Thursday, 30 January 2014

Finding distant cousins using autosomal DNA

If you're close minded about anything new, so enamored with Y-DNA you can see no further, or get turned off by statistics you should probably leave this post right now.

If you'r still with me open up to the possibilities of autosomal DNA testing which, at its most elementary, allows you to confirm the biological reality of close relationships.
For more distant relationships the often quoted statistics, that with an autosomal test, on average, you have a 90% of matching a 3rd cousin, 50% for a 4th and 10% for a 5th cousin deter many from probing further.

Yet chances are you have substantial segments of DNA in common with more distant cousins, the probability is small but we have many more of such distant cousins. It's a matter of chance.

Kitty Cooper's Blog recently carried the story of her match, a bit under 10 cM on chromosome 16, with two people, 6th and 9th cousins. They were of Norwegian origin and she was fortunate enough to find the matches had good ancestral research.

Unfortunately while DNA provides the evidence, the clue that a connection exists and an idea of the closeness of the relationship, it's not exact. Kitty, who shows up as third to distant cousin on my 23andMe match list, points out in a post on the 23andMe Community that "any two Ashkenazi Jewish participants in the study shared about as much DNA as fourth or fifth cousins."

Maybe one day we'll be able to genetically engrave a family tree in our DNA to be passed along to descendants.

1 comment:

Anonymous said...

Anne in Ottawa says
" A dna relative(likely 4th cousinish) tells me her Mennonite husband has 108 2nd cousin matches, due to much intermarriage in that group."
As John says, the autosomal test confirms a relationship we know, but also gives a comparison to others. One first cousin relationship in my family shares 1000 units; another only 758 units (i.e centimorgans, the unit of measurement for autosomal dna) The more distant matches can help us piece together some of the ancestry puzzle and at the very least give us some contacts/connections of interest. Lastly, it is a waiting game as more people are being tested all the time.
Thank you John for leading the interest in this area.