Combining data types refines grasp of French Canadian ancestry in Quebec, revealing how local topographies influenced relatedness, and more
Combining a comprehensive dataset – including marriage documents – compiled from more than 4 million Catholic parish records with genotype data for more than 22,000 French and French Canadian individuals, researchers have conducted a novel analysis of French Canadian ancestry in Quebec, Canada, since the 17th Century. While most other population genetic models provide only coarse representations of a region’s real-world ancestry, this new approach reveals detailed insights into historic European colonization, migration, and settlement patterns, reflecting intricate French Canadian population structures within geographic constraints. What’s more, using the combined datasets, Anderson-Trocmé et al. developed a freely accessible simulated whole-genome sequence dataset with spatiotemporal metadata for more than 1.4 million individuals, enabling future researchers to investigate Quebec’s population genetics at an unprecedented resolution. The migration and dispersal of humans across geographic landscapes can be reconstructed through population genomic analyses. However, for most models, discerning the relationship between spatial migrations and continuous genetic variation within a given population has been difficult and occasionally misleading. Luke Anderson-Trocmé and colleagues leveraged a population-scale spatial pedigree compiled from 4 million historical parish records from across Quebec and genotype data from 2276 French and 20,451 French Canadian individuals to finely model French Canadian ancestry – and how it was shaped by the region’s geographic features. Anderson-Trocmé et al. found that most individuals in Quebec derive ancestry from ~8500 settlers who migrated from France in the 17th and 18th centuries and that the first 2600 French colonizers contributed two-thirds of the French Canadian gene pool. What’s more, the authors show that geographic features, particularly its river networks, considerably shaped Quebec’s population structure, defining major axes of migration and genetic relatedness.
JOURNAL
Science
ARTICLE TITLE
On the genes, genealogies, and geographies of Quebec
ARTICLE PUBLICATION DATE
26-May-2023
Mapping the genetic history of French Canadians through space and time
First study to incorporate genealogical records to provide an accurate map of genetic relatedness
Peer-Reviewed PublicationIMAGE: THE ICE BRIDGE ON THE ST. LAWRENCE RIVER BETWEEN QUÉBEC AND LÉVIS, QUEBEC, CANADA, IN 1892. CREDIT: BIBLIOTHÈQUE ET ARCHIVES NATIONALES DU QUÉBEC view more
CREDIT: BIBLIOTHÈQUE ET ARCHIVES NATIONALES DU QUÉBEC
Though we all share common ancestors ranging from a few generations to hundreds of thousands of years, genealogies that relate all of us are often forgotten over time. A new McGill University-led study is now providing insight into the complex relationship between human migration and genetic variation, using a unique genealogical dataset of over five million records spanning 400 years to unravel the genetic structure of French Canadian populations.
The team, including researchers from Université du Québec à Chicoutimi and the Big Data Institute at the University of Oxford, developed a new method to simulate genomes based on a population scale genealogy dating back to the arrival of the first French settlers. By comparing the simulations to real genetic data, they were able to prove that the genetic structure of this population was encoded within its genealogy.
“It is the first genetic study, in any worldwide population, that incorporates genealogical records to provide a strikingly accurate map of genetic relatedness at the population scale,” explains Simon Gravel, Associate Professor in McGill’s Department Human Genetics and one of the study’s authors.
How rivers and mountains influenced population structure
The dataset was used in part to investigate how certain historical events and landscapes have influenced the genomes of French Canadians today. The study highlights the relationship between river networks and genetic similarity, as European colonial history was marked by a rapid expansion of borders along the banks of the St. Lawrence River and its tributaries.
“This study tells the genetic story of French Canadians, showing that their population structure today is not a result of ancestral French population structure, but rather one that has been shaped by events in North America over the past four centuries,” says Prof. Gravel. “We were even able to tie a meteor impact crater in the region of Charlevoix, to the appearance of a founder effect observed in the Saguenay-Lac-Saint-Jean region.”
Using ancestral data to help identify genetic diseases and treatments
By tracing the ancestry of millions of individuals over space and time, the study bridges the gaps between family pedigrees and continental population structure, providing valuable insights into the complex tapestry of human genetic history. “Beyond mapping the rich genetic history of French Canadians, the findings have significant implications for understanding the impact of migration on genetic variation and the broader history of humanity,” adds Prof. Gravel.
The researchers are hoping that the large, freely available simulated dataset with realistic population structure and mating patterns will help improve genetic risk prediction, historical inference, and genealogical inference, which could have potential implications for identifying genetic diseases and improving medical treatments.
About the study
“On the Genes, Genealogies, and Geographies of Quebec” by Simon Gravel and al. was published in Science. A French version is available here.
JOURNAL
Science
METHOD OF RESEARCH
Computational simulation/modeling
SUBJECT OF RESEARCH
People
ARTICLE TITLE
On the Genes, Genealogies, and Geographies of Quebec
ARTICLE PUBLICATION DATE
25-May-2023
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