Forty years ago yesterday, November 24, 1974, paleoanthropologist Donald Johanson found in Ethiopia what’s arguably the most famous and important fossil of a human ancestor: Lucy. Last month, at the ScienceWriters2014 meeting in Columbus, Ohio, Johanson talked about the moment he laid eyes on Lucy.

“On that eventful day in 1974 I was out, with a graduate student, Tom Gray, and we were walking back to our Land Rover to go back to camp to enjoy a swim in the river with the crocodiles and enjoy a nice little lunch. And I am always looking at the ground. I find more quarters by parking meters than anybody I know, I think. And you know how it is you find what you’re looking for, right?

“Because a year before the discovery a geologist had left his footprints four-to-five feet away from the skeleton, because he was looking for rocks. I was looking for bones. And I found a little piece of elbow, that little hinge that allows us to flex and extend our arm. And I knew from my studies of osteology, of comparative anatomy and so on, that this had to be from a human ancestor.

“And I as looked up the slope, I saw other fragments eroding out. And we recovered over a two-week-long excavation operation roughly, not counting hand and foot bones, 40 percent of a skeleton. And this was important because first of all it broke the three-million-year time barrier. All the fossils older than three million years at that point in the history of paleoanthropology would fit in the palm of your hand…we didn’t know it was a new species really until a few years later when we finally published in 1978 the name Australopithecus afarensis.”

For more, check out the blog item on our Web site by Scientific American’s Kate Wong who, with Johanson, co-authored the book Lucy’s Legacy. Kate’s blog is titled The Fossil That Revolutionized the Search for Human Origins: A Q&A with Lucy Discoverer Donald Johanson.

—Steve Mirsky

[The above text is a transcript of this podcast.]