If you have taken a Y-DNA test and are wondering what to do next, joining a surname project may be one of the highest-value steps available to you. Surname projects are collaborative research groups — hosted primarily at FamilyTreeDNA (FTDNA) — that bring together men who share a surname or its variant spellings, pool their Y-DNA results, and work collectively toward answering questions that no individual tester could resolve alone. For researchers working on Dillman lines, the Dillman DNA Project at FTDNA is exactly this kind of resource: a growing database of Y-DNA results from Dillman men that grows more informative with every participant who joins.
This article explains how surname projects work, what they can tell you, how to read and interpret project results, and why joining — and encouraging male Dillman relatives to test — is one of the most productive investments a Dillman researcher can make.
What a Surname Project Is
A surname project at FamilyTreeDNA is a free, voluntary group administered by unpaid volunteer genealogists with a shared interest in a particular surname. FamilyTreeDNA Group Project administrators are unpaid volunteers who are interested in the genealogy and history of a particular surname, haplogroup, lineage, or geographic region.[1] They have tools to compare results with the rest of the group project and can facilitate communication between members.
The core logic of a surname project rests on a convergence between how surnames and Y-DNA are inherited. In most Western cultures, surnames pass from father to son — and Y-chromosomes (Y-DNA) also pass from father to son, with a predictable rate of mutation. Because surnames are passed down from father to son in many cultures, and Y-chromosomes are passed from father to son with a predictable rate of mutation, people with the same surname can use genealogical DNA testing to determine if they share a common ancestor within recent history.[2] This parallel inheritance means that men with the same surname who share a common paternal ancestor will tend to have very similar Y-DNA profiles — and that similarity can be measured, quantified, and compared.
The practical result is that a surname project can accomplish something no individual Y-DNA test result can do on its own: it can reveal how different Dillman lines relate to each other, identify which participants likely share a common ancestor within a genealogically relevant timeframe (typically the last 500–1,000 years), and group participants into distinct family clusters that correspond to separate Dillman founding lineages.
🧬 How Projects Group Results — and What Groups Tell You
The most informative output of a surname project is its grouping of participants’ results. When enough men have tested, patterns emerge in the Y-DNA data: some participants’ results cluster tightly together, indicating descent from a common ancestor, while others are clearly distinct, indicating separate founding lineages that share only the surname — not necessarily recent common ancestry.
Project administrators typically group results by haplogroup first — the deep ancestral branch of the Y-DNA tree that places a participant’s paternal line within the broader sweep of human prehistory — and then by haplotype within each haplogroup, looking for men whose Short Tandem Repeat (STR) marker values are close enough to suggest a genealogically meaningful relationship. Grouping by subclade is a more refined version of grouping by haplogroup which involves breaking down the haplogroups into more precise groupings. This is particularly desirable when haplogroup groups are large, for example haplogroup R1b.
When a cluster of men shares a surname and similar Y-DNA results, administrators can calculate a modal haplotype for that group — the most common value at each marker position, representing the likely Y-DNA profile of the group’s common ancestor. When a surname project has enough participants’ test results, it can group similar test results together and determine a modal haplotype for each such group of similar test results.[3] The modal haplotype becomes a reference point: new participants can compare their results against it to see whether they likely belong to that family cluster.
For a surname like Dillman — with known origins in German-speaking regions and documented migration to the United States across multiple waves of immigration — the existence of distinct haplogroup clusters within the project is expected and informative. Different haplogroup clusters may correspond to geographically separate Dillman origins in different German states or Swiss cantons, reflecting the historical reality that the Dillman surname arose independently in multiple places rather than from a single founding family.
Reading Y-DNA Project Results
When you view a surname project’s results page at FTDNA, you see a table listing each participant by kit number, earliest known paternal ancestor, predicted or confirmed haplogroup, and their STR marker values. Understanding how to read this table is essential for getting value from the project.
Haplogroup columns. Each participant’s haplogroup is displayed in either green (confirmed by Single Nucleotide Polymorphism (SNP) testing) or red (predicted from STR results). A confirmed haplogroup — obtained through Big Y-700 or targeted SNP testing — places a participant precisely on the Y-DNA tree, often to within a few hundred years of the relevant branching point. A predicted haplogroup is an estimate based on STR patterns and should be treated as provisional, particularly for common haplogroups like R1b where prediction accuracy varies.
STR marker columns. The marker values themselves — DYS393, DYS390, DYS19, and dozens more depending on the test level — are the raw data of the project. Men whose values match or differ by only one or two steps at these markers are likely related within genealogical time. Men whose values differ substantially are either more distantly related or belong to entirely different Dillman founding lineages.
Genetic distance. FTDNA calculates the genetic distance between any two project members — the total number of mutational steps separating their STR profiles. A genetic distance of zero at 37 markers indicates a very close probable relationship (typically within five to seven generations). A genetic distance of four or more at 37 markers makes a recent common ancestor much less likely. The TiP (Time Predictor) tool at FTDNA translates genetic distance into a probability estimate for the number of generations to the most recent common ancestor (MRCA).
Groupings. Administrators organize participants into named groups — typically labeled by haplogroup (R1b Group A, I2 Group B, and so on) or by a geographic or ancestral designation when the lineage is well-established. Ungrouped participants either have not yet been assigned to a cluster or represent outlier results awaiting additional data. Being ungrouped does not mean a participant’s results are uninformative — it may simply mean they are the first representative of a Dillman line that will eventually form its own cluster as more relatives test.
What Surname Projects Can — and Cannot — Tell You
Surname projects are powerful tools for specific research questions and less useful for others. Understanding the boundaries of what project results can tell you prevents misinterpretation.
Projects can confirm or refute a proposed connection between two Dillman lines. If two researchers believe their Dillman ancestors may be related — perhaps descending from brothers who settled in different counties — Y-DNA project results can test that hypothesis. If both men’s results fall in the same haplogroup cluster with a low genetic distance, the hypothesis is strongly supported. If they fall in different clusters entirely, the hypothesis is contradicted.
Projects can identify the geographic origin of a Dillman paternal line. When a Dillman participant’s haplogroup cluster matches closely with other participants whose earliest documented ancestors come from a specific German state or region, that convergence is evidence — not proof, but evidence — of a shared geographic origin. Combined with documentary research, this kind of convergence can suggest which German archive might hold relevant records.
Projects cannot resolve relationships within the last two to three generations from Y-DNA alone. Y-DNA mutates slowly. At 37 markers, two men who are second cousins and two men who are sixth cousins may have identical results — the test cannot distinguish between them. For close relationships, autosomal DNA testing is more informative.
Projects cannot prove a specific genealogical relationship without documentary corroboration. A Y-DNA match tells you that two men share a common paternal ancestor — it does not tell you who that ancestor was, when he lived, or how many generations separate the testers from him. Documentary genealogical research is always required to identify the specific common ancestor that DNA evidence implies.
Non-paternity events complicate project results. Occasionally a participant’s Y-DNA results do not match the expected surname cluster despite a documented family tree connecting them to that surname. This can indicate a non-paternity event somewhere in the patrilineal line — an adoption, an extramarital birth registered under the mother’s husband’s name, or a name change — at any point between the participant and the surname’s origin. These findings can be genealogically significant discoveries in their own right.
Variant Spellings and the Dillman Project
One of the most valuable features of surname projects for Dillman researchers is the systematic inclusion of variant spellings. Surname projects focus on a particular surname and variant spellings of that surname.[5] The Dillman name appears in historical records under numerous spellings — Dillmann, Dillman, Dülmann, Tilman, Tillman, Dilman, and others — reflecting both German orthographic variation and the inconsistent transliteration of German names by American record keepers.
The Dillman DNA Project at FTDNA includes participants testing under variant spellings as well as the standard Dillman form. This is essential: a man whose patrilineal line has consistently used the spelling “Tillman” in American records may in fact descend from the same German Dillmann family as a participant whose line preserved the original spelling. Y-DNA results can reveal that connection where documentary evidence alone might not.
The Role of Big Y-700 in Surname Research
While the standard Y-37 and Y-111 STR tests provide the core data for surname project groupings, the Big Y-700 test adds a layer of precision that is increasingly valuable for advanced surname research. Big Y-700 tests approximately 700 STR markers and scans the entire Y chromosome for novel SNPs — mutations unique to a particular lineage — that can place a participant on a specific branch of the Y-DNA tree that may be shared by only a handful of known men worldwide.
For Dillman researchers, the Big Y-700 has the potential to resolve questions that STR testing cannot. Two Dillman men who appear to be in the same STR cluster may, on Big Y-700 testing, be found to share a terminal SNP that places their common ancestor within a narrow geographic and temporal window — potentially identifying the specific German village or region of origin. Alternatively, they may be found to have diverged at a SNP that predates the adoption of the Dillman surname, confirming that their lines share a haplogroup but not a Dillman founding ancestor.
The results of Big Y-700 testing feed into haplogroup projects — collaborative research groups focused on specific Y-DNA branches — which in turn contribute to an ever-more-refined Y-DNA tree. There is a symbiotic relationship between surname projects and haplogroup projects that is not understood by everyone. The surname projects help people with their genealogies and provide data for the haplogroup projects, while the haplogroup projects do real science which eventually feeds back deep ancestry to the surname projects.
How to Join and Contribute to the Dillman DNA Project
The Dillman DNA Project at FTDNA is administered by the Dillman Family Association (DFA) and is open to all male-line Dillman descendants. The Dillman Family Association is working to find DNA cousins and to establish our Dillman ancestry.[4] This project is open to all male descended Dillmans because of the Y chromosome which is passed from father to son is tested. If you are a Dillman woman, tell your male Dillman relatives of the project; you can join with your research and his sample.
To participate, a male Dillman descendant needs to purchase a Y-DNA test at FTDNA — the Y-37 test is the recommended entry point, providing enough markers to make meaningful comparisons within the project while leaving room to upgrade to Y-111 or Big Y-700 as research questions develop. Women who are researching Dillman lines can contribute by recruiting a male Dillman relative to test and associating that kit with their own research.
To join, contact the project administrator at dnaprojectadmin@dillmanfamilyassociation.org — include “DNA PROJECT” in the subject line. The project is also listed at the FTDNA Dillman project page, where current members can view the activity feed and connect with other participants.
The value of the project grows directly with the number of participants. Every new Dillman tester — whether their line traces to Indiana, Pennsylvania, Ohio, or a German-speaking region — adds data that potentially resolves open questions for every other participant. If you have male Dillman relatives who have not yet tested, encouraging them to do so is one of the most concrete contributions you can make to collective Dillman research.
The Dillman DNA Project is hosted at FamilyTreeDNA (familytreedna.com/groups/dillman/about). Membership is free; Y-DNA testing costs vary by panel size. The project is open to all male-line Dillman descendants and to researchers of variant spellings. Contact the project administrator at dnaprojectadmin@dillmanfamilyassociation.org to join. FamilyTreeDNA Group Projects are administered by unpaid volunteers; project membership can be joined or left at any time.
Sources
- FamilyTreeDNA, “Group Projects,” familytreedna.com/group-project (accessed May 2026).
- Wikipedia, “Surname DNA project,” en.wikipedia.org/wiki/Surname_DNA_project (accessed May 2026).
- ISOGG Wiki, “Matching and grouping in surname DNA projects,” isogg.org/wiki/Matching_and_grouping_in_surname_DNA_projects (accessed May 2026).
- FamilyTreeDNA, “Dillman DNA Project,” familytreedna.com/groups/dillman/about (accessed May 2026).
- FamilyTreeDNA, “Introduction to Group Project Administration,” help.familytreedna.com (accessed May 2026).
AI Disclosure: This article was researched and written with the assistance of Claude, an AI assistant developed by Anthropic. All facts have been reviewed for accuracy, but readers are encouraged to verify information independently, particularly for time-sensitive details such as project membership counts and platform features.
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