Dr. Kasia Bryc is a geneticist who studies how human DNA reflects our shared history, including how people moved and mixed over time. She earned her PhD from Cornell University and has worked in both academic and industry settings, including at 23andMe and the Broad Institute of MIT and Harvard. Her research explores how ancestry from different populations gets passed down through generations and how those patterns show up in modern DNA. Today, Kasia is a Senior Research Scientist at the Broad Institute and serves as Director of Research and Scientific Engagement at Darwin’s Ark, where she helps connect complex genetic research with public participation and accessible science communication.
Your research journey began with a blend of mathematics and computational science before moving into genetics. What first drew you to population genetics and how did your training shape your interests?
I always loved math, statistics, problem solving, and proofs. In high school, I participated in math competitions for fun. And I’ve always been interested in human evolution— how humans came to be who they are, why I had red hair (see my blog post on the genetics of red hair). It wasn’t until my senior year of college that I realized that the field of population genetics existed. I discovered that I could combine my interests in math and statistics to study patterns in DNA and learn about the forces shaping the human genome. Since DNA is passed down from generation to generation, it carries a record of human demographic history. You can query signals in the DNA to ask questions about our human past. That realization drove my graduate work, and I was very fortunate to do my training at such an exciting time, just when genetic data was exploding in size. For the first time, scientists could ask all manner of questions and uncover discoveries that had never been possible before.
You’ve worked across academia and industry, including significant work at 23andMe and now at the Broad Institute. How did those environments influence your scientific approach?
Great question! I’ve really enjoyed working in both environments. There’s nothing like academia for focusing on really interesting questions and letting the discoveries guide your research direction. But my experiences in industry helped me really understand how to break down a research project to drive it forward rapidly, and I also learned a lot of practical management and technical skills that have made me a much more organized and effective scientist today.
Population genetics often deals with big questions about human history and identity. What does this field allow us to see about ourselves that other scientific disciplines do not?
Well, to quote Dr. Henry Louis Gates Jr., the “DNA don’t lie.” What that refers to is, while genetics doesn’t necessarily explain how or why something happened, it does, at a high level, reflect the past, even when those truths are inconvenient. This is the case for individuals who may have been told one story about their ancestors when their actual ancestry is different. A lot of my work on sex bias in ancestry contributions, cryptic African ancestry in white Americans, and even ancestry differences across the U.S. really paints the picture of the genetic impacts of the Trans-Atlantic Slave Trade in a way that can be difficult to unearth from historical documents.
Your work uses DNA to uncover how human populations are connected across time and place. Can you share a finding that surprised you or shifted your perspective?
When I first started studying admixture in African Americans from the U.S., looking at African vs. European ancestry proportions, we knew that there was a lot of variability in ancestry among individuals. Our research showed that, on average in African Americans, about a quarter of the genome is of European ancestry. However, some individuals have entirely African ancestry while others carry less than 50% African ancestry.
What was more surprising was that many individuals in the U.S. that identify as white, or European American, also had low proportions of African ancestry. This wasn’t just a bias in the estimates. For example, individuals whose four grandparents were born in a European country almost never showed any African ancestry. These individuals were much more likely to live in the Southeastern U.S., which corresponds to places with high African American population density. Up to 10% of European Americans from states in the Southeast carried this “cryptic” African ancestry. I call it cryptic because I suspect that many of these individuals are unaware of this ancestry.
Scientific careers are rarely linear. What were some unexpected twists in your career path, and how did they shape where you are today?
I was in the middle of my postdoc at Harvard Medical School when I bumped into my former Stanford mentor, who had become the Director of Research at 23andMe. The company was relatively young at the time, but already had a growing database of customers who had consented to having their data used for research. We got to chatting about how interesting it would be to compare people’s genetic ancestry with how they self-identify. This conversation turned into a visiting postdoc for me to pursue just that. This body of research came together and was published in AJHG (The American Journal of Human Genetics) and marked the beginning of my time at 23andMe working on research and method development around ancestry.
"I’m really excited for Darwin’s Ark’s pioneering research into the cat genetic space. Never before has anyone attempted to scale genetic research this large in this beloved species." - Dr. Kasia Bryc
As someone deeply involved in both method development and scientific engagement, what is one lesson you learned about communicating complex science to broader audiences?
I have been continuously impressed by peoples' capacity to learn and understand complex concepts, and I never wish to underestimate community scientists whose ideas and contributions are incredibly informed and powerful.
Looking back, what is one thing about building a career in genetics or data science you wish you had known sooner?
Right now, I’m really appreciative of all the work that goes into creating these rich genomic datasets. There is so much work that happens “under the hood” to generate large, high-quality datasets. Making sure everything goes 100% correctly doesn’t just happen by accident—it’s a lot of effort to pull all the pieces together. As a computational person, I wasn’t “feet on the ground” to generate these datasets and so I wish I could go back and thank all of my colleagues and collaborators for their roles in collecting and generating the amazing datasets I had the privilege of working with.
What role does diversity—in both people and genetic data—play in making science stronger and more insightful?
Including diversity in genetic research is not just morally the right thing to do, but also scientifically the right thing to do. There are great examples about genetic diversity being crucial for impactful scientific discoveries. But I also think this is true of all forms of diversity, right? Research has shown that diverse teams are more innovative and productive. However, I also think that diversity in research approaches is important. For example, much of what we know about human genetics is actually driven by research across species. By focusing too narrowly, researchers might miss great opportunities to advance our understanding.
What continues to inspire you about your work, and what future questions in population genetics excite you most?
I’m really excited for Darwin’s Ark’s pioneering research into the cat genetic space. Never before has anyone attempted to scale genetic research this large in this beloved species. Millions and millions of cats share our homes, our environments, our exposures. We know our cats so well, so it’s this amazing opportunity to leverage that deep knowledge and relationship. The results could not just help science, and help us better understand our cats, but help improve understanding of genes, pathways, and eventually even improve human health.
