Notes on DNA testing
for family history research
by
Trevor Rix
For anyone that has not encountered family
history DNA before it is all rather mind boggling and bewildering. That's how
it was for me until I started investigating last year. I will try to summarise the benefits and the disadvantages, and address
some questions that have been raised.
Why should we consider
DNA testing for family history research?
Y-DNA only passes down the male line from
father to son. Females do not have any Y-DNA.
Y-DNA tests only a few specific markers on
the 23rd chromosome that are passed down through the generations over thousands
of years from father to son to son etc., and that are useful for family history
purposes. Only males have Y-DNA and can take the Y-DNA test. This test is
therefore beneficial to one-name studies such as the Barcham (and variants)
study where both the surname and the Y-DNA is passed
more or less intact down the male line. All male descendants through the male
line have essentially the same DNA (but see mutations below). The main benefit
is to discover whether the various lines of Barcham from the inception of the
use of the surname Barcham (and variants), most likely from the 1200-1400 AD
timeframe, all descend from the same stock or from multiple roots. It follows
that the technique is used to allocate testees into
groups. The groups may stay independent of each other or may be proved to have
a common ancestor at some point in time.
What benefit might
there be to the Barcham Family?
If a Barcham and a Burcham
(or any present-day variant) take the test and there is an exact or close match
on the Y-DNA it is extremely likely that they both descend from the same person
even if that person lived way back in 1300. It may have been impossible to
establish that link using traditional family history research through
documents. That is a major benefit.
Furthermore these people are likely to have
close matches to people that do not have the surname Barcham (or variants) in
which case the common ancestor is likely to have been before the use of
surnames became commonplace in the 1200-1400s.
Most Y-DNA markers mutate very slowly over
the centuries. By studying the few mutations that do occur
it is possible to estimate how long ago two people were related (known as the
Most Recent Common Ancestor). Two people may be related only a few generations
back, or the common ancestor may have been centuries ago.
The extensive Barcham records going back to
the 1600s can therefore in theory be pushed backwards in time over many
centuries using Y-DNA testing.
Who would carry out
the tests?
The company, Family Tree DNA (FTDNA), undertake
most of this interpretation and evaluation as part of their service. It is all
built into the initial cost of taking a test. There are tools on the FTDNA
website that compute the matches with other people and the timescales involved.
No one needs to be a biochemist. It is already a well established refined
science. So far there are 4502 different surname projects on the FTDNA website.
FTDNA also compute the broad geographic
origins of people being tested. People are assigned a haplogroup
that defines the part of the world that the person's male line ancestors
originate from. It is thought that all people have migrated over time from
What qualifications
does the administrator need and who would be tested ?
The proposed surname project administrator
(Barcham volunteer) does not have to be a geneticist but would need to know
enough of the basics however to decide which people it would be most beneficial
and cost effective to test. The people that take the test would be expected to
be interested enough to pay for the whole of the cost of their test themselves.
It is only if a key person is identified who is unwilling to pay the cost
himself that any Barcham funds would be used to partially subsidise
the test. That's how it usually works, assuming that people are willing to be
tested in the first place which is not always the case.
What does it cost?
The minimum cost of a Y-DNA test is the
group discount rate of US$99 (about £50) for a test on the first 12 markers.
For myself I decided to take the more comprehensive 67 marker test (and also a mtDNA test — more on that later)
for a total of £206. I hear gasps all round, but tens of thousands of family
historians around the world have already paid that sort of money to be tested.
I am proposing that some Barcham funds be eked out over many tests over many
years to subsidise important tests.
As females do not have any Y-DNA and cannot
be tested, it is very common for females to pay for their father or brother or
a close male cousin to take a Y-DNA test on their behalf.
Would we have to
obtain DNA from the graves of our ancestors?
The test is on living people, not ancestors
in graves. As the results of the tests are so revealing and accurate it is not
necessary to test dead people at all.
Are there any
disadvantages to consider?
The big disadvantage is if someone's Y-DNA
results reveal what is known as a non-paternal event; that is where a presumed
father somewhere along the line is not the biological father. If that prospect
is too disturbing for a person to contemplate then they should not take the
test. Most people are however realistic and would rather know about such an
event than waste years of their lives and a large sums of money tracing a line
that is nothing to do with them biologically.
Can females be
tested too?
Mitochondrial DNA (mtDNA)
only passes down the female line from mother to children. Everyone can
therefore test for mtDNA. Only females can however
pass on their mtDNA to the next generation. mtDNA testing is less useful to a
surname study such as Barcham because surnames are not normally passed down the
female line from mother to daughter to daughter.
It is interesting to note that my mother's,
mother's, mother's, mother's, mother was Elizabeth
Thompson who married Ezra Barcham in 1818. My mtDNA
test results will therefore be identical to the results of Elizabeth Thompson.
That is why it is not necessary to test dead people.
mtDNA mutates extremely
slowly and is so persistent that the results are highly accurate in determining
the geographic origins of female ancestors in the strict female line over
thousands of years.
What can DNA testing
tell us about our ethnic origins?
Everyone male and female has autosomnal DNA
which is a big mix of DNA passed down from all of one's ancestors. The catch is
that the mix is completely random which is why this type of DNA testing is
regarded as being only of interest rather than being of much practical use. For
example I may have a mix of exactly 25% of the autosomnal DNA from each of my
four grandparents. However my autosomnal DNA may be 100% from only one of my
four grandparents and none from the other three. The truth lies somewhere
between those two extremes. Nevertheless it is possible to calculate the
theoretical most likely mix of the geographic origins of all of one's
ancestors. That is how family history TV programmes
calculate that someone is for example 32% Jamaican.
If anyone has read down as far as this I say well done and thank you for your
time! I think Judith's suggestion to conduct a debate on the 'Barcham blog' is a very good one.