DNA and Family History

From the files of Stephen M. Lawson

DNA analysis is rapidly becoming an exciting and important aid to genealogical research. Note that, thus far, DNA research is only an aid to family history. A complete match of Y-DNA between two males, for example, only indicates that it is highly probable that they have a common ancestor in the patrilineal line - it does not identify the common ancestor, nor does it indicate the specific number of generations back in time that the ancestor lived.

However, that said, DNA analysis can aid in several ways. First, if two persons with identical DNA have traced their ancestry by paper trail to a common ancestor, the DNA results supports the lineages. Second, if these same two persons have DNA that does not match (by multiple markers), it indicates that there is a break in the supposed lineage of one (or both) of the lines (perhaps there was a previously unrevealed adoption). Third, and perhaps most exciting, is that a common DNA between two persons who did not know of a common ancestor gives significant clues for further research to locate the common ancestor.

There are two kinds of DNA analysis of interest in family history: Y-DNA follows the male line only, and mt-DNA (Mitochondrial DNA) follows the female line only. A son has the Y-DNA and mt-DNA of his parents, but a daughter only has the mt-DNA of her mother. The male passes on the Y-DNA only to sons; the female passes on the mt-DNA to both sons and daughters.

DNA genetics is a complex field. There are a number of web sites that provide extensive information, such as the DNA 101 section at FamilyTreeDNA.com . The New England Ancestors magazine of the New England Historic Genealogical Society has had a very informative column "Genetics & Genealogy" since the Fall 2002 issue (Vol. 3, No. 4) - 16 case studies through 2005.

I - The I, I1, and I1a lineages are nearly completely restricted to northwestern Europe. These would most likely have been common within Viking populations. One lineage of this group extends down into central Europe.

R1b - Haplogroup R1b is the most common haplogroup in European populations. It is believed to have expanded throughout Europe as humans re-colonized after the last glacial maximum 10-12 thousand years ago. This lineage is also the haplogroup containing the Atlantic modal haplotype.

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Modified: 8/11/08