A few years back I took an autosomal DNA test both with Ancestry and with Family Tree DNA. 

An autosomal DNA test will test both your maternal and paternal ancestral lines back to 5, maybe 6, generations. You inherit about 50% of this type of DNA from your mom and 50% from your dad, so your autosomal DNA gets ever more randomly shuffled from your ever more distant ancestors and, therefore, diluted with each generation. The results you get from this type of DNA will estimate to what degree you are related to someone else in the database, e.g. you get matched at 1st to 2nd cousin level, or 2nd to 3rd cousin, or 4th to 6th cousin, etc.

My great-great grandfather on my paternal grandfather’s side was Nicholas Neil who lived in Carrawaystick in Glenmalure in County Wicklow (Ireland). Hillwalkers will be very familiar with Carrawaystick Waterfall. The zigzags by the waterfall were originally a path used as a hunting trail by the family of Charles Stuart Parnell, who were based in nearby Avondale. My ancestor, Nicholas Neil, was recorded along with a Henry Neil in the townland of Carrawaystick on Griffith’s Valuation, a mid-19 th century property valuation for taxation purposes.  

As a result of my DNA tests, a lady contacted me to say that she is a 4th cousin match. It appears that her great grandmother was a daughter of Henry Neil (her great-great grandfather). If the match is an exact 4th cousin (i.e. the ancestor we share in common is a great-great-great grandparent), then the Henry Neil and Nicholas Neil listed on Griffith’s Valuation must be brothers. Griffith’s Valuation took on a new meaning to me after making that discovery. Not only do I have a genealogical connection to Nicholas, I now know that I also have a DNA connection, and that I can talk by e-mail to a descendent of my great-great granduncle.

The amount of autosomal DNA from a distant ancestor (more than 5 generations) can be so diluted as to not be detectable. This means that autosomal DNA cannot answer family history questions the further back than about 5 or 6 generations in your ancestral lines. But for less than 6 generations … it genuinely can help!

By Maura Flood