DNA and genetic genealogy offer an alternative means to physical library and parish church records of confirming relationships. Although the principles of genetics and DNA have been used for many years to establish relationships between people born centuries apart, it is only recently that it has been available to the general public. If no conventional source is available to connect a familial link, genetic testing can.
Even if an ancestry DNA test cannot establish a direct relationship, it can still determine whether two DNA sources share or shared a specific group, such if they were Jewish or African in ancestry. The genetic differences that make one person unique from every other person lie in only 0.1% of their DNA, and if people share the same 0.1% mutation in their DNA, then they would definitely have had a common ancestor somewhere down the line.
How far down the line depends on the mutation, and scientists have now identified what are known as ‘genetic markers’ that determine a common genetic ancestry. Thus, a DNA test cannot just be used to determine beyond reasonable doubt that a certain person is your father, but if taken from a more ancient source, can determine if you are related to that person.
DNA and genetic genealogy can tell you about direct descendency, from father to father to father, or mother to mother, but cannot be too precise regarding collateral ancestry, or aunts, uncles and so on that are not in your direct line of ancestry. However, you can pair genetic genealogy with tradition methods of ancestry research to fill in the blanks so that there is little doubt about the matter.
It is not the purpose here to explain how genetic genealogy works, only to state that it does work, and that the technique can be used to fill in blanks in your family tree or to confirm a relationship that was hitherto in doubt. DNA testing is now available to the public, and you can pay to have two samples tested to determine the relationship between them. In many cases it is possible to determine by roughly how many years the relationship is separated.
Ancestry Testing for Maternal Lineage
Although DNA genealogy is largely connected with paternal relationship, the mothers are not left out. Maternal DNA, or mitochondrial DNA, is passed from mothers to their children, although it is purely a female-line DNA strand, and is passed from mothers to daughters to their children, but not from sons to their children. Tracing maternal lineage can be done by this MtDNA. Both male and female can therefore be used to determine relationships separate by large time gaps, though male DNA offers most information.
There is also a type of DNA known as autosomal DNA that is passed down both genders and can be used to determine relationships down all family lines and therefore of use specifically for female relationships that hitherto were weak. It can be used to determine whether a child is the grand-daughter of an assumed grandmother, and the relationship can be taken even farther down the direct genetic line.
By carrying out DNA and genetic genealogy it is possible for people with the same family names to determine whether or not they are related. If so, then imagine how useful that would be if you were building a family tree and they were also! You could combine your family trees to produce an extended tree that may ultimately join you both up.
That is one of the powerful uses of DNA in genealogy, and there are many more. If you are able to get DNA samples from ancient remains you can establish a relationship with them if there is one, and the tests can even be used to determine the time gap between relationships.
DNA and genetic genealogy has just made ancestry research much more interesting and provides you with an opportunity to back up the results of your research with some hard indisputable evidence.