Researchers at Ancestry.com say President Barack Obama is the 11th great-grandson of the first African man to be declared a slave in America, according to CBS News.

The findings were released Monday after researchers spent two years tracing the family tree of Obama’s late mother, Ann Dunham, who was born Stanley Ann Dunham in Kansas in 1942. Dunham’s roots can be traced to a family, the Bunches, descended from a Virginia slave named John Punch. Dunham died in 1995. Obama’s father, Barack Hussein Obama, was born in Kenya.

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In 1640, Punch, who had escaped to Virginia from Maryland, was caught and sentenced to a lifetime of servitude. Researchers say the discrepancy in names is common – record-keepers of the era wrote names down according to how they sounded – but that DNA testing of the Bunch family led them to make the connection.

“We sort of stumbled across it,” lead researcher Anastasia Harman told The New York Times. “We were just doing general research into the president’s family tree, and as we started digging back in time, we realized that the Bunch family were African-American.”

The Bunch family would come to span seven generations across a group of states including Virginia, Tennessee, Arkansas and Kansas.

Obama’s family background has been a point of political contention during his presidency: earlier this year, reality TV show host Donald Trump was one of several Republican figures insisting the president was actually born in Kenya, an allegation a slight majority of Republican voters still seem to buy, even after he released the long-form birth certificate proving he was born in Hawaii.

The findings come just over a month after DNA testing also revealed that the president’s wife, Michelle Obama, is related to members of several white families, including some who fought for the South during the Civil War.

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Watch CBS News’ report on the discovery, aired July 30, below: