Back in 2015, my cousin Jim Sherlock suggested that I should take an autosomal DNA test. His son had purchased a test for him through 23andMe and Jim thought that it was a great genealogical research tool.
An autosomal DNA test does not identify the paternal or maternal ancestral lines, but identifies any segments on all 23 chromosomes of your DNA that match with segments of other people who have tested. In general, the higher the percentage of shared DNA, the closer the relationship, but the amount shared is not a straight mathematical calculation, as which segments you get from your father versus mother are random, so the possible range of shared DNA increases with each generation.
Blaine Bettinger provides a very handy chart on his The Genetic Genealogist blog, that shows the anticipated amount of shared autosomal DNA with each successive generation; In general terms siblings share on average about 50%; 1st cousins about 12.5%; 2nd cousins about 3.125%; etc. This represents roughly 3400 centiMorgans (cM), 850 cM, and 212 cM respectively. But at the 2nd cousin level, the amount shared may vary from 43-504 cM, so quite a wide range.
I did my own research, comparing the big 3 North American testing companies (23andMe, Ancestry DNA and Family Tree DNA), and decided that 23andMe would give us the best overall value on health and ancestral information. So I promptly ordered kits for myself and Marlene, submitted the saliva samples and waited for the results.
The health information did not identify any real concerns, and Marlene was somewhat amused to learn that I have 2.6% Neanderthal DNA, but she has only 2.5%. She thinks that she is therefore more evolved than I am.
But my real interest was in the ancestral information, of which there was an abundance. A speculative view tells me that I am 99.8% European, with the most significant portion being British / Irish at 92.5%. This was not too surprising, considering that I have not identified any non-European ancestors to date, going back at least 6 generations. The 2.6% Scandinavian and 0.1% Ashkenazi Jewish were news to me, and I hope at some point that I can determine which ancestral lines include these populations.
My cousin, Jim Sherlock, is identified as sharing 12% DNA with me in total, which is a good reference point, as we already know that we are 1st cousins. But beyond Jim, the next closest match shared about 0.5% of my DNA, and is suggested to be a 3rd to 4th cousin. Of course none of my closest matches had pedigrees that took them back far enough to establish a relationship to my ancestors, so I was somewhat disappointed.
Marlene's matches were somewhat more fruitful, and we were very quickly able to break through a brick wall on her LeBlanc line and can now take it back fairly reliably to the 1600s in Acadia (present day Nova Scotia).
Over the following 12 months, many more people took the test and appeared in our list of matches, and I now have a first cousin once removed with 6.84% shared and a second cousin once removed with whom I share 1% DNA.
We have been introduced (electronically) to many new cousins, some with very interesting family stories, but I was afraid that we were missing out, not being able to compare our DNA with people who had tested with other companies, so we uploaded our DNA results to GEDmatch.com, which I will discuss in a subsequent post.