Your DNA Results

Those DNA "Cousin" Matches - What to Do with Them?

Autosomal DNA tests are referred to as cousin tests and are the most common DNA tests offered by companies such as MyHeritage, Family Tree DNA and Ancestry.  It's important to remember that the results represent your relationships to people on both your maternal and paternal lines.  The results will not show you from which side you received your DNA or where you share a relationship, only that you share some type of biological relationship at some point in time.

When you receive your results you will see a list of people with whom you share some amount of DNA. Remember that after 4 to 5 generations, expected relatives may not show up in your matches because we get differing amounts of DNA from each of our parents, and they from their parents and so on.  You may be surprised to find that you match with some cousins and not with others who are the same degree of biological relationship.  

The length of a piece of DNA is measured in centimorgans (cM). The total length of all your chromosomes combined is around 7400 cM. Since a person inherits about half of their DNA from each parent, you share about 3700 cM with each parent. The exact number for each parent/child relationship can vary slightly, but not by a lot.The more centimorgans (cM) you share with another person suggests the more recently you shared a common ancestor.  If the common ancestor is a great grandparent, (we had 8 of those), you could have received a varying amount of chromosomes from any one of those persons.  If the common ancestor we share is a great great grandparent, (we have 16 of those), the chromosomes could be from any of those people and in varying amounts.

Examples of Approximate Shared Centimorgans (cM) and recent relationships

1st cousins:  500 to 1000 cM received from at least one of 4 grandparents you share.

2nd cousins:  200 to  500 cM received from at least one of 8 great grandparents you share.  

3rd cousins:   85 to  200 cM received from at least one of 16 great great grandparents you share.

At the end of August 2020, Ancestry is curbing the number of matching results you will see.  If you share less than 8 cM with a person, you will not see those matches.  As you might guess, if you share less than 8 cM, your relationship was in the very distant past.

Unless a person has an extensive tree or you already know how you are related, there is little value in knowing that you have a small match (cM) with a person.  Families in remote locations tended to intermarry other families in the same area, so it's often difficult to even guess where the match occurred. Once in a while a small match has led me to a person's tree that might have clues to explore further, but I have enough to keep me busy for a lifetime with my other matches. 

When you get your results, you may be shocked to learn how many "cousins" you have.  For example, in Ancestry DNA, I have over 1000 matches who are 4th cousins or closer.  Depending on the number of generations between us and our common ancestor, a 4th cousin may share a great or great great grandparent with me. Because I am "older" and many tested are younger, there might be even more generations.

This is why family trees are so important to help sort the results.  If a person has not posted a tree with more than 2 or 3 generations, and your match is more distant, the results will be of no help in determining how you are related.  If there is no tree at all, the results are basically useless.  If you want to use your results to connect with others and to help complete your tree, add a tree and don't make it private. 

Screening your matches has been made easier by the added filters in Ancestry. The options are Unviewed - so as not to keep looking at the same matches; common ancestors-  which helps you see how Ancestry believes you are related; Messaged - identifies those you have contacted or contacted you; Notes-  are added by you; Trees-  indicate if there are trees and if they are public or private; Shared DNA allows you to enter the degree of relationship or the cM range to filter; and Groups - are color coded manual sorts that you have entered.  The option to select several filters is very helpful.  When I open my matches, I use  Unviewed and Common Ancestors i-for a quick helpful search of my matches.

There are 2 more options of Search and Sort.  If you select Search, for example, you can put in a surname and also a location of birth to search trees of people with whom you match.  I find this very helpful to narrow down people when there are many with the same surname.

Finally, in Ancestry you also have the option of managing the results of someone else who has been tested.  They retain their results, but they can also give you permission to view their results.  I have that option with some folks who share my birth name. 

DNA matches are a way to feel that you are on the right track for your ancestral line.  But remember, although you may match with another person  who has your ancestor in their tree, that might not be how you are related.  

DNA matches do not replace documentation.