The Pros and Cons of Mirror Trees



A mirror tree is a tool that some genealogists use in order to discover more relatives that are DNA matches. A genealogist starts with his or her own family tree and then makes a mirror image of the family tree of a cousin. Here is a quick look at some of the pros and cons of mirror trees.

A mirror tree is a direct copy of a family tree. The mirror might be of the entire tree, a certain line in the tree, or a tree of someone who is one of your DNA matches.

A genealogist who takes an AncestryDNA test will be presented with “Shared Ancestor Hints”. In short, these hints point at people whom the genealogist shares some DNA. The purpose of a mirror tree is to “trick” Ancestry’s algorithm into providing additional “Shared Ancestor Hints” that a genealogist had not already been given.

To make a mirror tree, a genealogist starts by taking the AncestryDNA test. Next, create a family tree on Ancestry.com. Then, the genealogist selects a person that is a close DNA cousin – and who has a family tree that is linked to their DNA – and makes a mirror of that person’s family tree. The genealogist then links his or her own DNA to the mirror tree.

Pros of making a mirror tree:

  • It might help an adoptee to discover more of their biological relatives.

  • It might help a person searching for a long, lost, relative to find him or her.

  • There is potential that the genealogist will get more “Shared Ancestor Hints” via the mirror tree.

  • It gives you a second tree to work on, and make mistakes on, without messing up your own tree.

  • It is possible to make a mirror tree private – to prevent other genealogists from seeing it.

Cons of making a mirror tree:

  • A relative’s tree may have mistakes that cause the mirror tree to be inaccurate. This could lead to “Shared Ancestor Hints” that are not relevant.

  • A mirror tree starts with a falsehood – the wrong DNA has been attached to it. Other genealogists who come across a mirror tree won’t necessarily know it is a mirror. This could lead to the spread of inaccurate information.

  • The mirror tree may be unnecessary, especially for genealogists who have already done a great deal of careful research before including someone in their family tree.

Related Articles at FamilyTree.com:

* Tips for Discovering Biological Family with AncestryDNA

* AncestryDNA Introduces Genetic Communities

* Make Copies of What You Post on Ancestry.com

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