My first thought was, This is unbelievable. There was my childhood dream right at my feet. I was lucky as a kid to meet my mentor, an anthropologist who let me use his library. At age 13, I had an epiphany after reading Thomas Henry Huxley’s book Evidence as to Man’s Place in Nature. It predicted that someday someone will find an ape more humanlike or a man more apelike. That someone turned out to be me.

Lucy was the ape who stood up. She walked like we do. We found the pelvis and leg bones that look a lot like ours. But her face was very apelike, and her brain was the size of an orange. We now have hundreds of specimens of Lucy’s species, Australopithecus afarensis. They didn’t have symbolic language or art. But they were living together, which is an example of cooperation, a key factor for humans’ survival.

She reshaped our understanding of the origins of the human family tree. My hypothesis, which remains the predominant view, was that Lucy’s species was the last common ancestor to other branches of her species that went extinct and the branch that led to our species, Homo sapiens. Lucy caught the public’s imagination because she was a prehuman they could visualize. We recovered 40 percent of her skeleton.

That was a very emotional moment for me. I knew in 1974 it would be important for my career but not how enduring it would be. Now being 80, I’m grateful for being alive to see how significantly that discovery influenced the last 50 years.

I have a romantic view ... of the early days, being in remote camps in the middle of the desert, sitting around a table at night with little kerosene lamps. Today I don’t want to live in a tent for two months in the middle of the desert. But looking back at my diaries, I don’t remember ever complaining.

It’s the best. I married a woman named Robin who is a true partner. She’d written me a letter and later helped me through some writing challenges. But it was a number of years before I actually met her for dinner. It was like, Wow! Where have you been my whole life? It was definitely a spark.

We were on a safari in southern Kenya with close friends, having a picnic under a beautiful acacia tree. And I walked over to Robin and asked her to marry me. She said yes. Besides our friends, no other people were around, but a small herd of zebras stopped by. We’ve been happy every day since.

I wake up loving every day. I feel we’ve been given this incredible opportunity to be alive. I used to shock my students by telling them, “You’re the lucky ones, because you’re going to die.” Then I’d explain, “The only reason you’re going to die is because you were born. A few genes different and you would not be you.” We all need to embrace this gift of being born human, and find our passions.

People say even the dinosaurs went extinct. Well, they didn’t have a choice. We do. We have the smartest organ—our brain—that we know of in our solar system. We have the technological complexity to solve a lot of problems. But as a species, we are overly focused on ourselves. I call us “Homo egocentricists.” We need to understand our place in the natural world and cooperate to preserve this precious planet.

The Lucy spacecraft will explore a group of Trojan asteroids, mysterious space rocks trapped in Jupiter’s orbit that hold vital clues to the origins of our solar system. Last November, Lucy successfully flew within 270 miles of an asteroid called Dinkinesh—Lucy’s Ethiopian name—that’s 300 million miles away. And discovered Dinkinesh has a moon. I mean, wow!

Well [laughs], I can’t say I did either.

Yes. I’ll probably be with the pilot steering the spacecraft in Colorado. My discovery of an early ancestor who walked upright came just a few years after Neil Armstrong walked on the moon. Now the Lucy mission and the James Webb Space Telescope are unlocking the history of our cosmos. Future generations will determine how long Homo sapiens continues to be the most extraordinary species we know of in the universe.