Probably best if I paste a section of my Building a Family Tree file that I produced for my first Cousins who are interested in our family history and they have supplied valuable information.
I would concentrate just on Ancestry to work through the Common Matches, then look at linking to the high cM matches who do not as yet have a known Common Ancestor(s).
I would also upload Raw DNA to Gedmatch, once it has complete its search then I suggest learning how to use each of the free tools after watching the linked video tutorials that there are in each of the tool section.
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DNA TESTING AND MATCHING.
Buy an Ancestry DNA test(s) when they are on offer at a reduced price. If you can get your older family members to take a test as they will have much more DNA to potentially more distant matches than you will.
Once the test results are known the next step is to link them in your Ancestry Family Tree to the person whose DNA test it is. You can have multiple people within your Tree tested and each will need to be linked to the family member concerned within the tree, but you can only link each test to a person within one specific tree.
It can take a few days for the worldwide database to be scanned and DNA matches reported to your online Ancestry Account.
The DNA section of the Ancestry website is split into three, Ethnicity, DNA matches and Thrulines.
Ethnicity, gives an approximate estimate of the Countries/Regions where percentiles of your DNA breakdown are likely to originate from. The estimate is based on the locations and locations or trees if available of all the people who have taken a test. The result is the Ethnicity changes, ours bears little similarity to what it did originally.
DNA Matches, is the prime section where all the matches are displayed. Select the person whose sample it is and the matches are displayed in order of the size of the cM match to them. cM is the centimorgan measure of the DNA tested. You have about 7400 cM of DNA of which half is from each parent. You share about 1500 cM with each Grandparent, 900 cM with a Cousin, 450 with a second or 1/2 Cousin etc
Thrulines, are links from specific ancestors to the DNA matches who share that person with you. Click on your Ancestors to view the suggested links.
A new section is Ethnicity Inheritance and is a guesstimate as to which parent has supplied the various aspects of your ethnicity.
DNA MATCHES, WHAT NEXT.
Select the DNA MATCHES and view the listings, the first ones to look at are those where Common Ancestors is displayed since Ancestry has created a route from the DNA Match to the Person in your Tree whose matches you are reviewing. Note that these are not necessarily from a single tree, they are compiled from multiple Trees. Hence care is needed to verify each individual, generation by generation as you add them to your tree.
Additional actions once a link is created to a DNA match is to use the Filters and give them a Star, this in future makes it easy to apply the Filter to only display the Star matches who are proven and linked family members. You will find that a note can be added, I add the names of the common grandparents a “ - “ and then the full birth name of the DNA match.
Once all the DNA matches with the Common Ancestor displayed have been added to your tree the remaining matches with the highest cM value but no Common Ancestor is the one to investigate next. Then continue working down the list.
There can be a good deal of frustration, ie very odd user names and no tree, trees with few people included within them, extensive trees that contain no identifiable surname that you have in your tree and unlinked trees so you have no exact idea which is your actual DNA match.
The lower the cM the further back in time it will be before a common ancestor and hence a temporary cutoff for your research of 50 cM is practicable.
Now go back to your highest cM that you have linked to and look at their shared matches, this will indicate that the unlinked ones displaced share the same family line but not necessarily the same common ancestor as your linked match. You can use this information to investigate each shared match.
My own process for the unlinked high cM matches is to create my own tree specifically from them (standalone and hence not a floating unlinked part of my own tree), this tree can be imported into your own Family Tree software when you find the common ancestor.
So now you have a very extensive Family Tree with as many DNA matches linked within your tree as is practicable and you can return to extending your tree back by further generations searching for that elusive Gateway Ancestor if that is a desire.