Current Expedition: Afar Depression, Ethiopia
Dikika Research Project
Dr. Zeresenay “Zeray” Alemseged studies the origin and evolution of early human ancestors, and the environmental factors that influence their evolution. His objective: to unearth and analyze clues to their biology and behavior and to identify milestone evolutionary events that ultimately led to the emergence of modern Homo sapiens.
In 2006, Dr. Zeray Alemseged made an indelible mark in the field of anthropology when he reported finding the nearly complete fossilized remains of a 3.3 million-year-old Australopithecus afarensis child in his native country of Ethiopia. Known as the “world’s oldest child,” it is the most complete skeleton of a human ancestor discovered to date and represents a major advancement in our understanding of human and pre-human evolution.
Alemseged was born in the historic town of Axum, in northern Ethiopia. A curious kid, he often snuck into school before he was old enough to attend, just for the joy of learning. After earning a degree in geology, Alemseged was assigned to work in Ethiopia’s National Museum, home to the famous 3.2 million-year-old A. afarensis fossil “Lucy,” which revolutionized the study of human evolution when Donald Johanson unearthed it in 1974. Inspired by his experience there, Alemseged decided to pursue a Ph.D. in anthropology at the University of Paris. He ultimately returned to Ethiopia in search of more evidence about our early hominin ancestors.
Following a hunch, Alemseged set his sights on the Pliocene site of Dikika—an isolated region of the Afar Depression about 400 miles from his hometown—as an optimal place to look for new fossils during his first field season. Other scientists had historically avoided the area. A centuries-old tribal conflict made it too dangerous to work in, but Alemseged succeeded in convincing both sides to allow him to conduct research there.
Thanks to his perseverance and negotiation skills, Alemseged’s hunch paid off on December 10, 2000. While surveying a hillside and sifting through the dirt and rubble, he and his team discovered the fossilized skeleton of a 3.3 million-year-old baby girl. To find any human remains that old is remarkable; to find the remains of a 3-year-old child, whose fragile bones would have been very attractive to scavengers, was truly extraordinary.
Like “Lucy,” the Dikika child was a member of the species A. afarensis. Nicknamed “Selam,” which means “peace” in several Ethiopian languages, the fossil was excavated over the course of four field seasons. Selam is not only the most complete ancient infant unearthed so far, she is also perhaps the most diagnostic example of her species. Unlike Lucy’s more famous but less complete skeleton, Selam’s remains include fingers, a foot, a full torso, and—most importantly—a face.
When Alemseged officially announced the discovery of Selam to the scientific community, the story garnered news coverage around the globe and personal congratulations from the President of Ethiopia. In the years since, Alemseged has been making headway on a long list of questions that Selam’s fossilized bones can help answer about the anatomical, behavioral, and developmental evolution of early human ancestors and their divergence from the apes.
One of the first topics Alemseged tackled was related to locomotion—how Selam and her kin moved around 3.3 million years ago. The hip, leg, and foot bones of Australopithecus afarensis indicate that Selam’s was an upright-walking species, but the point in time when our ancestors abandoned tree-climbing behavior—a key milestone in human evolution—remains a subject of debate. Prior to Selam's discovery, no intact shoulder blades were available to study.
“Because shoulder blades are paper-thin, they rarely fossilize,” Alemseged said. “When they do, they’re almost always fragmentary. Finding a pair of shoulder blades completely intact and attached to a skeleton of a known and pivotal species was like hitting the jackpot.”
In a 2012 study published on the cover of the journal Science, Alemseged and his colleagues found Selam’s fragile scapulae to be quite ape-like. This finding suggested that A. afarensis was still a capable climber despite its bipedal lower body, which means our ancestors may have abandoned tree-climbing much later than many researchers had previously suggested.
Alemseged continues to study Selam. He also serves as head of the Dikika Research Project, which he founded in 1999, conducting annual field work in Dikika and neighboring regions of the Afar region in search of additional evidence for our ancestors’ evolutionary journey.
We wouldn’t be where we are today without tools. Long before refrigerators and cars, early human technologies consisted of sharp flakes of stone, which our ancestors began using and making tools from far earlier than previously thought. In 2010, an international team of scientists led by Alemseged discovered evidence in the Afar region of Ethiopia that Australopithecus afarensis was using stone tools and eating meat roughly 3.4 million years ago, pushing the timeframe of human tool use and manufacture back by nearly a million years.
The team found fossilized bones bearing marks that may have been caused by stone tools used to carve meat, along with what appears to be percussion marks made when breaking bones to extract marrow. Previously, the oldest known evidence of butchering with stone tools came from Bouri, Ethiopia, where several cut-marked bones dated back to 2.5 million years ago.
“Tool use fundamentally altered the way in which our early ancestors interacted with nature, allowing them to eat new types of food and exploit new territories,” Alemseged said. “It also led to tool making—a critical step in our evolutionary path that eventually enabled advanced technologies such as airplanes, MRI machines, and iPhones.”
Case in point is the modern archaeologist's toolkit, a juxtaposition of simple and high-tech instruments, each of which plays a crucial role. In the field, where roads, water, and power supplies are few and far between, hand-held GPS devices have transformed the data collection process. These high-tech tools integrate many data points—from location coordinates and notes about the geologic setting to photos taken with a built-in camera—into one “geodatabase” that can sync with a laptop at the end of each day, making documentation more efficient and complete. For some tasks, however, nothing beats a delicate touch. Alemseged still sifts through dirt and sand manually, using brushes and picks to carefully remove sediment from fragile objects.
In his lab, Alemseged needed more than 10 years to remove Selam’s skeleton from its dense sandstone encasement grain by grain with a microscope and a dental drill. Once freed, the skull was taken to a diagnostic center in Nairobi, Kenya for a high-powered CT scan. The imagery revealed a mixture of deciduous—another name for baby teeth—and permanent teeth, which provided valuable clues to Selam’s sex and her age at death without compromising the specimen’s integrity. Technology has advanced since the original CT scans, and synchrotron techniques with super-resolution microscopes now allow for an even closer look, revealing fine details like growth lines in fossilized teeth. Originally developed for materials science applications, these specialized microscopes are only available at a handful of sites worldwide.
The evolutionary road to modern Homo sapiens took many twists and turns, as Academy visitors can see in Human Odyssey, an exhibit Alemseged curated located in the Tusher African Hall. The following milestones represent some of the major turning points along that journey:
About 6 – 7 million years ago
The earliest human ancestor diverges from the ape family and begins the transition toward walking upright. Genetic evidence confirms that our closest living relative is the chimpanzee, with which we share more than 98 percent of our DNA.
About 4 million years ago
Habitually walking members of the genus Australopithecus make their first appearance in the fossil record. Large teeth with thick enamel allowed these hominids to begin eating tubers and other abrasive foods for the first time. Tool use may have emerged with this genus.
About 2.5 – 3 million years ago
Our ancestors begin making and using stone tools to eat meat. Animal fossils from this time period show evidence of butchering.
About 1.5 – 2 million years ago
Homo erectus emerges for the first time. With long legs and short arms, this early human is well adapted to walking long distances and begins to cover a much larger range, eventually becoming the first hominid to spread out of Africa and onto other continents.
About 800,000 years ago
Although it's difficult to document when our human ancestors first began controlling fire, scientists believe it to be around this time.
About 130,000 – 195,000 years ago
Humans (Homo sapiens sapiens) are now fully modern. Compared to earlier members of the genus Homo, modern humans have larger brains and lighter skeletons.
Current Expedition: Afar Depression, Ethiopia
Dikika Research Project
Learn more about Dr. Alemseged's research, publications, and current projects by visiting the research side of our website, home to the Academy's Institute for Biodiversity Science and Sustainability.
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