New research has uncovered surprising findings about President Obama’s ancestry.

Researchers at Ancestry.com have discovered that his lineage does include at least one black slave but not on his Kenyan father’s side. Obama’s white mother is most likely a direct descendant of one of the first documented African slaves in the United States, said the team of genealogists.

Its team, while lacking definitive proof, said its research “strongly suggests” Obama’s family tree — on his mother’s side — stretches back nearly four centuries to a slave in colonial Virginia named John Punch.

In 1640, John Punch, an African, was a servant in Virginia who escaped, was caught and sentenced to remain enslaved to his master for life.

The Ancestry.com team said records suggested that Punch fathered children with a white woman, who passed her free status to those children, giving rise to a family of a slightly different surname, the Bunches. The researchers said over time, as the Bunches continued to marry, they became prominent landowners in colonial Virginia and were known as white.

In the early 1600s interracial marriage was not looked down upon. That view didn’t start until about the 1660s, and it was only in the 1700s that laws came into effect to prohibit racial inter-marriage, said Joseph Shumway, a genealogist at Ancestry.com.

“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 odds, based on what does actually survive, strongly suggest that President Obama is a descendant (he would be the 11th great-grandson) of the first enslaved African in America,” Ms. Harman and her team wrote in a research paper that Ancestry.com released on its website on Monday.

Shumway said the team is extremely confident in the conclusion they have reached. They carried out two years of extensive research examining Obama’s mother’s past, which included DNA analysis and combing through thousands of historical documents.

There is no evidence that Obama’s mother, Stanley Ann Dunham, had any knowledge that she might have had African-American ancestry, Janny Scott, her biographer, told the New York Times:

The Ancestry.com group traced two major Bunch family branches, one that lived as white and stayed in Virginia for generations and another that left for the Carolinas. In North Carolina, the Bunches were recorded as “mulatto” in early records, and their descendants are also the president’s cousins.

Mr. Obama descends from the Virginia branch, which eventually migrated to Tennessee, where his great-great-great-great-grandmother, Anna Bunch, was born. Her daughter, Frances Allred, who was born in 1834, moved to Kansas. Four generations later, in 1942, with the family still in Kansas, Mr. Obama’s mother was born.

When Obama was running for president some argued he was not a “true African-American” because his heritage did not include slavery.

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