The United States' first African-American president is likely a descendent of the first documented enslaved African in colonial America, researchers at Ancestry.com said today.

"I don't even know the words to describe it," Anastasia Harman, the lead family historian for Provo, Utah-based Ancestry.com, said. "It's amazing. It's seemingly unbelievable, but the research strongly suggests that this is the only possibility."

President Obama is the 11th great-grandson of John Punch, a black man who came to America in the 1600s as an indentured servant and was enslaved for life in 1640 after trying to escape his servitude, according to a two-year Ancestry.com study of thousands of records from colonial Virginia.

Although Obama's father was a black man from Kenya, his ties to slavery stem instead from his white mother, Stanley Ann Dunham, Harman said. The enslaved, black Punch had children with a free white woman. Because their mother was free, Punch's mixed-race kids were born free and went on to become "prominent" land owners in Virginia, Harman said.