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Lucy's Baby [Preview]

An ancient infant skeleton yields new insight into how humans evolved to walk upright
Bundle of Joy

It was the afternoon of December 10, 2000, when fossil hunters led by Zeresenay Alemseged, now at the California Academy of Sciences in San Francisco, spotted the specimen. Only part of its tiny face was visible; most of the rest of the skeleton was entombed in a melon-size block of sandstone. But “right away it was clear it was a hominin,” Alemseged recollects, noting the smoothness of the brow and the small size of the canine teeth, among other humanlike characteristics. Further evaluation, however, would have to wait until the fossil was cleaned—a painstaking process in which the cementlike matrix is removed from the bone almost grain by grain with dental tools.

It took Alemseged five years to expose key elements of the child's anatomy; he continues to analyze bones revealed since then. Still, the find has already surrendered precious insights into a species that most researchers believe gave rise to our own genus, Homo. Alemseged and his colleagues described the fossil and its geologic and paleontological context in two papers published in 2006 in Nature. And at a press conference held in Ethiopia to announce the discovery, they christened the child Selam—“peace” in several Ethiopian languages—in hopes of encouraging harmony among the warring tribes of Afar.

The skeleton, judged to be that of a three-year-old girl, consists of a virtually complete skull, the entire torso, and parts of the arms and legs. Even the kneecaps—which are no larger than macadamia nuts—are preserved. Many of the bones are still in articulation. Hominin fossils this complete are incredibly rare, and ones of infants are rarer still because their bones are that much more fragile. Indeed, the next oldest skeleton of a juvenile that is comparably intact is a Neandertal baby dating to around 50,000 years ago.

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