RACHEL SWARNS: It does.

And I was able to find the mystery white ancestors in her family tree, and their descendants. And they, as you might imagine, really grappled with this. It's hard to look back and to know that your family may have owned the first lady's family, in fact, indeed did own the first lady's family, and, worse still, that your ancestor may have raped a member of the first lady's family. These are not easy things to think about.

GWEN IFILL: And there's really no way to tell, in the kind of research you did, what the nature of the relationship was between Melvinia and the man who fathered her child.

RACHEL SWARNS: Right. There's no way to know.

GWEN IFILL: And Dolphus Shields, he's a key character in this. Tell me about him.

RACHEL SWARNS: So he is the first lady's great-great-grandfather. He was biracial, born a slave.

And he really carried the family forward. He became a carpenter. He became a property owner. He became—he ran his own business. He founded churches. When he died, his obituary ran on the front page of the black newspaper in Birmingham at the time.

GWEN IFILL: And we think that he had a relationship, perhaps, with his white father, even if he didn't know it was his father?

RACHEL SWARNS: Well, we don't know. There are intriguing questions about that.

He left Georgia for Birmingham. And around the time he was living in Birmingham, his—he had a white half-brother who also lived in Birmingham. And there are people who knew Dolphus who said that he talked about having a white brother. Whether that really was this half-brother, whether he knew who his father really was, we don't know.

GWEN IFILL: In putting this all together, in knitting this all together, did you talk to current-day members, descendants of this—of this tree?

RACHEL SWARNS: Yes, I talked to members black and white. Some of them actually got together quite recently.

GWEN IFILL: Tell me about that.

RACHEL SWARNS: Yes.

They—the town where Melvinia once lived as a slave decided to erect a monument to Melvinia after the story that appeared in the front page of The New York Times. And they had a ceremony. Some of Melvinia's descendants were there.

And, at the last minute, I thought maybe some of the white descendants would like to come. And they did. Some drove from Birmingham and parts of Alabama. And some came from Georgia.

GWEN IFILL: Wow.

RACHEL SWARNS: It was quite something to see.

GWEN IFILL: I will bet. I will bet it was.

Yet, along the way, there has always been a certain amount of shame and secret-keeping that goes with this kind of connection. And I want you to read a passage from the book that I asked you to take a look at that kind of captures—at least in reading it, it captured it for me.

RACHEL SWARNS: "That reluctance to probe the past, to look back over one's shoulder, to examine the half-healed sores that festered in grandparents and great-grandparents reappears over and over again in Mrs. Obama's family tree.

"It has made the search for the truth that much harder. But it is also understandable.

"People often turn away from what is too painful to witness. They almost always want their children to see the world as a better place, to be free of their pain."

GWEN IFILL: In meeting with the descendants, as they met each other for the first time recently, did it seem as if they had transcended that pain?

RACHEL SWARNS: I think they were willing to grapple with it.

And I—I think, in many ways, they would have wished that this connection might have originated in a different way, but they accepted it and thought that they, as contemporary people, could get to know each other and exchange phone numbers, take a picture, have a dinner.

GWEN IFILL: And do you know if other African-Americans and whites who have grown together and grown apart in our society have also found their way back to each other in this way?

RACHEL SWARNS: Oh, many, many people are doing this all the time.

And when you do these DNA tests, they connect you to your distant cousins. And for many African-Americans, they find they're black, white, and in between.

GWEN IFILL: Fascinating.

Rachel Swarns, author of "American Tapestry," thank you so much.

RACHEL SWARNS: Thank you.