Ralls - Rawls DNA Project
This discusses in a general way what sort of information can be gained
from a Y-DNA test for genealogical purposes, as well as the limitations of
what the tests can tell us.
One obvious answer gleaned from a Y-DNA test is what we learn from a
non-match of test results—that individuals who do not match are not related.
When "paternity" is not well defined, anyone using DNA testing should be
aware of the possibility of unexpected non-matches, especially when dealing
with research going back many generations.
When test results do indicate a match, we then have to look-at the number of
"markers" or locations on the Y chromosome that were tested and compared.
The greater the number of markers tested, the smaller the range of
generations within which the common ancestor is likely to be found.
Currently, FTDNA offers 12 marker, 25 marker, 37 and 67 marker tests. The 25
marker test was introduced about 2-3 years ago, and the 37 marker and 67
marker tests have become available more recently.
For purposes of any meaningful genealogical information, the 12 marker test
is of almost no use other that to indicate with certainty that individuals
who do not match are not related. If a 12/12 match occurs, the range of
generations for finding the common ancestor is too wide to be of use in
genealogical research.
The 25 marker test can narrow the time span some-what, but it is our opinion
that since the 37 and 67 marker tests are now available, the narrower time
range it affords makes them the most logical choice for anyone hoping to
gain the most information from the Y-DNA test.
What the 25 marker test can tell us (and the 37 marker test to a finer
degree and the 67 to a much finer degree) is the Time to the Most Recent
Common Ancestor (TMRCA) of two individuals whose test results indicate they
are related. When we say "time", we are really speaking of a range of
generations and probabilities of accuracy. The test is not able to say, in
and of itself, that you and cousin "X" are related say, precisely 10
generations ago, or at some point say, exactly 173 years in the past. What
it can provide is a range of number of generations in which to look for a
common ancestor using traditional genealogical research methods.
DNA testing is not meant to be a substitute for genealogical research. DNA
testing, combined with your research, is an effective tool to resolve
unanswered questions, determine relatedness, identify research problems, and
to prove or disprove theories or research.
What kind of information is gleaned from a Y-DNA test and what steps are
taken to provide a measure of privacy for the individual providing a DNA
sample.
When a DNA test is done by a law enforcement agency, the objective is to
have a DNA test result that is unique to an individual. This is achieved by
testing the "re-combined" genetic material, mentioned earlier, found on the
first 22 pairs of chromosomes.
The objective of DNA testing for genealogy is to test locations that are not
unique to an individual. In the case of the Y-DNA test, several locations on
the Y chromosome are tested that remain virtually unchanged from father to
son. If several males were tested who had a common male ancestor, their Y
chromosome Genetic Genealogy test results would match or be a close match.
Therefore, this type of test does not identify an individual, rather a
lineage. We would like to emphasize this point: there is nothing in the test
results of an individual's Y-DNA test results that would identify him as a
unique individual.
The objectives of DNA testing for law enforcement and DNA testing for
genealogy are at opposite ends of the spectrum. The objective of Genetic
Genealogy is to find all those who match, and therefore had a common
ancestor. The objective of DNA testing for law enforcement is to identify a
unique individual.
As for the privacy of the test results themselves, the testing firm we are
using, Family Tree DNA (FTDNA), has a strict policy for protecting test
results. The actual DNA samples are sent to a lab identified only by a
number, not a name. The lab has no information about the sample other than
this number. FTDNA releases the test results only to the individual and, if
they have signed a release, to the surname project administrator.
At the “Ralls – Rawls DNA Project” there is an additional information
release form that all participants are asked to complete. The Information
Release form allows participants to specifically identify what information
they would like to make available publicly on the Ralls – Rawls
DNA Project web site.