A.J. Jacobs, a journalist and bestselling author, thinks he can build a family tree for all of humanity. Here's what he told me about his project, his grandparents, and his most famous ancestor.

You probably know a lot about your grandparents.

But what about your great-grandparents? Your great-great grandparents? And the dozens of generations that came before them?

Journalist A.J. Jacobs, author of The Year of Living Biblically and other bestselling books, is using cutting-edge technology to trace his roots back hundreds of years.

And the more ancestors he discovers, the more ties he can map to the billions of people alive today. Everyone on earth, he says, is his cousin.

A.J. Jacobs is building a family tree for all of humanity.

A.J., 47, who lives in Manhattan with his wife and kids, hopes the family tree he’s building will eventually include all of humanity. In the meantime, he’s staging what could turn out to be the biggest family reunion in history.

The bash, scheduled for June 6 at the New York Hall of Science, will include a scavenger hunt, a talent show, and some barbecue. Scholar Henry Louis Gates will take the stage to discuss his PBS show Finding Your Roots, and the soul group Sister Sledge will perform the song that made them famous, “We Are Family.”

Who’s invited? The whole wide world.

I interviewed A.J. recently about his project, his family, and some of the ancestors he’s identified, including an eighteenth-century Lithuanian rabbi who was regarded by his followers as a saint.

You grew up in Manhattan in the 1970s and 80s. Were your grandparents around much?

A huge amount. I saw them probably twice a month. They all lived here in New York—my maternal grandparents, Ted and Ann Kheel, lived in Riverdale in the Bronx, and my paternal grandparents, Charles and Harriet Jacobs, were on the Upper West Side.

I knew them all quite well.

My mom’s mother loved hanging around with younger people. She said old people talked too much about their aches and pains, so she’d come out to dinner with my friends and me.

A.J., who calls himself a “human guinea pig,” spent a year trying to follow every rule in the Bible and published a bestselling book about the experiment in 2007.

I once said she could be an honorary member of Generation X, and she loved that and brought it up all the time. She’d ask my friends and me, “So, how is the new crop of girls?”

Which is a crazy way to phrase it, but still makes me smile.

Was one of your grandparents particularly special to you?

My mom’s dad, Ted Kheel, was a fascinating man. He was a lawyer and labor mediator who worked on some big strikes in the 60s and 70s.

He used to tell wild stories about his travels to Kenya, about LBJ, and about the artist Christo, who was one of his clients.

How did your grandparents influence you?

My dad’s dad was one of the kindest people I knew, so I try to honor his memory.

My mom’s dad, the labor mediator, was a bold, adventurous type. Even into his 80s, he’d go swimming in the Atlantic Ocean—all the way till November.

Now, I hate cold water, so I won’t be doing that.

But I do admire his boldness and try to emulate it.

A.J.'s grandfather, Ted Kheel, holding his son, Jasper, on a vacation to the Dominican Republic in 2004. Kheel died in 2010, at age 96.
Great-grandfather with baby: A.J.’s grandpa, Ted Kheel, holding A.J.’s first child, Jasper, on a family vacation in the Dominican Republic in 2004. Kheel died in 2010, at age 96. Jacobs family photo.

He also never retired. He kept working in his 90s. I think I inherited some of his workaholism.

You and your wife have three sons. How many grandparents do they have, and do they know them well?

They have three left, and they all live in the New York area. We consider ourselves exceedingly lucky.

At one point, I was considering moving to L.A. for work, but there’s no way we’d leave the grandparents.

How have the boys’ relationships with their grandparents evolved over the years?

I have a son who is 11 and twin boys who are 8. It’s been lovely to see it evolve.

My favorite is part is when they actually have conversations with my parents. They actually listen and (sometimes) respond with (sometimes) relevant thoughts. It’s adorable.

How do your kids’ relationships with their grandparents differ from the relationships you had with your grandparents as a child?

It’s a little less formal.

Just to give you an idea: I called my grandparents “Grandma Kheel” and “Grandpa Kheel”; my kids call their grandparents “Grandma Barbara” and “Grandpa Larry.”

Do you and your wife depend on the kids’ grandparents for childcare or anything else?

Yes, they are a huge help. My mom has weekly dates with our sons. I’ve heard rumors that these dates involve a serious amount of sucrose and fructose, but I’ve been told to mind my own business.

My dad drops off our sons at school once a week.

My wife’s mom plays bridge with them. And my wife’s dad’s second wife—whom we call Granny—has gotten them into mah jong, which I think is hilarious.

They have yet to embrace water aerobics, but give them time.

I know your wife lost both her father and her stepfather recently. Was this hard on the kids? How have they coped?

It was hard. I remember right after Julie’s dad died, we went down to visit her brother for a holiday.

I said to my son, “Aren’t you excited? You’ll get to play on the trampoline.”

And he said, “Yeah, but no Grandpa.”

I found that heartbreaking.

Did you get to meet any of your great-grandparents? What have you learned about them from your research?

I did, but I don’t remember them. They died when I was young.

I loved reading about my maternal grandmother’s mother. She was a suffragist (not “suffragette,” I learned, which is a diminutive). She marched with Susan B. Anthony.

What do you know about your great-great grandparents?

I love the story of my paternal great-great grandfather, who came over from Poland and worked to make enough money to bring over the rest of his family.

He was supposed to pick them up at Ellis Island. But, according to family lore, he missed his train because he was having a second bowl of soup. In his defense, the first one spilled, and his sister insisted he stay and have the second.

What traits do you have in common with your great-grandparents and great-great grandparents?

Well, I’m certainly not as courageous as the ones who came over from Poland. Thank God for them.

You’ve been using new, cutting-edge websites to build your family tree and merge it with trees that other users have created. What are some sites you’ve depended on?

I’ve worked with Geni, WikiTree, MyHeritage, Mocavo, Findmypast, FamilySearch, 23andMe, and Family Tree DNA.

How many generations of ancestors have you traced a connection to? And how many living cousins?

These new family trees on the Internet are remarkable. They’re huge. They’re not even trees; they’re forests of interlocking trees. My direct tree goes back to the 17th century because the rabbis kept good records.

And in terms of width, my tree never ends. If you count cousins by marriage, I have literally millions. My first cousin once removed married actor James Spader, and he’s a super-WASP, so it was nice to hook into the Mayflower crowd through him.

Have you found any distant ancestors whom you think you’d have liked?

I do have an ancestor who was a famous rabbi named the Vilna Gaon. I think I would have both liked him and disliked him. He was apparently a towering intellect, and studied all the time, so I would have loved to hear his wisdom.

But he also didn’t have the best work/life balance. Apparently not the most attentive father. Too busy studying. So I don’t imagine we’d be playing Frisbee together.

Do you have any close cousins you wish weren’t so close?

Well, I do have a first cousin who is quite the character.

Let me give you a little insight into his personality: When he married his wife, he did this shtick where peeked under her wedding dress and pulled off her garter. Then he went under her dress again and pulled out other objects—a Frisbee, a toilet plunger.

And then, he went under and pulled out a little person dressed like a leprachaun who then proceeded to do dirty dancing with him. His friends thought this was hilarious.

I just stared in shock, like the audience in Springtime For Hitler.

But I still love him. I have to. He’s my cousin.