Population data from Quebec reveals the genetic consequences of rapid human expansions.

The majority of the 6.5 million French Canadians living in Quebec today can trace their heritage to just 8500 settlers who formed clusters around the Saint Lawrence River in the early 17th century. Most remained near those riverside settlements until 200 years later, when some began colonizing more remote regions. Despite their shared heritage, the descendants of those who stayed near the river and those who moved on are already genetically divergent, and for unknown reasons, those living in more recently colonized areas of Quebec have a higher prevalence of recessive genetic disorders.

To understand the relationship between the settlers’ movements and their genetic differences, researchers sequenced the genomes of selected people living near the frontiers and others in the core near the river. They found that, on average, frontier individuals have lower levels of genetic diversity, but their genetic variants are more detrimental than those found in the people in the core are. This pattern is even stronger for mutations that are rare—and, thus, likely more harmful—and the frequency of these rare mutations decreases with their harmfulness in the core population but not in the frontier population.

There are many possible explanations for this—inbreeding, for example—and the researchers needed to take more information into account to determine the true cause. This information came from their own study subjects: the team had specifically chosen the subjects because they could confidently trace the subjects’ ancestry using historical records and detailed genealogical information. Delving into this information revealed that inbreeding was only marginally more common at the frontiers and was nowhere near prevalent enough to account for the genetic differences they observed, allowing them to rule it out as a possible cause.

Combining all three sources of information—historical, genealogical, and genomic data—revealed that the observed harmful genetic variants infiltrated the frontier population via increased genetic drift and relaxed selection. The researchers suggest that this is due to higher fertility and reduced competition at the frontiers, which allowed people living there to transmit their genes irrespective of their intrinsic fitness.

That such a difference between the two groups could manifest in just six to nine generations is remarkable. Although the effect on fitness in most individuals is likely small, the differences could help explain the increased prevalence of recessive genetic disorders in recently settled areas of Quebec. Over a greater number of generations, the effects of relaxed selection would be expected to be more pronounced, so if the same principle applies to the many other waves of human expansions that characterize our genetic history, it may have helped shape how genetic disease burden varies around the world.

CITATION:

Relaxed Selection During a Recent Human Expansion
Stephan Peischl, Isabelle Dupanloup, Adrien Foucal, Michèle Jomphe, Vanessa Bruat, Jean-Christophe Grenier, Alexandre Gouy, K. J. Gilbert, Elias Gbeha, Lars Bosshard, Elodie Hip-Ki, Mawussé Agbessi, Alan Hodgkinson, Hélène Vézina, Philip Awadalla, Laurent Excoffier
Genetics 2018 208: 763–777; https://doi.org/10.1534/genetics.117.300551
http://www.genetics.org/content/208/2/763

 

 

 

, ,

Nicole Haloupek is a freelance science writer and a recent graduate of UC Berkeley's molecular and cell biology PhD program.

View all posts by Nicole Haloupek »

Read more in

  • Thank you, GSA community!

    Thank you for being a member of the Genetics Society of America! As GSA’s current president, I am writing to tell you about Society projects and initiatives that we hope you will find useful in advancing your science and your career. Scientific research is a collaborative and exciting endeavor. Scientific societies like GSA exist to…

  • Collage of 2021 Rosalind Franklin Award recipients

    Where are they now? Rosalind Franklin Young Investigator Award recipients share updates on their research

    Rosalind Franklin Young Investigator Award applications are open–make sure you submit your application or nomination of a colleague by September 30, 2024.

  • University of Minnesota researchers map genome of the last living wild horse species

    The study, published in G3: Genes|Genomes|Genetics, is part of larger conservation efforts to save Przewalski’s horse.

  • Congratulations to the Spring 2024 DeLill Nasser Awardees!

    GSA is pleased to announce the recipients of the DeLill Nasser Award for Professional Development in Genetics for Spring 2024! Given twice a year to graduate students and postdoctoral researchers, DeLill Nasser Awards support attendance at meetings and laboratory courses. The award is named in honor of DeLill Nasser, a long-time GSA supporter and National Science Foundation…

  • Carolyn Damilola headshot

    Carolyn Damilola: an NFS Rising Scientist on a lifelong quest to learn more

    Carolyn Damilola is an NFS Rising Scientist from Nigeria doing respiratory system research and paving the way for scientists from underrepresented communities through mentorship.

  • Text over a blue background image: Apply for up to $2,000 for your project from the Starter Culture Microgrant Program.

    What does a good microgrant proposal look like?

    Members of the Microgrant Review Committee share their tips for a successful proposal.

  • A blurred image of a human face is shown against a dark background.

    The first piece of the facial recognition puzzle

    New research in GENETICS gives a first peek at the molecular pathway involved in recognizing faces.

  • New Senior Editor Amy MacQueen joins GENETICS

    A new senior editor is joining GENETICS in the Genome Integrity and Transmission section. We’re excited to welcome Amy MacQueen to the editorial team.

  • Close up of an adult zebrafish with blue and white stripes in an aquarium with red lighting.

    Block party on the zebrafish sex chromosome

    Research in G3 identifies a gene regulatory block of the zebrafish genome responsible for overseeing the maternal-to-zygotic-transition.

  • Lemna Minor, the common duckweed

    Unraveling the mysteries of duckweed: epigenetic insights from Spirodela polyrhiza

    Research published in G3 offers insight into the impact of DNA methylation on clonal propagation in asexually reproducing plants.

  • Luciano Marraffini headshot

    A microbiologist’s quest to understand CRISPR in bacterial self-defense

    2024 Genetics Society of America Medal recipient Luciano Marraffini determined how CRISPR-Cas systems destroy genetic targets with precision, paving the way for gene editing technology development.

  • Elaine Ostrander headshot

    Unlocking mysteries of trait and disease heritability in dogs

    2024 Edward Novitski Prize recipient Elaine Ostrander, a pioneer of the domestic dog model, discovered numerous genes affecting dog size, morphology, behavior, and disease susceptibility—many of which have relevance in humans.

  • NSF-funded BIO-LEAPS Grant to Support Culture Change in Genetics

    GSA and collaborators Personal Genetics Education & Dialogue and Reclaiming STEM Institute launch NSF-funded BIO-LEAPS project to support culture change in genetics 

    We are thrilled to announce that the Genetics Society of America (GSA) is collaborating with the Personal Genetics Education & Dialogue (PGED) based in the Department of Genetics at Harvard Medical School, and the Reclaiming STEM Institute (RSI) on a Leading Culture Change Through Professional Societies of Biology (BIO-LEAPS) grant from the U.S. National Science…

  • Daman Saluja: Navigating Science and Policy in India

    In the Paths to Science Policy series, we talk to individuals who have a passion for science policy and are active in advocacy through their various roles and careers. The series aims to inform and guide early career scientists interested in science policy. This series is brought to you by the GSA Early Care­er Scientist…

  • Deborah Andrew headshot

    A fly geneticist’s journey into discovering rules of organ development

    2024 George W. Beadle Award recipient Deborah Andrew discovered new genes and pathways in Drosophila salivary gland organogenesis. Now, her work can help optimize cell secretion in therapeutic applications and fight malaria.

  • Małgorzata Gazda's headshot

    Małgorzata Gazda: How receiving the DeLill Nasser Award helped her land her dream job

    Have you ever experienced an event that changes the course of your life, or in this case, your career? Małgorzata (Gosia) Gazda is Assistant Professor at the University of Montreal and in 2022, she received the DeLill Nasser Award for Professional Development in Genetics, which she used to attend and present at the 2022 Population,…

  • Hongyu Zhao joins GENETICS as new Senior Editor

    A new senior editor is joining GENETICS in the Statistical Genetics and Genomics section. We’re excited to welcome Hongyu Zhao to the editorial team.

  • Julio Molina Pineda at TAGC 2024

    GSA Member Julio Molina Pineda Receives DeLill Nasser Award, Shines at TAGC 2024 

    “At any career stage, the GSA membership is an amazing investment for any genetics professional!” Julio Molina Pineda is a PhD Candidate in Cell and Molecular Biology and a Research Assistant at the University of Arkansas, and a Doctoral Academy Fellow at the Lewis Lab. In 2023, Julio was awarded the DeLill Nasser Award for…

  • Ed Grell at his dissecting microscope using ether to anesthetize his flies.

    In Memoriam: Ellsworth Herman Grell (1932–2023), a pioneer of Drosophila genome engineering and annotation

    Ellsworth (Ed) Grell blessed the Drosophila community through three enduring legacies: as a pioneer of chromosome mechanics, as a primary organizer and synthesizer of genetic knowledge in Drosophila, and as a graceful mentor to those fortunate to have known him personally. Ed grew up in rural Nebraska, completed his undergraduate studies at Iowa State, and…

  • Congratulations to the #Fungal24 Poster Award winners!

    We are pleased to announce the recipients of the GSA Poster Awards for posters presented at the 32nd Fungal Genetics Conference! Undergraduate and graduate student members of GSA were eligible for the awards, and a hard-working team of judges made the determinations. Congratulations to all! Felicia Ebot Ojong, The University of Georgia My research is focused…

  • Poster presentation tips for TAGC 2024

    You’ve been selected to present a poster at The Allied Genetics Conference 2024 in March—you’ve celebrated, made plans to attend, now what? This is an exciting opportunity to showcase your research and engage with fellow members of the genetics community, so you want to make sure you’re prepared. We wanted to offer you some tips…

  • Maximize your TAGC 2024 experience 

    A guide to all that National Harbor & DC have to offer Are you joining us for The Allied Genetics Conference 2024 in March? Make the most of your #TAGC24 experience in National Harbor! We know the science will keep you busy, but you deserve to unwind and have some fun, so we’ve curated a…

  • Early Career Leadership Spotlight: Sarah Petrosky

    We’re taking time to get to know the members of the GSA’s Early Career Scientist Committees. Join us to learn more about our early career scientist advocates. Sarah PetroskyMultimedia SubcommitteeUniversity of Pittsburgh Research Interest I am interested in understanding adaptation that has been happening recently in populations by dissecting the ways that genes underlying an adaptation…

  • TAGC 2024 Early Career Award Winners

    GSA is pleased to announce the winners of the early career awards presented at The Allied Genetics Conference 2024. These awards are specific to particular TAGC communities and recognize early career scientists’ outstanding work on their respective research organisms. The awardees will present their talks in keynote sessions at TAGC 2024.  Don’t miss the opportunity…

  • Preeminent geneticists recognized with revamped GSA Awards

    In 2022, GSA’s Board of Directors launched an audit to review the five major awards conferred by the Society. Today, we are thrilled to announce the recipients of the reimagined GSA Awards, including the new Genetics Society of America Early Career Medal. The scientists honored this year are recognized by their peers for their outstanding…

  • Fly Board funds outreach programs to spread the word about Drosophila research

    In 2020, the Fly Board voted to use part of its reserve fund to support efforts to increase trainee participation as well as equity and diversity in the Drosophila community. An awards committee decides how the money will be spent each year, and from 2020–2022, the committee posted a very broad call for applications from…

  • New members of the GSA Board of Directors: 2024–2026

    We are pleased to announce the election of four new leaders to the GSA Board of Directors: 2024 Vice President/2025 President Brenda Andrews Professor, University of Toronto It’s an honor to continue my association with the Society by serving as Vice President of the Board of Directors. I have broad knowledge of the ongoing activities…

  • New members of the GSA Board of Directors: 2025–2027

    We are pleased to announce the election of six new leaders to the GSA Board of Directors: 2025 Vice President/2026 President Cassandra Extavour Timken Professor of Organismic & Evolutionary Biology and of Molecular & Cellular Biology, Harvard University, and Howard Hughes Medical Institute Investigator “Read this,” he said, “it will change your life.” My undergraduate…

  • Congratulations, Spring 2025 Victoria Finnerty Travel Award recipients!

    The Victoria Finnerty Undergraduate Travel Award supports conference-attendance costs for undergraduate GSA members who are presenting research at the Annual Drosophila Research Conference. #Dros25 will be held in San Diego, CA from March 19–23, 2025. Victoria Finnerty, who died in February 2011, was a long-time member of the Genetics Society of America and served the Drosophila community and the genetics community at large in…

  • Meet embGAN, a revolution for cell lineage studies

    New research in GENETICS reports an automated pipeline for cell lineage tracing that massively reduces manual analysis time.