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Founder Events Common in Human, Dog Populations, Study Finds

NEW YORK – A significant proportion of human and dog populations carry genetic signatures pointing to past founder events — the advent of new populations stemming from bottlenecks that leave only a subset of individuals from the existing population behind.

"Our analysis highlights a widespread history of founder events in humans and dogs and elucidates some of the demographic and cultural practices related to these events," senior and co-corresponding author Priya Moorjani, a researcher at the University of California, Berkeley, and her colleagues wrote in PLOS Genetics on Thursday.

With the help of a computational method called "allele sharing correlation for the estimation of non-equilibrium demography," or ASCEND, the researchers searched for signs of founder events in 460 human populations and dozens of domestic dog breeds, based on genome-wide allele sharing patterns gleaned from array-based genotypes for thousands of individuals profiled for prior projects.

From there, the team went on to look at the strength of the founder events, along with their distribution over space and time. Such events turned up in around half of the human populations profiled, including populations where founder events have been documented in the past.

"We were surprised to see how widespread the history of founder events is in humans, both in present-day and ancient DNA samples," Moorjani and first author Rémi Tournebize, also at UC Berkeley, said in a statement, "suggesting that investigation of disease-causing variants will be fruitful to identify and reduce disease burden among contemporary groups."

Using data for dozens of dog breeds and village dog groups, the team also documented founder events in dogs. These events appeared to be particularly common since the advent of breeding programs going back to the Victorian era.

Founder events lead to genetic diversity declines within populations that can concentrate specific disease-related variants, including those linked to recessive conditions, the team explained. For example, conditions stemming from such variants have been found in Ashkenazi Jewish, French Canadian, Finnish, and Amish populations, leading to genetic screening programs in some cases.

"Some human populations like Ashkenazi Jews or Finns have been extensively studied in population genetics and have helped researchers identify many disease-causing mutations," Moorjani and Tournebize explained. "Hence, we wanted to study if other populations have a similar history that could enable further progress in medical genetics."

In an effort to get a more complete view of founder events across human populations, the researchers initially brought together data for more than 2,300 modern-day individuals from 184 human populations genotyped with the Affymetrix Human Origins array, detecting recent founder events in 113 of the populations.

Such events appeared to be most common in populations from Oceania or the Americas, the team noted, being detected in up to 80 percent of the groups considered. Founder events were documented in a smaller proportion of the European groups analyzed.

Likewise, the timing of the founder events tended to vary by location and over time, according to the researchers — patterns that the team investigated further using ASCEND analyses on still other present-day populations, as well as 160 ancient populations.

"Our results suggest that geographic isolation, modes of sustenance, and cultural practices are notable predictors of founder intensity," they reported, noting that "populations living on islands have experienced stronger founder events than continental groups."