Fossil Hunter

Zeray Alemseged wants to know about your ancestors—but not your parents, your grandparents, or even your great-grandparents. He prefers to look back thousands of generations, to the ancestors of all humankind.

Alemseged is a paleoanthropologist, a scientist who studies early humans and their predecessors, at the University of Chicago. He returns to his native country of Ethiopia to hunt for fossils every year. In 2000, he made a remarkable discovery: the nearly complete skeleton of a 2½-year-old girl who died 3.3 million years ago. She belonged to the species Australopithecus afarensis.

Alemseged named the fossil Selam, which means “peace” in several Ethiopian languages. It’s the oldest fossil of a child ever found. Alemseged and other scientists have been analyzing the remains ever since. He spoke to Science World about what his unique find can teach us about humanity’s past.

Humans are the result of millions of years of evolution. Paleoanthropologists like myself try to find fossil evidence that helps us figure out how we became the widespread species we are today. Paleoanthropology is a scientific way to answer a fundamental question: Where do we come from?

I work in an area called Dikka in the Afar depression. Today it’s a barren desert. But 3 million to 5 million years ago, it was covered with trees, rivers, and lakes. Our ancestors lived there along with many other species. These early ancestors were primates, an order of animals that also includes monkeys, apes, and modern humans.

When ancient animals, including our ancestors, died in this area, they sometimes fell into lakes and rivers. They were covered in layers of sediment, like dirt and mud. Over millions of years, minerals seeped into the bones, changing them into fossils. Later, earthquakes brought old sediments to the surface, along with the fossilized remains that were buried a long time ago.

My team had been working in the Afar depression for many years. We’d encountered all sorts of animal fossils—hippos, monkeys, you name it. Then one afternoon we noticed something shiny sticking out of the dirt. It was a cheekbone just sitting on the surface. It didn’t take long to find the rest of the face and a portion of the jaw. Looking at the flat forehead and small teeth, I could tell that it belonged to a child human ancestor.

I carefully wrapped the specimen and put it in my backpack. It took five years of sifting through dirt to find the rest of the skeleton. Then we spent 12 years preparing it, using a dental instrument under a microscope to remove sand that had encased it.

A. afarensis was at the cusp of being human. They had a protruding face similar to that of our closest living relatives, chimpanzees. But their pelvis, or hip bone, was human-like. That tells us that they were adapted to walk upright, like we do. Selam’s skeleton shows that they also climbed trees sometimes. The way her shoulder is oriented and features on the bones that suggest how the muscles were attached indicate that she was a capable climber. Her big toe could move more than ours, which would help her grip branches. We think that young A. afarensis ate fruits and leaves and hid in trees from predators.

Humans have always been curious about their origins. Rather than asking about my personal origins, which I know are in Ethiopia, I ask about the origins of all 7 billion people in the world. It makes me feel very empowered and also humbled. People today have different eye shapes, hair texture, or skin colors, but it only takes a moment of reflection on our common ancestors found in Africa to realize that we are all the same.