"I looked at that fossil in that rock and knew exactly what he had found," his father recalled.
He had found a clavicle, a collar bone.
"That clavicle alone would've been a great find. It would have been enough for me certainly. You know most people who do what I do, do what Job do, go through their entire careers and never find even a single piece," Berger said. "I had found a few dozen fragments, I mean fragments, before this."
It gets even better: on the other side of the rock there was a jawbone and a tooth - a canine.
"That was amazing," Kibii said. "We would turn to the clavicle. We high-fived. We turned to the canine. Because we knew that we have hit a jackpot."
Hitting the jackpot, without even digging. Why was it so easy? A hundred years ago miners blasted these caves, scattering rocks and unearthing fossils, fossils including a skull.
Berger and Simon stood in a pit where Berger pointed out exactly where he found the skull. "It was lying on its side, sticking out of the wall. Its foot is still in the rock just up at the top, there," he explained, pointing to it.
Berger sent the rocks to his lab at the University of the Witwatersrand, where workers began painstakingly extracting the fossils. The dating of the rocks showed they were around 1.9 million years old. Analysis of the bones revealed that what the scientists had in their hands was not one skeleton but two: a nine-year-old boy and a 30-year-old woman.
"I think it really is a most remarkable set of finds, and particularly the quality. I don't think we've found anything like this before," Richard Leakey told Simon.
When Leakey, the world's most renowned paleoanthropologist, examined the bones, he said they were almost too much to digest. "It was a wow experience," Leakey recalled. "I mean, there's a lot of stuff there. And it's spectacular. It is so full of information, so much data, that I had to say to him after an hour, I said, 'Lee, I've had enough.'"
"Lee is still finding bones in that cave. Has he struck a gold mine?" Simon asked.
"Yes, he's got a treasure trove. No question, a treasure trove," Leakey said.
Back at the site, Berger and a team of geologists were trying to figure out exactly what had happened 1.9 million years ago. What had these creatures been doing?