“For 100 years, he didn’t just show us the world… he taught us how to care for it” — happy 100th birthday to David Attenborough, the voice that brought generations closer to nature, history, and the fragile beauty of our planet 🌍✨

Sir David Attenborough is almost a centenarian.

The beloved broadcaster and natural historian turns 100 on May 8. To mark this impressive feat, Attenborough is revisiting the past with a new documentary: Life on Earth: Attenborough’s Greatest Adventure.

The film premieres on Wednesday, May 6, at 8 p.m. ET on PBS and looks back at Attenborough’s groundbreaking series, Life on Earth, which set a new standard for wildlife filmmaking and established the broadcaster as a go-to source for up-close, informative, and respectful animal encounters. A standout moment from the 50-year-old series is its first documentary, which shows Attenborough in Rwanda interacting with gorillas in the wild.

Life on Earth: Attenborough’s Greatest Adventure offers animal lovers and Attenborough fans a behind-the-scenes look at how the landmark series and its magical gorilla moments came to be, including commentary from Attenborough himself.

PEOPLE has a sneak peek at the new documentary, which reveals some of the secrets that have made Attenborough the esteemed natural historian and TV figure he’s been for decades.

In PEOPLE’s exclusive clip, Attenborough shares how he mingled with Rwanda’s gorillas without upsetting the primates.

“You don’t stare at a gorilla. That’s a challenging thing to do, so you keep your head down, and you make these belch vocalizations all the time. And that’s a sort of conversational acknowledgment that you’re in their presence,” he shares in the video as footage of him 50 years ago on Life on Earth plays.

Attenborough’s ability to be present with the gorillas and get close to the wild animals was a surprise to Life on Earth producer John Sparks, who says in the clip that he “only had the expectation of filming David with mountain gorillas in the background.”

“Next thing we know, two youngsters come out and actually sit on him. There was a moment when you barely only saw the top of David’s head, literally, and my jaw dropped, I mean everyone’s jaw dropped, you didn’t expect this at all,” Sparks adds.

The new documentary includes footage of this shocking moment, showing Attenborough pressed to the ground as a young gorilla relaxes on top of him, seemingly unbothered by the man in their midst.

Decades later, Attenborough still has vivid memories of that unbelievable encounter that lasted at least 10 minutes.

“I was simply transported,” he says of the remarkable moment.

Since then, Attenborough has had countless transportive moments, but this may have been the one that launched them all.

To learn more about Attenborough’s time with the gorillas, and to celebrate his 100th birthday, watch Life on Earth: Attenborough’s Greatest Adventure, premiering on May 6 on PBS at 8 p.m. ET.