An AncestryDNA test reads 700,000 genetic markers from a saliva sample to estimate your ethnic origins and find DNA matches.
You spit in a tube, mail it off, and weeks later a breakdown of your ethnic origins appears online. The process behind how the Ancestry DNA test works is simpler than the science sounds, and knowing what happens at each step helps you read your results the right way.
The Science Behind The Spit Sample
AncestryDNA analyzes autosomal DNA, the genetic material you inherit from both parents. This gives a broad view of your ancestry across all your family lines, unlike tests that only trace one parent’s side.
The lab looks for single nucleotide polymorphisms, or SNPs, which are single points in your DNA where people commonly differ. Ancestry’s chip reads 700,000 of these markers from your sample, then compares your patterns against reference populations to estimate where your ancestors likely came from.
The 5-Step Process From Kit To Results
Each step in the Ancestry DNA test workflow matters, and skipping one stops the whole process.
- Order and receive your kit in the mail.
- Activate the kit online using the code inside. The lab cannot process an unregistered sample, so this step is mandatory.
- Provide a saliva sample by spitting into the tube to the fill line, capping it, and sealing it in the provided bag.
- Mail the sample to Ancestry’s lab in the prepaid envelope.
- Receive your results online when processing finishes, typically within 6 weeks of the lab receiving your sample.
If the lab cannot read at least 98% of the SNPs tested, no results are issued. Too little saliva, or a sample contaminated by food or drink, is the most common reason a test fails.
What Your Results Actually Tell You
Your results arrive in two main parts: an ethnicity estimate and DNA matches. Think of them as clues, not proof of exact nationality.
The ethnicity estimate assigns percentages of your DNA to regions like “England & Northwestern Europe” or “Nigeria” based on how closely your markers resemble reference populations. Ancestry compares your data against population data from 2,600+ regions worldwide, working from a matches database that holds over 25 million DNA test takers.
DNA matches show people in that database who share DNA segments with you, indicating a likely family relationship. Ancestry also identifies genetic communities, which are groups of people who share ancestry from a specific place or migration pattern, and can add family-history context.
Here is what the different results translate to in practice:
| Result Type | What It Shows | How To Use It |
|---|---|---|
| Ethnicity Estimate | Percentage breakdown of origins by region | Broad clue, not exact nationality |
| DNA Matches | Likely relatives in the database | Build family trees and contact matches |
| Genetic Communities | Groups sharing ancestry from one region | Adds historical migration context |
MedlinePlus and the National Institute of Standards and Technology both note that these tests provide probabilistic estimates based on reference databases, not historical certainty. A 30% estimate for one region does not mean one of your grandparents was entirely from there. Results can also shift as Ancestry updates its reference panels and algorithms.
Before you order, review Ancestry’s data-sharing and privacy settings. Taking a DNA test reveals information about you and any biological relatives, so knowing how your data is handled matters. If you are comparing options, our roundup of the best DNA ancestry tests breaks down how each service compares on markers, database size, and cost.
FAQs
How long does AncestryDNA take to deliver results?
Ancestry states results are expected within 6 weeks of the lab receiving your saliva sample. Shipping time to the lab adds a few days on top of that, so plan for roughly 6 to 8 weeks from mailing the kit to seeing results online.
Why did my ancestry results change from last year?
Ancestry periodically updates its reference populations and algorithms. As the database of 2,600+ regions grows and improves, your segments may be assigned to different regions, shifting your percentages. Your DNA did not change, but the comparison set did.
Can an AncestryDNA test identify a specific ancestor?
No. The test estimates which populations your DNA segments resemble, and it cannot pinpoint a single verified ancestor. DNA matches can help you build a family tree and confirm relationships, but the ethnicity estimate alone is a probabilistic clue, not a genealogical record.
References & Sources
- Ancestry. “How Does AncestryDNA Work?” Details the 700,000 markers read, the 2,600+ reference regions, kit activation, and the 98% SNP quality threshold.
- National Institute of Standards and Technology. “How Do Companies Measure DNA To Discover Your Ancestry?” Explains SNP-based testing and the probabilistic nature of ancestry estimates.
- MedlinePlus. “What Is Ancestry Testing?” Clarifies what results can and cannot tell you about your genetic history.