Discovering a close DNA match can send your heart racing—was your family’s story hiding a secret all along? While DNA testing opens incredible windows into our ancestry and relationships, misinterpreting results can quickly steer you off course. Let’s clear up some of the most common pitfalls and ensure your journey into genetic genealogy is both accurate and rewarding.
Misreading the Centimorgan (cM) Numbers
One of the first numbers you’ll see is your shared centimorgans (cM) with a match. But just because a high cM suggests a close relationship, it doesn’t pinpoint the exact one. For example:
- 900 cM could mean a half-sibling, aunt/uncle, niece/nephew, or even a grandparent.
- Lower cM matches often fall within a wide relationship range, too.
Avoid the trap: Always consult relationship charts from top resources (like the Shared cM Project), and consider age, location, and family tree information before drawing conclusions.
Overlooking Endogamy and Pedigree Collapse
Populations that intermarried for generations—such as Ashkenazi Jews, Acadians, and others—display a phenomenon called endogamy. This causes individuals to share more DNA with distant relatives than usual. A high cM count might reflect many shared ancestors, not recent ones.
Avoid the trap: Investigate known population histories and analyze the number of shared segments, not just total cM. Build out your tree as far as possible to spot these patterns.
Ignoring the Power of “Triangulation”
Sometimes, excitement over a new match blinds us to the power of confirmation. Assuming a relationship from one match, without cross-checking with others, can lead to major family tree errors.
Avoid the trap: Look for shared segments between multiple matches—ideally on the same chromosome—to confirm common ancestry (called triangulation). Many platforms supply dedicated tools for this.
Conclusion: DNA testing offers thrilling possibilities, but smart genealogists double-check every clue. By learning the limitations—and leveraging the tools at your disposal—you’ll transform DNA matches from confusion to clarity, and build a family history you can trust.