Using DNA to fill gaps in family histories
3:15 p.m. Saturday 10 March 2018
City Library & Archive, 138/144 Pearse street, Dublin 2
Family history flows down through the generations via three
Talk to your known relatives and correspond with your closest DNA
matches. Sometimes the gaps left by one individual's
sources can be filled by those of a known or unknown relative.
- Most genealogists start by writing down the oral traditions
passed down through the generations to older family members.
- Archival sources are then traditionally used
by genealogists to fill some of the gaps in the oral family
- DNA evidence now fills many of the remaining gaps left by
the traditional sources.
The boundaries between oral and archival can be blurred:
All three types of sources must be consulted. None can be ignored.
- Is the description of the deceased 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- Are published or unpublished family histories oral or
- Does each source verify the others?
- Better still, does a new source fill gaps in the others?
- Or are there conflicts of evidence?
The genealogist has to be judge and jury.
- the Killeen family in 1911
- Patrick's greatgrandson and his brother Christopher's
granddaughter share 102.3 centiMorgans (GEDmatch) or 124 centiMorgans
(FamilyTreeDNA) of autosomal DNA
- this is consistent with the distribution of shared centiMorgans
for second cousins once removed
- Christopher's first marriage in 1934
- Christopher's second marriage in 1941
- not the parent expected (NPE)
- what birth or baptism record did Christopher produce before
- the Kellien family in 1901
- who was the one-month-old "nephew"?
- still a mystery
- "nephew" is the English translation of the Irish "garmhac"
- see Clare Past Forum discussion
- garmhac is the Irish word for a younger male relative who
expected to share a quarter of one's autosomal DNA - see DNA Detectives Autosomal Statistics Chart
NPEs can be revealed by oral, archival or genetic sources, most often
by the latter.
This talk will outline the steps necessary to combine your DNA
known ancestry to
long-lost cousins to find you and to find your and their long-forgotten
What is DNA?
- short for deoxyribonucleic
- made up of chromosomes and mitochondria, each consisting of
molecules of four nucleotides
named adenine (A), cytosine (C), guanine (G) and
- represented by strings of the letters A, C, G and T
Where does our DNA come from?
- 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
is short for autosomal chromosome.
- Y chromosome
- Only males have a Y chromosome.
The Y chromosome comes down the patrilineal line - from father,
father's father, father's father's father, etc.
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
Blaine Bettinger's nice colour-coded blank fan-style pedigree
charts show the
ancestors from whom men and women can potentially inherit
- 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
Siblings each inherit 50% of their parents'
autosomal DNA, but not the same 50% (except for identical twins).
- 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 line.
- This talk will concentrate on autosomal DNA.
DNA is also widely used for one name studies or surname projects.
- Targeted mitochondrial DNA comparisons can be
used to address
problems - e.g. did two women have the same mother? or just come from the same female line?
- Targeted X DNA comparisons can also be
used to solve
problems - e.g. did two men have the same mother?
The Autosomal DNA and Genetic Genealogy Websites
You must link your DNA
match list and
your pedigree chart
and share them on the major autosomal DNA comparison websites:
MyHeritage.com only got its matching algorithm working properly in late
2017, so that Jim Palmer was not sure whether
the match which helped to identify his birth mother was genuine.
23andMe.com can not currently be recommended for genealogy for
- it essentially withdrew from the market by showing many, if
not all, of its
customers the message "We are continuing to modify some aspects of DNA
Relatives in preparation for the transition to the new 23andMe
October 2015 until at least May 2017;
- it withdrew further from the established market in August
becoming the first of the large companies to switch
to a GSA chip which is not compatible with the current
- it appears to have stopped hosting any type of family trees
for its DNA customers.
Commercial and Marketing Priorities
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
(percentages based on centiMorgans, SNPs, base pairs or what?); and
- sending you elsewhere for help in finding cousins and
Before you get
your DNA results ...
- As soon as you have sent off your DNA sample, prepare
to combine your pedigree chart with your DNA results.
- Beginners may not be familiar with the term pedigree
chart, let alone GEDCOM
- Examples of pedigree charts: from TNG, Ancestral Quest, AncestryDNA, ancestry.com, FamilyTreeDNA
- You must use
your favourite genealogy software (e.g. Ancestral
Quest) to record your ancestors and cousins and
prepare your pedigree chart.
- Register at GEDmatch.com.
- Export a GEDCOM file containing at least the ancestors
of each DNA subject for upload to the relevant DNA websites (AncestryDNA,
FamilyTreeDNA, GEDmatch, MyHeritage).
FamilyTreeDNA.com, include in the GEDCOM file any third cousins or
closer already at FTDNA and the shared ancestors; FTDNA will use this
information to assign other matches to the DNA subject's paternal and
maternal sides (example).
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);
- maintaining the privacy of your family history research
and DNA results.
- 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
- Some customers of the DNA companies appear to wish to
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 own identity.
The Basic Rules
- 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 (female) or one X chromosome and one Y chromosome (male)
are potentially available for comparison.
Women do not have Y-DNA and are encouraged to
recruit their male relatives to provide Y-DNA, but they must NOT attach
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 or marital status reveal nothing about your DNA, so you may
keep these private if you wish.
- Avoid pseudonyms:
- They reduce the chances that your matches will find you or 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):
- Ancestry username: tara1234
- AncestryDNA samples from mother and daughter (per
- linked to pedigree charts of an aunt and niece
- appear to matches as M.R. (managed by tara1234) and
D.C. (managed by tara1234)
- neither of these are the real initials
- mother's GEDmatch alias and e-mail address both begin
- Molly is the dog's name
- it took me
- 300 days after the mother's GEDmatch upload
to associate her AncestryDNA and GEDmatch identities
- 2 days to get her to upload her daughter's data
- Keep all your DNA-related correspondence in a single
searchable e-mail archive
- Use AncestryDNA or Facebook messages only to exchange
After you get
your DNA results ...
- Download your raw data from FTDNA or AncestryDNA
and upload to GEDmatch.
- If you used the AncestryDNA lab, use the free autosomal
transfer to upload the raw data to FTDNA.
- Create and upload an updated GEDCOM file with any new close
cousins or ancestors that come to light.
- Add DNA information to your genealogy database: use an
event field or note tag in your database to
people who are in both your database and the DNA databases.
How can we use DNA in genealogy?
- Autosomal DNA can distinguish between identical twins and
- 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
siblings with below-average shared DNA or half-siblings with above
average shared DNA.
- Sometimes autosomal DNA can tell us that two individuals
certainly have one of the relationships in Group B (half-siblings,
aunt-or-uncle/niece-or-nephew, double first cousin,
- 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 cousin,
- But generally autosomal DNA comparison can only give us an estimated probability distribution
of the possible relationship groups.
- Less reputable DNA companies divide match lists into groups
with misleadingly precise headings like "3RD COUSIN" and "4TH COUSIN".
- Less informed customers may not understand that these
headings are not the exact relationship.
- The observed range of shared cM for various relationships
can also be seen in Blaine Bettinger's Shared cM project and at dnapainter.com.
- DNA PAINTER also allows one to
keep track of which DNA segments have been traced to which ancestor.
Example I: How I found my O'Dea GGGGGgrandmother
Now I am co-administrator of the O'Dea/O'Day/Dee (DNA) Project
(Y-DNA) and we also have an O'Deas of Newtown project
- My Family Finder results are dated 15 Nov 2013.
- My paternal and maternal first cousin's results are dated
- Paternal first cousin's closest match had an e-mail in a Texas
- I mentioned this to his namesake, a local historian
in Limerick, on 2 Sep 2014 and
discovered that they were the same person!
- We compared what we knew and found that we both had
ancestors in Ballybrown and were both somehow related to John Smith
(1849-1909) of Adare.
- My GGGGgrandfather John Keas (c1777-1845) farmed first in
Conigar (now part of the Irish Cement site) and then in Ballyveloge,
where he first leased a 145-acre farm in 1819 (Registry of Deeds, book
840 page 259 deed 563759).
- John Keas was grandfather of John Smith.
- The match's GGgrandparents John Ryan and Bridget O'Dea married in Ballybrown, Lurriga
& Patrickswell Catholic parish on 21 Feb 1821 (no. 469).
- Their marriage dispensation is like a DNA report - it tells us
that they were second cousins but doesn't identify their shared
- John Smith (who married into the business in 1877) employed
the young Denis
Ryan (1858-1928), grandson of John Ryan and Bridget
O'Dea, and is
reported to have later said to Denis Ryan: "Why didn't you tell me you
were related to me?"
- Lease of Ballyveloge "for and during and untill the full
end and term of the natural life and lives of Edward Keas, 2nd son, of
the said lessee and John Keas, 3rd son of said lessee and William Keas,
6th son of the said lessee" (Registry of Deeds, Book 858 page
327 deed 572827)
- Edward Keas remained in Conigar when the rest of the Keas
family moved, in about 1819, from a parish
with no surviving baptismal records today (Mungret) to an adjoining
parish with surviving baptismal records (Ballybrown, Lurriga &
- John Keas and John Keas Jnr., although apparently Catholic,
signed the minutes of a Vestry of
the Established Church
legally called and held at Kilkeedy Church (now in ruins) on 17 Dec
- William Keas was baptised
in Ballybrown, Lurriga & Patrickswell on 31 Oct 1821
"ex Joanne Keas et Maria O'Dea" (no. 1798).
- So John Smith and Denis Ryan each had an O'Dea grandmother!
- Were they sisters? Or is the age difference too large?
Maria's last child was born the year that Bridget married.
- Almost certainly both were daughters of Edward O'Dea, after
whom they named sons.
- Other probable and possible siblings include Anna O'Dea, possibly William Keas's godmother of that name, who married James
Patrickswell parish on 7 Jun 1825 and had children baptised in
Sixmilebridge parish between 1832 and 1844.
- But which of the many James Frosts in that parish was
- Relationship diagram
O'Dea GGGGGgrandparents' grave
- But whatever became of William Keas?
Example II: How I helped my 4th cousin to find multiple
generations of Clancy ancestors
Now I am co-administrator of the Clancy Surname (DNA) Project.
- DNA has let the genie out of the bottle as regards secret
adoptions and fosterings.
- This is the story of how several Down(e)s descendants found
- 10 June 2015: Downes descendant from New York approaches Clare Roots Society in
advance of a 50th birthday first-ever visit to his ancestral homeland
and wrote about his visit.
- 19 June 2015: Dana Downs shows up with by far my biggest
half-identical region with a stranger thrown up in almost two years of
12 93,176,484 125,287,936 44.6 8319 Paddy/Dana
- 8 July 2015: William Brown e-mails me about a GEDmatch
match to my maternal first cousin:
4 102,789,472 114,229,035 10.3 2079 Bill/Mary
- But I noticed that he also matched Dana:
12 24,432,115 60,468,339 30.1 7961 Bill/Dana
15 22,377,651 30,755,131 19.3 1868 Bill/Dana
- All three people descend from Downes emigrants who left
house in County Clare.
- Two of the three emigrants had children born out of wedlock
who were brick walls for their descendants, prompting them to
submit DNA samples.
- Bill and Dana are double third cousins once removed.
- Dana is my fourth cousin with most recent common ancestral
couple Hugh Clancy and Marcella Blackall.
- My Clancy ancestors and the Downes ancestors were near
neighbours in County Clare.
- Three quarters of Dana's family tree was very complete, but
grandfather Raymond came to foster parents in Texas on an orphan train
in 1904 or 1905.
- Raymond's birth parents were known to be called Henry
Clancy and Catherine
Down(e)s and he used his mother's maiden surname.
- Cath Downes sailed on the Teutonic from
Queenstown on 21
September 1899 (line 22).
- Hewry [sic in transcript] Clancy sailed
the Lucania from Queenstown on 31 December
1899 (also line 22).
- Raymond was born in Manhattan on 24 January 1900.
- In the census of June 1900:
Downs (white, male, b. Jan 1900) was an Inmate in
the New York Foundling Asylum at 175 East 68 St. in New York (line 72).
Downs (white, female, b. May 1880 in New York [sic]
York [sic] born parents) was an Inmate and nurse also in the New York
Foundling Asylum (line 91).
Clancy (b. Apr 1874 in Ireland to Irish parents,
migrated 1899, 6/12 year in United States, alien, Car blacksmith) was a
boarder with the Haley family at 512 Spruce Street in the 9th Ward of
Terre Haute City in Harrison Township in Indiana (line 68).
- Henry Clancy travelled to New York especially to finally marry Catherine Downes on 2
- Their daughter Margaret Clancy (18 July 1905-26 December
1994) never married.
- Did she know that she had a full brother in Texas?
Conclusion: 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
Irish people to submit
DNA samples to the databases for purely genealogical purposes.
- Your 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 various websites.