PROLOGUE

Slipping between the loose, rusty wires of the game fence, I paused to let my son, Matthew, through. I pressed my foot down on the lowest wire, pushing just hard enough to create a gap for Matt and my young Rhodesian ridgeback, Tau. I’d barely made much of a space before they darted through.

With me on the other side was Job Kibii, a slim, Kenyan paleoanthropology postdoctoral student; we both smiled at our companions’ youthful energy. I pulled the wires wider for Job, and we turned toward a small cluster of wild olives and white stinkwood trees. Matt and Tau were already in the trees’ shade, a few dozen meters away.

“That’s it,” I said, gesturing toward the ring of trees. “I can’t believe I didn’t find it earlier.”

Job nodded in agreement as he surveyed the rolling landscape of the Cradle of Humankind. The Cradle, a large area designated by UNESCO as a World Heritage site, is not far from my home in Johannesburg, South Africa. Just a few dozen kilometers outside a metropolis of more than five million people, this place is a world away: a pristine wilderness, home to zebras, antelopes, giraffes—even leopards and hyenas. It is also one of the most famous areas for fossil discovery on the planet. Most of that fame was established during a golden age of paleoanthropology, from the mid-1930s up to the 1970s, when scientists discovered caves full of fossil bone deposits going back three million years.

I had known this area for 18 years; for the past several months, I had been conducting a new survey of fossil sites here. It was the morning of August 15, 2008—a typical winter morning on the Highveld: crisp, cool, and cloudless. I had no idea that in just a few minutes, my life was going to change forever, thanks to a discovery made by a boy and a dog.

I WAS WORKING TO confirm a hunch, originating with a 10-year-old computer error that had set me in motion a few months before. The previous December, I had started surveying this terrain I knew so well with Google Earth, the new satellite image–viewing software. Of course, the first thing I looked at was my house (where, thank goodness, the satellite hadn’t caught me lounging by the pool). Then I checked the sites I already knew. Google Earth was new, but I had been surveying the Cradle using handheld global positioning system (GPS) units since 1998. I could practically recite the lat-long positions for fossil sites from memory.

I started with Gladysvale, a cave situated nearly in the center of the Cradle where I had first worked in 1991 and where I had found two hominin teeth. Hominins—also called hominids—are members of the human family tree, which includes all the extinct species more closely related to people than to any great apes living today. Hominin bones are precious pieces of evidence for our origins.

I had expected we would find more hidden treasures among the tons of rock and sediment we excavated during the next decade and a half of exploration at Gladysvale. But in the long run, although my colleagues, students, and I found the remains of thousands upon thousands of antelopes, we found only fragments of one or two hominins. Still, I loved the place, loved the feeling of being in the bush. I had even loved looking at every one of those antelope bones, even if they weren’t from hominins.

With Google Earth up on my computer screen, I punched in Gladysvale’s GPS coordinates. I remember seeing the satellite image leap upward from my house, way up into the sky, swing northwest, and then rapidly zoom down onto the Cradle. I could see the familiar hills, streams, and valleys around Gladysvale becoming sharper and sharper. But as the image blurred to huge pixels, I saw there was something wrong. This wasn’t Gladysvale: It was actually the valley next to Gladysvale—a spot almost 300 meters away! I typed in the coordinates of another place I had worked, the Cooper’s Cave site. Again, the image leaped into the air, this time moving southwest. Again, the position was wrong. I entered location after location, and none was correct. I was horrified. Had I recorded the GPS coordinates incorrectly? Had I been working with the wrong numbers for almost a decade?

I soon learned that in the 1990s, before GPS was perfected for public use, the handheld units were primitive and somewhat error-prone—in part because they were designed for military use, with deliberate error built in to confound potential enemies. It meant that to use Google Earth to view all those sites I knew—more than 130 altogether—I had to relocate their positions manually.

That left me trawling the landscape on the computer screen. At first I felt frustrated—years of work had to be corrected—but slowly I began to recognize that this mistake was leading me to a new way of looking at things. I began to understand what caves and fossil sites really looked like from overhead. Some were marked by clusters of trees, some by disturbances in the ground. Sometimes they were clustered, often in linear patterns that I realized must mark the geological faults that had allowed caves to form. Slowly the prospect emerged that the Cradle of Humankind might contain more sites than anyone had previously thought: in the bedrock, underground.

The bedrock underlying the quarter million hectares of Cradle land is made up of dolomitic limestone. Extremely hard and resistant to erosion, it makes a rocky land surface with outcrops, cliffs, and exposed areas of rock that slowly weather in a pattern that the locals call “elephant skin rock.” Cracks and faults within the dolomite allow water to seep downward, dissolving the rock and creating cavities and fissures over millions of years. Through those millennia, animals have used those caves, sometimes leaving bones—their own bones or those of their prey. As the water percolates through, these bones can get stuck together with gravel, dirt, and rocks, resulting in a jumbled, cemented mass of fossil bone and rock called breccia. The breccias of the Cradle have given rise to many of the world’s most important fossil discoveries relating to human evolution.

In February 2008, I had begun to verify my hunch about undiscovered sites, ground-truthing the idea by good old-fashioned walking. As I did the footwork, I found that about one in 10 sites held something worth mapping: pretty good odds in the fossil-finding business. By July 2008, I had discovered almost 600 previously unrecognized cave and fossil sites—and this in the most explored area on Earth for these types of sites!

The site that Matt, Job, and I were exploring that August day in 2008 was one I had settled on two weeks earlier. What drew me to it was a grove of trees: Wild olive and white stinkwood trees had become my new guide to the Cradle geology. These species often grow near cave openings, I had come to realize, because cracks in the dolomite allow water to penetrate deep into the rock, creating a pathway for the trees’ roots through the water-starved dry season.

This grove of trees looked no different from the others. It was right near a road I had driven hundreds of times before. But there was an old miners’ track that I had somehow missed, and that predicted a cave nearby. Miners around here wouldn’t have been looking for gold. They would have been finding limestone-rich caves, blasting out deposits of calcite rock, and baking it in kilns to produce quicklime, which is then used to make concrete and extract gold from ore found elsewhere in South Africa. The lime miners had worked the landscape extensively, but more recently I’d combed it ceaselessly for fossils. I had hiked over practically every inch of it in those years—it was a place I loved, a place that had been my laboratory for much of my research. I knew it probably better than anyone alive.

We were just over the hill from Gladysvale, the cave where I had tried—and so far, failed—to make a big hominin find. Over the years, I had looked at hundreds of little fossil sites like this one, turning over rocks and examining the small cross sections of broken fossil bones sticking out of them. Now, standing in front of yet another potential site, I didn’t get my hopes up, but I was always ready to explore. “Shall we take a look?” I asked, tilting the brim of my hat back. It was a rhetorical question—seeing what this little site might have to offer was why we were there.

Walking toward the grove of trees, I kept my eyes on the ground, scanning for any anomaly different from the native rock. Tiny white chips of lime were scattered about, marking the miners’ trackway like breadcrumbs in a fairy tale. Large blocks of breccia lay by the track, blasted out and then tossed aside. We passed more and more of them as we approached the main pit left behind by the mining operation. I picked up a rock about the size of a basketball and gestured to Job to come take a look. Matthew and Tau looked on curiously.

“This is the first one I found.” I turned the rock so Job and Matt could see. My fingers traced an orange bone embedded in chocolate brown rock.

“An antelope metapodial?” asked Job.

I nodded. It was the fossilized leg bone of an antelope. Job was an expert in fauna—animals and their fossil bones—and had come with me that morning to decide whether this deposit would contribute to his own research.

“They are always antelopes,” I said, shaking my head with a grin. So many antelopes, so few hominins.

I knew people who had made big discoveries—discoveries that had struck their worlds like lightning. I wasn’t one of those people. Still, I counted myself lucky. At age 42, I was a successful scientist with a very good run of fieldwork and research papers. Over 19 years of searching, I had found maybe a dozen bits and pieces of hominin fossils among thousands of other animal fossils.

Paleoanthropology—the search for human origins—is a tough, competitive, and unforgiving field. A colleague of mine once joked that we are probably the only branch of science that has more scientists than objects to study. That wasn’t too far from the truth. In a field of such scarcity, even a small find—a jawbone, even a single leg bone—could make a career.

But now, as we stood at the edge of the pit, I had my doubts about the quality of this site. For one thing, it was too small—nothing like the big sites of the Cradle that had yielded the important hominin fossils. The odds were tiny. Maybe one in hundreds of thousands of fossils will be a hominin bone, and so you need a lot of fossils to start. This tiny pit couldn’t possibly contain many thousands of fossils, and so it wasn’t a very good bet. But Matt was eager, so I was willing.

The miners’ work had been hasty. Marks on the walls of the pit indicated where they had put in dynamite charges, blasting out brown chunks of breccia with angular, freshly broken edges, scattered under and around the trees. The miners hadn’t put very much effort into digging here. They left only a handful of blast holes before moving farther up the valley.

“OK, go find fossils,” I said to Job and Matt. “If you find anything, let me know. We’ll see what this site has to offer.”

Matt and Tau bounded off into the high grass away from the pit. I imagined that they had decided to chase antelopes instead of hunting fossils today. I smiled as I watched them run off, Tau in the lead.

“I think the miners might have been just blasting to get material to pack the road,” I said to Job. I gestured to the smaller fragments that seemed deliberately placed among the rougher bedrock of the trackway. “It doesn’t look like there was enough lime for them to stay here very long.”

Matthew’s voice rang out.

“Dad, I found a fossil!”

He was some 20 meters away, over in the tall grass, where there couldn’t possibly be any fossils. I glanced over at Job and shrugged. “Let me go see what he’s got,” I said.

Matt was kneeling next to a broken tree stump. A jagged, charred hole showed where lightning had once struck it. He was holding a rock about the size of a rugby ball. He looked toward me, beaming. Tau was lying down beside him, panting, ears perking as I walked over.

Matt was too far off the site, too far away from that pit, to have found anything very important. Even if it was a fossil, it was probably just a piece of antelope. But he was my nine-year-old son, and I had always encouraged curiosity—and an eagerness to go fossil hunting—in both Matt and my daughter, Megan.

Five meters away, my eyes focused on Matt’s rock, and I felt time stop.

Sometimes people who have been in a car crash describe their memory of the event as being like a black-and-white silent movie. That’s the way I remember that moment now. A bone stuck out of the rock. I knew instantly what it was: the clavicle, or collarbone, of a hominin. I knew that fossil shape—I had done my Ph.D. research on this bone. Still, I doubted myself. But as I took the rock from Matt and stared at the little S-shaped piece of bone, I thought, “What else could it be?”

I turned the rock over to get a better angle. There was a hominin canine tooth and part of the jaw, as well as other bones. This was not just any hominin. And, at the very least, there were several parts of the skeleton embedded in this chunk of rock.

Matt says I cursed. I don’t remember. Whatever I said or did, I knew for sure that both his life and mine were about to change forever.