Henry Louis Gates Jr. Reveals How Stars Get on Finding Your Roots: 'We Have a Long Waiting List' (Exclusive)

With Finding Your Roots in its tenth season, the PBS show now finds itself in the enviable position of not having to worry about scrambling to book celebrity guests.

“We have a long wait list,” Henry Louis Gates Jr. tells PEOPLE. “We could do Finding Your Roots every week for a year and still not catch up with all the people we have on our waitlist.”

Since its premiere in 2012, the popular docuseries has uncovered the family trees of many celebrities, often with surprising results. Edward Norton learned that he and Julia Roberts are genetic cousins, Kerry Washington discovered she was conceived through a sperm donor, and Viola Davis found out that she’s related to Anita Hill. Just this season, Better Call Saul star Bob Odenkirk realized he’s linked to European royals and is the 11th cousin of King Charles.

Gates now explains the show books guests two ways.

“Sometimes people contact us and ask if they can be in the series, and, often, they’re middle-aged people who have had children,” he says. “Before they have children, they're not particularly interested. But once they have children, they want to know where they come from. They want to know who their ancestors are.”

He continues, “The other way is that we have huge whiteboards in our production offices, and we all just submit candidates. I might be watching the Emmys or the Grammys or the Oscars or go to a movie and say, ‘Hey, I heard this person. I heard they’re recording.’ Or, ‘I saw them in this film. I saw them on Broadway. Why don't we ask them?"

And now, after Gates noticed an uptick in Finding Your Roots fans' desire to see themselves on the program, the chance to retrace one's family history isn't just for celebrities.

"People stop me and they say, 'Look, we love your show, but how about me? How about an average person?'" he shares. "Finally, I implored the producers, and I said, 'We have to speak to this request.'"

Producers took Gates' feedback to heart, allowing viewers to apply. About 9,000 people submitted videos, which were narrowed down to 10. After several months of debate, three people were picked to be featured in an episode that airs later this season.

"We couldn't pick one. We were tied, so we picked three," Gates says, adding, "It turns out that the stories of non-celebrities are just as riveting, just as emotional and just as challenging."

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Finding Your Roots airs Tuesdays at 8 p.m. ET on PBS.