What Is DNA Ancestry Testing?

DNA ancestry testing analyses a sample of your saliva to identify genetic markers inherited from your ancestors. These markers are compared against large reference databases to estimate your ethnic origins and identify biological relatives who have also tested. It is one of the most powerful tools available to modern genealogists — but it works best when combined with traditional documentary research.

The Main Types of DNA Tests

There are three core types of ancestry DNA tests, and each answers different genealogical questions:

  • Autosomal DNA (atDNA): Tests DNA inherited from both parents and covers roughly five to seven generations back. This is the most commonly used test and is offered by most major testing companies. It identifies cousins across all family lines.
  • Y-DNA: Passed directly from father to son, this test traces your direct paternal line far back in time — sometimes hundreds of generations. It is only available to biological males.
  • Mitochondrial DNA (mtDNA): Passed from mothers to all their children, this test traces your direct maternal line deep into the past and can reveal ancient migration patterns.

Choosing a Testing Company

The major consumer DNA testing services each have different strengths. When choosing, consider the following factors:

  1. Database size: A larger database means more potential DNA matches and relatives to connect with. Larger databases generally produce more useful cousin matches.
  2. Ethnicity reference panels: Each company uses different reference populations. Results can vary — sometimes significantly — between providers.
  3. Tools and features: Look for chromosome browsers, shared match tools, and family tree integration, as these help you make sense of your matches.
  4. Privacy policies: Understand how your DNA data is stored, shared, and used before you test.

Understanding Your Ethnicity Estimate

Your ethnicity estimate is exactly that — an estimate. It is based on statistical comparisons with modern reference populations and should not be read as a precise ancestral breakdown. Estimates can shift as companies update their reference panels. Treat your ethnicity results as a helpful starting point, not a definitive statement of identity.

Common surprises in results include unexpected regional breakdowns, the presence of small percentages from regions you were unaware of, and the absence of heritage you thought you had. These discrepancies often have logical explanations rooted in how DNA is inherited — not every ancestor passes detectable DNA to every descendant.

Using DNA Matches to Build Your Family Tree

The real genealogical value of DNA testing lies in your match list — the list of other testers who share DNA with you. Here is a basic workflow for making use of your matches:

  1. Focus first on your closest matches (parents, siblings, first and second cousins) to confirm known relationships.
  2. Look for matches who have public family trees attached to their profiles and identify common surnames or locations.
  3. Use "shared match" tools to cluster your matches into family groups, which helps narrow down which ancestral line a match belongs to.
  4. Reach out to matches with a polite, specific message explaining your research goal.
  5. Document every connection you make, noting the amount of DNA shared (measured in centimorgans) and the predicted relationship.

Combining DNA with Documentary Research

DNA evidence alone rarely tells a complete story. The most effective genealogists use DNA results alongside birth certificates, census records, church registers, and immigration documents. A DNA match can point you toward a family line; documentary records then help you identify the exact ancestor you share.

Getting Started

If you are new to DNA genealogy, the best first step is to test yourself and as many close relatives as possible — particularly older generations, as their DNA contains more genetic diversity from past generations. Parents, aunts, uncles, and grandparents are especially valuable testers. Once you have results in hand, explore the free educational resources offered by genealogy societies and online communities dedicated to genetic genealogy.