Why Are My Ancestry and MyHeritage Results So Different?

If you’ve taken DNA tests from both Ancestry and MyHeritage and are scratching your head at the discrepancies, you're not alone. The most common reasons why your Ancestry and MyHeritage DNA results are different boil down to three primary factors: distinct reference populations, different algorithms for analyzing your DNA, and variations in the specific DNA markers they test. These differences, while sometimes leading to surprising variations, are largely a reflection of how each company approaches the complex science of genetic genealogy.

Understanding these nuances is key to interpreting your DNA results and appreciating the unique insights each service can offer. It’s not necessarily that one is “right” and the other is “wrong,” but rather that they are providing different perspectives based on their methodologies.

The Science Behind the Splits: Understanding DNA Testing Companies

Embarking on the journey of genetic genealogy is an exciting adventure, often spurred by the desire to uncover family history, connect with distant relatives, or simply understand where you come from. Companies like AncestryDNA and MyHeritage have made this accessible to millions. However, when you receive seemingly contradictory results from different providers, it can be confusing. This article will break down why these differences occur, what they mean for your genealogical research, and how you can make sense of the information you receive.

Key Takeaways for Understanding Differences in DNA Results:

Reference Populations: Different databases of existing DNA profiles used for comparison.
Algorithms: Unique computational methods for interpreting your DNA data and assigning ethnic origins.
DNA Markers Tested: Variations in the specific locations on your DNA that each company analyzes.
Immigration Patterns: How historical migration and the resulting genetic makeup of regions influence results.
Data Updates: How companies periodically refresh their reference populations and algorithms.
Paternal vs. Maternal DNA: How some tests focus on specific lines, while others are broader.
Genetic Ancestry vs. Paper Trails: The distinction between what your DNA suggests and what historical records show.

1. The Cornerstone of Difference: Reference Populations

One of the most significant factors contributing to the differences in your AncestryDNA and MyHeritage results lies in their reference populations. Think of a reference population as a meticulously curated collection of DNA samples from individuals whose ancestors have lived in a particular geographic region for many generations. When you submit your DNA, these companies compare your genetic makeup to these reference panels to estimate your ethnic percentages.

Why this matters:

AncestryDNA's Global Reach: AncestryDNA boasts a vast and diverse reference population, drawing heavily from North America and Europe. Their panel is particularly strong in representing populations with significant historical immigration to the United States. This means if your ancestors have a long history in the U.S., or came from regions that heavily contributed to American demographics, AncestryDNA's results might feel more precise.
MyHeritage's European Strength: MyHeritage, with its strong roots in Europe, has a particularly robust reference population for European countries. They excel in identifying detailed regional origins within Europe, such as specific areas in England, Ireland, Germany, Scandinavia, and Eastern Europe. If your ancestry is primarily European, MyHeritage might offer more granular insights into those regions.
The "Iberian Peninsula" Example: For instance, MyHeritage might break down your ancestry into specific regions within Spain and Portugal, while AncestryDNA might assign a broader "Iberian Peninsula" percentage, or even combine it with other Southern European groups. This isn't necessarily an error; it's a reflection of the granularity and focus of their reference panels.
Underrepresented Ancestries: If your ancestry includes populations that are less represented in the global DNA databases (e.g., certain indigenous groups in South America, specific populations in Africa or Asia), you might see more significant variations or broader estimations from both companies.

In essence, the results you get are a comparison to the best available data. If your DNA shows a strong match with a reference group that one company has detailed, and another company has a broader or less detailed group for that same ancestry, the percentages will naturally diverge.

2. The Magic Behind the Numbers: Algorithms and Methodologies

Beyond the reference populations, the algorithms that AncestryDNA and MyHeritage use to interpret your DNA data play a crucial role in shaping your ethnic estimates. These are complex computer programs designed to analyze millions of data points in your DNA and assign them to specific ancestral groups.

How algorithms contribute to differences:

Different Analytical Approaches: Each company has developed its own proprietary algorithms. These algorithms might weigh certain genetic markers differently, employ various statistical models, or use different approaches to account for the complexities of human migration and admixture.
"Admixture" Calculations: When your DNA is compared to reference populations, the algorithms essentially calculate how much of your DNA "admixtures" or aligns with each group. The way these calculations are performed – the specific statistical methods used – can lead to different outcomes. For example, one algorithm might be more sensitive to subtle genetic variations that indicate a specific European region, while another might be more conservative in assigning those finer distinctions.
Defining Ethnic Boundaries: What constitutes "Scottish" or "Italian" genetically can be a nuanced question. Algorithms have to make decisions about where to draw these lines. AncestryDNA and MyHeritage might draw them in slightly different places, leading to variations.
Interpreting Shared Ancestry: For regions with historically intertwined populations (like the border regions of Ireland and Scotland, or parts of Central Europe), distinguishing between closely related groups can be challenging. The algorithms might interpret these shared genetic signatures differently.

Think of it like two different chefs using the same ingredients to make a dish. They might use slightly different techniques, adjust seasoning ratios, or prioritize certain flavors, resulting in dishes that are similar but not identical. Similarly, the algorithms, while aiming for accuracy, can arrive at subtly different conclusions.

3. The Building Blocks of Your DNA: Markers and SNPs

Your DNA is comprised of billions of chemical bases, but DNA testing kits don't analyze every single one. Instead, they focus on specific locations within your genome known as Single Nucleotide Polymorphisms (SNPs). These are single-letter variations in your DNA sequence that are common among humans. By analyzing the patterns of these SNPs, companies can infer your ancestry.

The impact of tested markers:

Coverage Differences: AncestryDNA and MyHeritage test different sets of SNPs. While there's considerable overlap, each company has its own proprietary chip that targets specific regions of the genome. This means that the exact genetic information being analyzed can vary.
Marker Selection: The selection of which SNPs to test is crucial. Some SNPs are more informative for distinguishing between certain populations than others. One company might choose SNPs that are highly differentiating for a particular European group, while another might prioritize SNPs that offer broader continental insights.
Data Granularity: A difference in the number and selection of tested SNPs can impact the granularity of the results. If a company tests more SNPs within a specific gene region known to be associated with a particular ancestry, they might be able to make a more precise assignment than a company that tests fewer SNPs in that same region.
Technological Advancements: As technology advances, companies update their testing chips, potentially testing more SNPs or different types of genetic markers. This can lead to changes in your results over time, even if you haven't done anything different.

Therefore, if AncestryDNA tests a set of SNPs that are particularly indicative of, say, Scandinavian ancestry, while MyHeritage tests a different set that doesn't capture that specific genetic signature as strongly, you'll see a difference in your Scandinavian percentages.

4. The Echoes of History: Immigration and Population Genetics

Understanding historical migration patterns is vital to grasping why your DNA results might differ. The genetic makeup of a population is a direct result of centuries of movement, intermingling, and isolation.

How history plays a role:

The Melting Pot of America: The United States, in particular, is a prime example of a “melting pot.” Generations of immigrants from diverse European countries, as well as other parts of the world, have intermarried and settled in various regions. This creates complex genetic profiles where individuals might have a mosaic of ancestries.
Regional Variations within Continents: Even within a continent like Europe, there are distinct genetic clusters that often correlate with historical kingdoms, geographical barriers (like mountain ranges or coastlines), and trade routes.
AncestryDNA's U.S. Focus: AncestryDNA’s reference populations are heavily weighted towards the genetic makeup of people in the United States. This means they are adept at identifying the common blends of European ancestries that have historically settled in America.
MyHeritage's European Nuances: MyHeritage, with its significant European user base and extensive European reference panels, can often pinpoint more specific European regional origins. This is because they have more data on the subtle genetic differences between, for example, different regions of Germany or Scandinavia.
The "Irish" vs. "Scottish" Conundrum: Many individuals with ancestry from Ireland and Scotland share a significant amount of DNA due to historical connections and intermingling. Both companies might assign percentages, but the exact split can vary based on their reference groups and algorithms. If your family has roots in the Ulster Plantation, for instance, you might see interesting variations between the two.

Essentially, the way a region's genetic history has been shaped by migration can make it more or less distinct for different testing companies.

5. Staying Current: Updates to Databases and Algorithms

The field of genetic genealogy is constantly evolving. Both AncestryDNA and MyHeritage regularly update their reference populations and algorithms as they gather more data and refine their scientific understanding.

Why updates matter:

Expanding Reference Populations: As more people test their DNA, companies can add new reference panels, increasing the accuracy and detail of their ethnic estimations, especially for underrepresented groups.
Algorithm Refinements: Scientists are continuously improving the algorithms used to analyze DNA. These updates can lead to shifts in your percentage breakdowns. What might have been categorized as "General European" a few years ago might now be more specifically identified as "English," "German," or "French."
Impact on Previous Results: If you tested your DNA several years ago and have recently re-downloaded your results or re-analyzed them, you might notice changes. This is often due to these updates rather than a change in your actual DNA.
Consistency vs. Evolution: While companies strive for consistency, the pursuit of greater accuracy means that your results from a specific company might change over time as their scientific understanding deepens.

It’s a good practice to periodically check for updates from your testing providers, as these can offer new insights into your ancestral makeup.

6. Deeper Dives: Paternal vs. Maternal DNA and Autosomal DNA

It's important to understand that most consumer DNA tests analyze autosomal DNA. This is the DNA inherited from all your ancestors, both maternally and paternally, across all your chromosomes (except for the sex chromosomes). However, some services also offer specialized tests for Y-DNA (paternal line) and mitochondrial DNA (maternal line).

Autosomal DNA is where most of the differences in ethnic estimations arise:

Autosomal DNA (Most Common): Both AncestryDNA and MyHeritage primarily provide autosomal DNA ethnicity estimates. This DNA makes up about 99% of your genome and is passed down from all your ancestors. The percentages you see for broad ethnic categories are derived from this autosomal DNA.
Y-DNA (Paternal Line): This DNA is passed down from father to son. It can trace your direct paternal lineage back thousands of years.
Mitochondrial DNA (mtDNA) (Maternal Line): This DNA is passed down from mother to child (both sons and daughters). It traces your direct maternal lineage back thousands of years.

Why this distinction is relevant to your question:

Focus on Broad Ancestry: Since autosomal DNA is a blend of all your ancestors, the interpretation of its ethnic makeup is the most complex and thus most prone to variations between companies.
Specialized Tests Offer Different Insights: If you were to compare Y-DNA or mtDNA results from a company that offers them (like FamilyTreeDNA) with your autosomal results from Ancestry or MyHeritage, you'd be comparing apples and oranges. These specialized tests provide much more focused lineage information.

For the ethnic percentages you see on AncestryDNA and MyHeritage, you are almost certainly looking at autosomal DNA results. The differences between them stem from how each company interprets this complex blend of inherited DNA.

7. The Interplay: Genetic Ancestry vs. "Paper Trail" Ancestry

One of the most common points of confusion arises when genetic ancestry results don't perfectly align with what individuals have learned through traditional genealogical research (often referred to as the "paper trail").

Understanding the disconnect:

DNA is a Reflection of Actual Biological Inheritance: Your DNA is a record of your direct biological ancestors. It tells you what genetic material you inherited from whom, regardless of surnames, adopted heritage, or historical records.
Paper Trails are Records of Families, Not Necessarily Biology: Genealogical research relies on historical documents like birth certificates, marriage licenses, census records, and family stories. These records can sometimes be incomplete, inaccurate, or reflect familial relationships that aren't purely biological (e.g., adoption, or names taken from a non-biological father).
The "Missing" Ancestry: Sometimes, you might have a documented ancestor from a certain region (e.g., a great-great-grandfather born in Poland), but your DNA doesn't show a significant Polish percentage. This can happen if that particular ancestor didn't contribute a large or distinct enough genetic signature to your overall autosomal DNA, or if the reference populations aren't detailed enough for that specific region.
Surprising Genetic Discoveries: Conversely, you might have DNA percentages that point to an ancestry you weren't aware of. This can be a fascinating opportunity to explore new branches of your family tree.
Consanguinity and Assimilation: In regions with historical assimilation or where many people from the same broad ethnic group migrated and intermarried (like much of the United States), it can be harder for DNA tests to distinguish between very closely related ancestries (e.g., distinguishing definitively between English and Welsh, or between different sub-regions of Ireland).

Your DNA results provide a picture of your biological heritage, while your paper trail provides a record of your family's documented history. These two can be complementary, but also distinct, providing a richer, more nuanced understanding of your origins.

Making Sense of Your Results: Best Practices for Genealogists

So, how do you navigate these differences and make the most of your DNA testing experience? Here are some practical tips:

1. Embrace the Complementary Nature of the Tests

Instead of viewing the differences as errors, see them as complementary pieces of a larger puzzle. AncestryDNA might highlight a larger broad European percentage, while MyHeritage could break that down into more specific European regions. Use these insights to guide further research.

2. Focus on the Overlap

Look for the ancestries that both AncestryDNA and MyHeritage consistently identify. These are likely to be your most significant genetic contributions. For example, if both tests show you have a substantial percentage of Irish and German ancestry, you can be fairly confident in those findings.

3. Investigate the Differences

If there's a significant difference in a particular ethnic category, try to understand why.

Research the Reference Populations: Look at the specific countries and regions that make up each company's reference panels.
Consult Historical Records: Does the differing result align with any known or suspected ancestral lines in your paper trail?
Consider Immigration History: If you have ancestors who immigrated from areas with mixed populations, this can explain discrepancies.

4. Treat Percentages as Estimates, Not Exact Figures

It's crucial to remember that ethnic percentages are estimations. They are not definitive pronouncements but rather the best interpretation the science can offer based on current data. Small fluctuations are normal and expected.

5. Use DNA Matches Wisely

While ethnicity estimates are interesting, the true power of DNA testing often lies in connecting with relatives through shared DNA matches. Both AncestryDNA and MyHeritage have extensive databases of DNA matches. Comparing your matches across both platforms can reveal new familial connections.

6. Don't Discard One Test for the Other

Each test offers unique value. AncestryDNA’s vast user base in the U.S. can lead to a higher number of potential close matches. MyHeritage’s detailed European breakdowns can offer more regional specificity. Both are valuable resources.

7. Consider Uploading to Other Databases

Many people choose to upload their raw DNA data (usually a .vcf file) from AncestryDNA or MyHeritage to other platforms like GEDmatch, which allows for more in-depth analysis and comparison with a wider range of reference populations and genetic analysis tools. This can sometimes help reconcile differences or uncover new insights.

The Takeaway: A Richer Tapestry of Your Heritage

In conclusion, the differences you observe between your AncestryDNA and MyHeritage results are not signs of flawed testing but rather a testament to the complex and evolving nature of genetic genealogy. By understanding the roles of reference populations, algorithms, tested markers, historical migration, and ongoing scientific updates, you can interpret these variations with greater confidence.

Embrace the journey of discovery. Your DNA is a unique story, and each company offers a different lens through which to read it. By appreciating their methodologies and focusing on both the overlaps and the divergences, you’ll gain a richer, more complete understanding of the incredible tapestry that makes up your heritage.