'Obama's mother descendant of America's first black slave'

US President Barack Obama's white mother has descended from America's first black slave, a new study has claimed.

A study of the DNA analysis, marriage and property records suggested that Obama is the 11th great-grandchild of John Punch, the first black slave living in colonial Virginia nearly four centuries ago.

While it was known that Obama's mother, Stanley Ann Dunham, had European ancestors, researchers have now discovered that she also had at least this one African American forebear, Ancestry.com reported. The study sheds further light on the American biography of Obama, who last year released his birth certificate to prove he was born in the country and not Kenya, from where his black father hails.

John Punch was captured and condemned to a life of slavery in 1640 for escaping a home where he worked as a servant. The sentence, which came years before Virginia set laws condoning slavery, has led historians to regard him as America's first legally sanctioned slave.

Without the specific date, historians deem Punch to be one of the first certain slaves. Records show Punch fathered children with a white woman, who passed on her free status to them and gave them a slightly different name - Bunch. This name is in Dunham's family tree.

As the Bunches married, they became prominent landowners in Virginia and were known as white, according to the website report. The team traced two Bunch family branches - one that stayed in Virginia and one that moved to the Carolinas. In Virginia, they were known as white, in North Carolina they were recorded as 'mulatto'.

Descendants of this mulatto family - another term for mixed race - are the president's cousins, records show. "In reviewing Ancestry.com's conclusions, I weighed not only the actual findings but also Virginia's laws and social attitudes when John Punch was living," said Elizabeth Shown Mills, a former president of the American Society of Genealogists.

"A careful consideration of the evidence convinces me that the Y-DNA evidence of African origin is indisputable, and the surviving paper trail points solely to John Punch as the logical candidate," said Mills.

"John Punch was more than likely the genesis of legalized slavery in America. But after centuries of suffering, the Civil War, and decades of civil rights efforts, his 11th great-grandson became the leader of the free world and the ultimate realisation of the American Dream," said Ancestry.com genealogist Joseph Shumway.