Genealogy Basics
Which DNA Test Should You Take for Family History?
DNA testing has changed family history research, but only if you take the right test and use it the right way. The most important part isn't the ethnicity pie chart. It's the list of relatives you match.
The three kinds of DNA test
| Test | What it follows | Who can take it | Best for |
|---|---|---|---|
| Autosomal | DNA from all your ancestors, mixed together | Anyone | Finding cousins on every line from roughly the last five or six generations |
| Y-DNA | Your father's father's father's line only | Men only (the Y chromosome passes from father to son) | Surname studies; a direct paternal line many generations back |
| Mitochondrial (mtDNA) | Your mother's mother's mother's line only | Anyone | A direct maternal line; very deep ancestry, but matches are often too distant to be useful |
Which test to take first
Start with an autosomal test. It's what most people mean by "a DNA test," and it's the most useful for genealogy because it finds relatives through all your family lines, not just one.
Each company compares you only with the people who tested with that company, so the size of the database matters more than anything else. AncestryDNA has the largest database and is the usual first choice for people researching U.S. families. 23andMe, MyHeritage and FamilyTreeDNA also offer autosomal tests. Some companies let you upload results you've already got from another company, which can find more matches without testing again.
Y-DNA and mitochondrial tests are specialized tools. FamilyTreeDNA is the main company for both. They're worth adding later to answer a specific question about a direct paternal or maternal line.
Matches matter more than ethnicity estimates
Ethnicity estimates are fun, but they're estimates. They change as companies update their reference data, and they rarely answer a genealogy question.
Your match list is where the research happens. For each match, the company shows how much DNA you share and suggests a relationship. Then you look for:
- Shared surnames and places in your match's family tree
- Shared matches, people who match both of you, which help sort matches into family lines
- Matches with good trees, where you can work out the common ancestor
Who in the family should test
- The oldest generation first. A grandparent's DNA is one generation closer to your ancestors and finds matches yours may not.
- Both sides. If one parent is living, testing them shows which side each of your matches comes from.
- A direct-line male for Y-DNA questions about a surname line.
Before you test: privacy and surprises
- Read the privacy settings. You can usually choose whether you appear in match lists and whether your data is used for research.
- Think about who else is affected. Your DNA is shared with your relatives.
- Be ready for surprises. DNA sometimes reveals unknown siblings, adoptions or different biological parents. Many people find this meaningful; it can also be hard. Go in knowing it's possible.
Use DNA with the records, not instead of them
DNA tells you that you're related to someone. Records tell you how. The strongest conclusions use both. A DNA match plus a census record, a will or a family Bible that points to the same ancestor is far more convincing than either alone.
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