charts show the ancestors from whom men and women can potentially inherit X-DNA.
- Exactly 50% of autosomal DNA comes from the father and exactly
50% comes from the mother.
Due to recombination, on
average 25% comes from each grandparent, on average 12.5% comes from
each greatgrandparent, and so on.
Siblings each inherit 50% of their parents' autosomal DNA, but
not the same 50% (except for identical twins).
Similarly, siblings each inherit 50% of their mother's X DNA,
but not the same 50% (except for identical twins).
Sisters each inherit 100% of their father's X DNA.
- Everyone has mitochondrial DNA.
- Mitochondrial DNA comes down the matrilineal line - from
mother, mother's mother, mother's mother's mother, etc.
The surname typically changes with every generation in this
- Autosomal DNA is widely used in genealogy.
- Y DNA is used for one name studies or surname projects.
- Targeted mitochondrial DNA and X DNA comparisons can be used
to solve more specialised problems.
- Autosomal matches can be related through either parent and
through any grandparent, greatgrandparent, etc.
- In principle, Y DNA matches should share the DNA subject's
- In practice, Y DNA matches can have different surnames:
- because the common ancestor lived before the surname era
(about 1000 years ago in many cultures); or
- because there has been a surname/DNA switch (a baby boy took
his surname from mother, stepfather, adoptive father, or
anyone other than his genetic father).
autosomal DNA comparison websites
You must link your DNA match list
and your pedigree chart and
share them on the major autosomal DNA comparison websites:
The pedigree chart should include names, dates and places for as
many generations of ancestors as possible, say five generations.
difficult to recommended for genealogy as it is limited to
two-generation pedigree charts with places only, but no names or
Websites may accept raw data files:
- from their own laboratory only (AncestryDNA, 23andMe)
- from other laboratories only (GEDmatch)
- from their own laboratory and other laboratories
So the cheapest way to get into the system and fish in all the
gene pools is:
- spit for AncestryDNA and 23andMe
- upload the resulting raw data file to GEDmatch, FamilyTreeDNA
You are more likely to find confirmed relatives on the DNA
- the more customers the website has
- the better the analysis tools the website provides
The DNA Geek provides regular updates on customer
How can we use
autosomal DNA in genealogy?
- Autosomal DNA can distinguish unambiguously between identical
twins and fraternal twins
- Sometimes autosomal DNA comparison can tell us that two
individuals are almost certainly full siblings (Group A on the DNA Detectives Autosomal Statistics Chart)
- In other cases it may not be clear whether we are looking at
full siblings with below-average shared DNA or half-siblings
with above average shared DNA
- Sometimes autosomal DNA can tell us that two individuals
almost certainly have one of the relationships in Group B
(half-siblings, aunt-or-uncle/niece-or-nephew, double first
- Evidence of age and evidence from the other parts of the DNA
(X, Y, mt) can be combined with the autosomal DNA evidence to
narrow down the possible relationships
- Occasionally autosomal DNA comparison can tell us that two
individuals almost certainly have a Group C relationship (first
- But generally autosomal DNA comparison can only give us an estimated probability distribution of the
possible relationship groups.
- Some DNA companies still give conflicting relationship
estimates for the same match (example)
- Less informed customers may not understand the difference
between an estimated relationship (based on DNA) and an exact
relationship (based on a paper trail).
The DNA company to which you pay your money and send your sample has
a number of priorities, in this order:
- separating you from your money;
- assigning ethnicity labels to percentages of your DNA; and
- sending you elsewhere for help in identifying cousins and
pedigree charts and DNA results
- Add DNA information to your genealogy database:
- Beginners may not be familiar with the term pedigree chart, let
alone GEDCOM file.
- As soon as you have sent off your DNA sample, you must
start recording your ancestors and cousins confirmed by DNA
in a database using software like Ancestral
- You can combine your DNA and your known ancestry to help
your long-lost cousins to find you and to find your and
their long-forgotten ancestors.
- Use an event field or note tag in your database to track
people who are in both your database and the DNA databases.
- Add genealogy information to the online DNA databases:
- Export a GEDCOM file containing at least the ancestors of
each DNA subject and upload it to all the DNA websites.
- Examples of pedigree charts: from Ancestral Quest, AncestryDNA, ancestry.com, FamilyTreeDNA and GEDmatch.
- For FamilyTreeDNA.com, include in the GEDCOM file any
known relatives already in your FTDNA match list and the
shared ancestors; FTDNA will use this information to assign
other matches to the DNA subject's paternal and maternal
- Add your GEDmatch.com kit number to WikiTree.com
and GEDmatch.com will automatically display a link to your
pedigree chart on WikiTree.
autosomal match lists and segment data from the different DNA
DNApainter.com is one
of several tools for aggregating:
- the match lists provided by all the DNA websites; and
- the segment data provided by all the DNA websites except
A case study:
the Lynches of Moveen West
- Pádraig Máire Neans (b. Abt 1826/9, d. 1907) and Tomás Máire
Neans (b. Abt 1838/41, d. 1921) are remembered in the oral
tradition as two Lynch brothers living across the road from
each other in Moveen West.
- They survived the Great Famine in Moveen.
- Their mother Máire/Mary is remembered as one of two sisters
between whom an O'Dea farm was divided - Mrs Lynch and Mrs
O'Connell (later evicted?).
- In Griffith's Valuation in 1855, Mary Lynch
(apparently widowed, no. 9a) and her son Patrick Lynch
(recently married, no. 24a) are listed as occupiers.
- A third Lynch brother, Daniel, went to Connecticut, where
his death certificate confirms his parents'
Daniel Lynch, Newtown, Aug 4, 62, male, married,
County Clare, Ireland, Newtown Conn, Paralysis Caused by
fall, Farmer, W, Michael Lynch, Mary O'Day, Albert L
[3rd last line on each page]
- Daniel is buried in St. Rose's Cemetery in Sandy Hook.
- 20 June 2016: Donation from the diaspora to Clare Roots project "to go towards the
test cost for a descendant of the Moveen West Lynch families".
- Around the same time, the Lynch siblings of Sacramento began
to show up as autosomal DNA matches to "all the usual suspects"
- people with roots on the Loop Head peninsula in West Clare.
- What they then knew about their Irish-born grandfather:
Because our grandfather, Eugene Lynch, is such a
mystery to us we really don't know how to find him. All we
have for certain is the 1910 census [lines 39-43]. It says
he came over in 1887. The story is this: Eugene married my
grandmother in San Jose in 1904 and they lived in Sacramento.
He abandoned her and their children in 1909 [sic] when my
grandmother was pregnant with my father. We didn't really know
anything about him until we started doing this genealogy. We
knew [sic] he died in San Francisco in 1917 but were surprised
to discover that he was the captain of a schooner at the time.
- 6 October 2016: I uploaded the new recruit to GEDmatch.com and
found this triangulation:
8 8,292,285 54,555,905 50.2 10692 Claire/Ed
8 17,609,398 38,378,638 27.4 5563 Ed/Michael
8 17,648,866 37,812,773 26.9 5499 Michael/Claire
- Claire and Ed are fourth cousins, descended from Mrs Lynch and
Mrs O'Connell respectively.
- So their 50.2 centiMorgan half-identical region must contain
an O'Dea segment.
- Michael is Eugene Lynch's grandson, so Michael must be related to Mr O'Dea
(first name still unknown) or Mrs O'Dea (Neans) or descend from
- Eugene's surname is Lynch, so he must descend from Michael Lynch
and Mary O'Dea.
- Eugene (41 in 1910) is too young to be Michael and Mary's son
(their known children have implied birth years 1824-1841).
- Eugene's baptism is not in the parish registers, which
- Eugene's descendants share too much DNA with other descendants
of Michael Lynch and Mary O'Dea for him to be their
- So he must be their grandson.
- Even this implies a somewhat implausibly large 209.5cM shared
between 3C1R - see Autosomal Matrix Comparison and Table of Probabilities.
- 15 November 2016: The Sacramento Lynches arrive in Moveen:
That day was the highlight of our trip to Ireland,
and for me it was an unbelievable gift. I have been wondering
and imagining for so long about my grandfather's (and thus my
own) origins that I still quite can't believe I went there. It
was a profound and moving experience for me. My sister Pat and
I speak of it often ... It was magical to us. Both of my
parents were from families who didn't stay connected with
their homeland, and this journey has really fulfilled a need
that I hadn't realized I had. I'll be forever grateful to Tom
Kearney for introducing me to you, and to you for so
generously sharing your expertise with us.
- For over two years, we swabbed various descendants of the
known sons of Michael Lynch and Mary O'Dea in search of closer
matches and of further clues, but failed to identify Eugene
- 8 March 2019: The Sacramento Lynches return to Moveen (Facebook post).
- An epiphany on the road to Moveen - a new hypothesis to be
tested: Could Eugene have taken his mother's surname?
- No sign of a Eugene Lynch born to a single mother in the local
- We have analysed autosomal DNA matches extensively, but did we
ever check Michael Lynch's Y-DNA matches?
- The Y-DNA and the surname both follow the male line, unless
there is a surname/DNA switch.
- Not a Lynch to be seen in Michael's matches
- Two Currys out of nine Y-DNA111 matches.
- Four more Coreys or Currys (including an adoptee), none of
whom has bought Y-DNA111, in his top 12 Y-DNA67 matches.
- Surname spellings also mutate, independently of DNA mutations.
- Corey, Corry, Curry, O'Curry, Ó Comhraí should all have the
same Y-DNA signature; likewise Lynch, Lindsey, Lynskey,
Lynchahaun, Lynchaghaun, etc.
- Could Eugene Lynch really be another Eugene O'Curry?
- Not the parent expected? (NPE)
- The DNA evidence often fills gaps in the traditional evidence,
but sometimes refutes it.
- His famous namesake reputedly descends from the O'Currys of
Lisluinaghan (see repeatedly evaporated Rootsweb post).
- The Mary Lynch who married Thomas Corry/Curry of Lisluinaghan
appears to have been a daughter of Michael Lynch and Mary O'Dea:
- 98.5 centiMorgans shared between a descendant of Daniel
Lynch and a descendant of Mary Curry, who could be no closer
- Pat Corry from Lisluinaghan witnessed the shotgun wedding of Michael Lynch of
Moveen in 1882 - were they first cousins? Or even double first
- Thomas Curry and Mary Lynch had a youngest son called
Eugene, baptised in Kilkee parish on 10 Apr 1866:
- "this ancestor has been very elusive";
- he had "previous";
- no sign of Eugene Curry in 1900;
- his wife Ellen Curry née Kelly was a live-in servant in Brooklyn (line 48);
- Ellen's sister Mrs Margaret Blomberg was taking care of
Eugene and Ellen's daughter Margaret in Brooklyn also (line 93);
- Eugene's brother Simon Corey was taking care of Eugene and
Ellen's daughter Elsie in Newtown, CT (line 96);
- the family lore passed down has always been that "Eugene
Curry “went west” to find his fame and fortune and would send
for his family at a later date. He was never heard from
- 209.5cM shared between 2C1R makes a lot more sense
than 209.5cM shared between 3C1R.
- "The idea of the two Eugenes being one is a bit staggering and
mind-boggling" for his descendants, and even for me.
- Further investigation of the DNA matches shared by known Lynch
and Corry descendants in different DNA databases has left little
doubt that Eugene Curry became Eugene Lynch.
Why you should submit your DNA
- The value of DNA "testing" to genealogists
increases dramatically with the number of people from the
relevant geographical area and relevant extended family group
already in the DNA databases used.
- Submitting your DNA to a database has
significant positive externalities for existing and future
- We need to persuade more people to submit DNA samples to the
databases for purely genealogical purposes.
descendants will be eternally grateful to you for leaving
them your DNA.
- See here for all the technical details of how
and why to upload your DNA data and pedigree charts to the