President Obama’s extraordinary family story gained a new layer this week as a team of genealogists found evidence that he is most likely a descendant of one of the first documented African slaves in this country.

The link to slavery, which scholars of genealogy and race in the United States called remarkable, was found to have existed approximately 400 years back in the lineage of Obama’s mother, Stanley Ann Dunham. It was discovered by a team of four genealogists from whose findings from two years of work were released in a report Monday.

Using property and tax records, the team uncovered “a lot of context and circumstantial evidence” that points to an enslaved black man named John Punch being Obama’s ancestor, said Joseph Shumway, one of the genealogists who worked on the report.

Because his father immigrated from Kenya and his mother, who was born in Kansas, was white, Obama was thought to have no direct ancestral links to slaves.

“His tree is one of the most dynamic that we’ve seen as far as diversity,” said Shumway, whose company also helped uncover that the president has Irish ancestry and is a distant cousin of Warren Buffett. “There are so many ways that we’ve been able to find interesting stories and connection points.”

The link between Obama and Punch was first reported by the New York Times from an early copy of Ancestry’s report. Punch is a significant historical figure who has long been a subject of research. In 1640, he and two European American indentured servants were arrested for running away from their masters in Colonial Virginia. The two white men received four additional years of servitude, but the black man, Punch, was to “serve his said master . . . for the time of his natural life,” said Peter H. Wood, a professor emeritus of history at Duke University who has written about Africans in Colonial America.

Punch is thought of as the first black slave in Virginia. His was the first documented case of slavery for life in the colonies, decades before institutional slavery was enacted in the state.

“We often need specific names to help us understand sweeping social changes,” Wood said of Punch’s significance. “Punch gives us the story of a real person who endured the beginnings of a huge social shift.”

Interest in the family trees of Obama and his wife has served to upend assumptions, said Sheryll Cashin, a Georgetown University law professor who documented her research into her own family history in the book “The Agitator’s Daughter.”

“It’s absolutely poetic,” Cashin said of the discovery. “Race mixing was here from the beginning.”

The discovery comes at a time when Americans of all backgrounds have been digging deeper into their family trees. It was such familial research that led the team at Ancestry to make the connection between Punch and Obama’s family line.

They first traced Obama’s mother’s heritage through her maternal grandmother to the Bunch family, who at one time lived in Virginia, where they “passed for white” and “intermarried with local white families,” according to the report. Members of the modern Bunch family, who had already begun to dig into their heritage, conducted DNA testing that found that the family had an ancestor from Africa, and they posted that information on a family Web site. Shumway and his colleagues set out to find that black ancestor.

The records eventually led them to Punch, who was one of only 150 Africans living in Virginia in the 1640s and who fathered a free child by a white woman. That the family name changed from Punch to Bunch was not uncommon in an era when there was no standardized spelling, Shumway said.

The revelation about a possible connection “through his ‘white’ ancestors to one of the first Africans enslaved in the colonies is fascinating,” said David Maraniss, an associate editor at The Washington Post and an Obama biographer.

“Most of us are related when you go back far enough, of course, but this family story has a deeper symbolism,” Maraniss said in an e-mail. “Obama has said that his existence has meaning only if it represents the commonality of the human experience, and this genealogical link only reinforces that notion.”

Recent research into Michelle Obama’s ancestry uncovered similar surprises, said New York Times reporter Rachel L. Swarns, who recently published “American Tapestry,” a book on Michelle Obama’s family tree. “She has Irish American ancestors who fought for the Confederacy. Mixed-race ancestors who lived free. African American ancestors who worked on rice plantations,” Swarns said. “It’s the first African American first family. There’s enormous interest in who they are.”

The White House has had no comment on the discoveries, but reflecting on her family tree in 2008, Michelle Obama told The Washington Post that she sees in her family’s history that an “important message in this journey is that we’re all linked. ... Somewhere there was a slave owner — or a white family in my great-grandfather’s time that gave him a place, a home, that helped him build a life — that again led to me.”