The "purity of lineages" as tested by records: what a genealogist can prove, and what he cannot
- Patrice Bourque
- Jun 10
- 7 min read
By Patrice Bourque, Certified Genealogist of Lineage (GFA)
Increasingly, theories based on genealogical premises are being heard in public debate. The so-called "remigration" movement, theorized notably in the writings of Renaud Camus on the "Great Replacement" and, more recently, in those of the identitarian activist Martin Sellner, posits the existence of "pure" lineages, peoples "rooted" since time immemorial in a particular land, and that everyone can be traced back to a single, identifiable ancestral origin. In Germany, the word was even designated "Non-word of the year 2023" by the Unwort des Jahres linguistic jury.
I will not discuss politics here. That is neither my role nor the purpose of this site.
But when a theory is based on genealogical claims, it enters my professional domain, and it becomes verifiable.
Lineage genealogy is a discipline of proof: documents, registers, concordances, documentary standards. So let's ask the question from a technical standpoint: what do the registers say about the "purity of lineages"?
The short answer: it doesn't exist as an object of proof. Here's why.
1. The arithmetic of ancestry is unforgiving
Each of us has 2 parents, 4 grandparents, and 8 great-grandparents. The table doubles with each generation. But what does a "generation" represent in actual years?
In historical demography, a generation corresponds to the average interval between the birth of parents and that of their children: approximately 25 to 30 years, a remarkably stable figure throughout the centuries. This is an important point, because the objection quickly arises: the low life expectancy of the past does not change this calculation. This life expectancy was drastically reduced by infant mortality; those who reached adulthood often lived to 60 or 70, and above all, they became parents between 20 and 30, just as today, sometimes even earlier. The generational interval itself has hardly changed.
Let's translate generations into concrete benchmarks:
10 generations ≈ 250 to 300 years. We are in New France, before the Conquest of 1759. Your ancestry chart already has 1024 positions .
20 generations ≈ 500 to 600 years. Here we are before Jacques Cartier, even before Columbus's first voyage; it's the time of Joan of Arc. More than a million theoretical ancestors.
30 generations ≈ 750 to 900 years. We are in the heart of the Middle Ages: the Crusades, the construction of Notre-Dame de Paris beginning. Your chart requires more than a billion theoretical ancestors... for a world population that then numbered around 400 million.
One billion boxes to fill, 400 million humans available: the math doesn't add up, not by a long shot.
This impossibility has a name in genealogy: pedigree collapse . Our ancestors repeat themselves in our family trees because cousins, close or distant, intermarried. A direct consequence of this is that the further back we go, the more the ancestries of all inhabitants of the same region converge. The work of statistician Joseph Chang, extended by the models of Rohde, Olson, and Chang published in Nature , arrives at a staggering conclusion: the most recent common ancestor of all living humans dates back only a few millennia, and that of European populations, a few centuries. The "pure line," isolated and parallel to others since time immemorial, is an arithmetic impossibility even before it becomes a matter of opinion.
2. Quebec records tell the opposite of purity
Quebec possesses one of the most complete corpora of parish registers in the world, systematically analyzed by the Programme de recherche en démographie historique (PRDH) at the University of Montreal. It is an ideal laboratory. And what does it show?
Franco-Indigenous unions have been documented since the 17th century. Historical works on French America (Havard and Vidal, in particular) and demographic reconstructions show that several perfectly classic "French-Canadian" lineages include an Indigenous ancestor whose descendants today number in the tens, or even hundreds, of thousands of people.
German soldiers who became Quebecers. After the American Revolutionary War, more than a thousand German mercenaries (Brunswickers, Hessians) settled in the province, as documented by Jean-Pierre Wilhelmy. Their surnames were often Gallicized over time in the records, and their lineages blended into the population.
Irish orphans with their surnames intact. During the typhus epidemic of 1847, Quebec families adopted Irish orphans who had passed through Grosse-Île, often keeping their names, as historian Marianna O'Gallagher has established. For seven generations, Johnsons, Ryans, and O'Neils have been at the heart of Francophone families.
Acadians, Scots, English, Loyalists whose descendants indiscriminately populate the two linguistic communities.
And the phenomenon never stopped; it simply changed its faces. The Jewish presence in Quebec has been documented in the archives for over 250 years: the Hart family settled in Trois-Rivières as early as the 1760s, and Ezekiel Hart was elected Member of Parliament in 1807, well before the arrival of the large waves of Ashkenazi Jews at the turn of the 20th century, and then the French-speaking Sephardim from Morocco in the 1950s and 1960s. Italians arrived en masse at the beginning of the 20th century and then again after 1945: parish registers, such as those of Notre-Dame-de-la-Défense in Little Italy, have for generations chronicled Italian-Quebec marriages that have become so commonplace as to be almost unnoticed. Haitians, arriving in two waves starting in the 1960s, helped keep Quebec's schools and hospitals running during the Quiet Revolution; Their grandchildren today have grandparents from Port-au-Prince and Rimouski on the same family tree. The Vietnamese who arrived during the sea refugee crisis in the late 1970s, the Lebanese, the Greeks, the Portuguese, the Chileans of 1973: all now appear in the Quebec civil registry, which is simply the parish register of tomorrow. The genealogist of 2150 who documents the lineage of a Tremblay "from our own backyard" will find a Haitian grandmother or a Vietnamese great-grandfather, just as I find Irish orphans and German soldiers there today.
When a client asks me to document their lineage, I never find a straight line leading back to a single origin. I find a network : migrations, remarriages, children born out of wedlock and recognized later in life, name changes, transatlantic crossings. That's what real ancestry is. The static "rootedness" assumed by these theories doesn't correspond to any case I've opened in my career.
3. Interbreeding is not a boundary between "pure" and "impure"
A clarification is necessary here, because the trap is subtle. Recognizing that mixed ancestry is universal does not mean dividing the world into two camps, the "pure" on one side and the "mixed" on the other. It's precisely the opposite: if all ancestry becomes composite within a documentable timeframe, then the very category of "purity" is emptied. There is no one on the other side of the border. Those who believe themselves to be of immemorial lineage are simply people who haven't yet opened their records.
The nuance also applies in the other direction, and it is just as important: mixed heritage does not erase belonging. Having a mixed ancestry does not diminish the legitimacy of a cultural, linguistic, or national identity. Conversely, ancestry alone is not enough to establish belonging: Indigenous communities, for example, constantly remind us that identity is not limited to a genealogical fraction; it also stems from law, community recognition, and lived culture. This is a principle I see at work concretely in Indigenous lineage mandates: genealogy establishes documented links, but it distributes neither certificates of purity nor patents of exclusion. Anyone who uses the family tree to sort "true" and "false" members of a people makes it say what it cannot say, in either direction.
4. What genealogical evidence can establish, and its limitations
My job is to establish parentage according to strict evidentiary standards: each parent-child relationship must be supported by evaluated, corroborated, and prioritized documents. It's demanding, and that's precisely why I can state this:
Genealogy can prove lineage. It cannot prove "pure" ethnic affiliation.
Beyond a few generations, any ancestry becomes composite. Autosomal DNA tests confirm this by another route: as the scientific literature on genetic ancestry inference has shown (Royal et al., American Journal of Human Genetics ), estimates of "ethnicity" are regional statistical probabilities, recalculated with each update of the reference databases. They are not certificates of purity. Anyone who sells you the idea of an ethnically homogeneous lineage over ten, fifteen, or twenty generations is selling you something that neither records nor genetics can provide.
And this is where the issue becomes serious. Every time in history that a state has tried to classify its citizens by the "purity" of ancestry, from the Nuremberg Laws of 1935 to the Population Registration Act of apartheid South Africa in 1950, it has had to invent arbitrary categories, blood groups, and ethnic registers because documentary evidence refused to cooperate. Genealogists are familiar with these archives as well. They don't bear witness to a science; they bear witness to what happens when genealogy is forced to say what it cannot say.
5. What genealogy really teaches
Paradoxically, my discipline is the best response to these theories. Not by contradicting them with slogans, but by doing its work. Every rigorously documented family history tells the same story: we are all descended from migrants, from unlikely marriages, from crossed borders. Records don't recognize purity; they recognize documented continuity , which is infinitely more interesting.
This is, in fact, the heart of my profession: not to tell people what they are , but to establish, with supporting evidence, where they come from , in all the complexity that this implies.
References
CAMUS, Renaud. The Great Replacement , Paris, David Reinharc, 2011. [Primary source of the movement, cited critically.]
CHANG, Joseph T. “Recent Common Ancestors of All Present-Day Individuals,” Advances in Applied Probability , vol. 31, no. 4, 1999, p. 1002-1026.
CHARBONNEAU, Hubert, Bertrand DESJARDINS et al. Birth of a population: the French established in Canada in the 17th century , Montreal/Paris, Presses de l'Université de Montréal / INED-PUF, 1987.
HAVARD, Gilles and Cécile VIDAL. History of French America , Paris, Flammarion, 2003.
O'GALLAGHER, Marianna. Grosse Île: Gateway to Canada, 1832-1937 , Quebec, Carraig Books, 1987.
Historical Demography Research Program (PRDH), University of Montreal. Database of the Population Register of Old Quebec.
ROHDE, Douglas LT, Steve OLSON and Joseph T. CHANG. “Modeling the recent common ancestry of all living humans”, Nature , vol. 431, 2004, p. 562-566.
ROYAL, Charmaine D. et al. “Inferring Genetic Ancestry: Opportunities, Challenges, and Implications,” The American Journal of Human Genetics , vol. 86, no. 5, 2010, p. 661-673.
SELLNER, Martin. Remigration: Ein Vorschlag , Schnellroda, Antaios, 2024. [Primary source of the movement, cited critically.]
“Unwort des Jahres 2023: “Remigration””, jury press release, Technische Universität Darmstadt, January 2024.
WILHELMY, Jean-Pierre. German mercenaries in Quebec, 1776-1783 , Quebec, Septentrion, 2009.
Note: References to Camus and Sellner are provided to document the premises examined, not to endorse their content.
Patrice Bourque is a Certified Genealogist of Lineage (GFA). He carries out legally valid lineage mandates for lawyers, notaries and institutions, according to the LINEAPROOF™ methodology.
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