Study creates ‘most comprehensive’ map of population bottlenecks across human history

Infographic depicting facts about population bottlenecks found throughout human history
Stella Ranelletti/Staff

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Founder events, or population bottlenecks in which the genetic information of small groups of individuals become a large part of the total population, were found to be common throughout human history, according to a campus study published Thursday.

The authors of the study created and utilized a program called the Allele Sharing Correlation for the Estimation of Non-equilibrium Demography, or ASCEND, to create a map of founder events throughout history, according to lead author Rémi Tournebize. The study was funded by the Burroughs Wellcome Fund, a Sloan Research fellowship and the National Institutes of Health, according to Priya Moorjani, senior author and campus assistant professor of molecular and cell biology.

“Our study provides, to my knowledge, the most comprehensive atlas of the spatiotemporal distribution of founder events in humans,” Tournebize said in an email. “This is thanks to the ever-increasing availability of genetic resources for present-day and ancient samples, as well as the computational tractability of our new method, ASCEND.”

The large amount of genetic samples available and ASCEND the researchers to uncover founder events that had not previously been identified, such as populations in ancient Morocco and Siberia, according to Tournebize.

ASCEND works by measuring DNA shared between individuals within and across populations, according to Tournebize. While the program ran slowly at first, collaboration with campus graduate Gillian Chu allowed the addition of a feature the led to ASCEND to run up to a “hundredfold” quicker, Tournebize added.

“It is a major technical improvement and really required dedicated work for a few weeks because it is a completely different way to frame the problem compared to what I was used to,” Tournebize said in the email. “I personally found it amazing how taking a different perspective from another field on the same problem made such a difference.”

According to Tournebize, because of how founder events could lead to populations having higher frequencies of disease-causing mutations, the study can provide information for future studies about medical genetics. The results of the study also provide insight into the events that caused founder events, according to Moorjani.

The researchers additionally applied ASCEND to dogs to show the versatility of the program and it revealed that nearly all the dog breeds studied had extreme founder events in recent history, according to Tournebize. Tournebize added this contrasted with the widespread history of founder events in human populations.

“Human history is already important in many people’s mind and heart. Asking ‘where we come from’ … has been at the heart of human thoughts for millennia,” Tournebize said in the email. “The cross-talk between historians and genetic-based demographic inference is extremely important and will help to bring a comprehensive understanding of major population movements and impact of cultural changes in our history.”

Contact Tiffany Lieu at [email protected], and follow her on Twitter at @tiffanyplieu.