![]() In 2010, paleoanthropologist Lee Berger of the University of the Witwatersrand and his team announced a new species from South Africa. Not long after the discovery of late hominins with “primitive” pelvic structures came the discovery of a “modern” structure in an earlier species. erectus) known to have a larger brain than Lucy and her kin. To deepen the mystery, this time it’s found in a species ( H. If the Gona pelvis is ultimately classified as Homo erectus, the implication is that we have a fossil mystery on our hands: Now there are two species of Homo that have australopith-looking ilia. erectus at all, but no clear consensus has been reached, owing to the lack of cranial evidence. Some experts argue that its small size and Lucy-like ilia mean that it’s not H. The Gona pelvis has a shorter ischium than Lucy or the Liang Bua fossil, but it still has the wide, platelike ilium seen in earlier human ancestors. In contrast, the Gona pelvis is short and wide, and also of a much smaller individual. When found, this male pelvis was crushed and incomplete, but by using the skeleton of a modern human boy for reference, paleoanthropologists Alan Walker of Pennsylvania State University and Christopher Ruff of Johns Hopkins School of Medicine made an initial reconstruction, which revealed a tall and narrow pelvis. erectus had been the 1.6-million-year-old specimen dubbed Nariokotome Boy, discovered near Lake Turkana in Kenya by Kamoya Kimeu of the National Museums of Kenya. Prior to this discovery, the fossil pelvis best known from H. Today most paleoanthropologists accept that these fossils are not pathological humans but are indeed their own species now the argument focuses on how closely they are related to other hominins and how they got to the island of Flores. Pelvic anatomy of this kind had never before been seen in the genus Homo, and initially some argued that the surprising anatomy was the result of a pathology rather than indicating a new species. They described Homo floresiensis, whom we now know lived around 100,000 years ago, as a small-bodied member of our genus the media quickly dubbed them “hobbits.” Although the skeletal fossils generally appear similar to humans (thus classifying them in the genus Homo), the pelvis looks a lot like Lucy’s: The ilium sticks out at an angle, forming a plate instead of a bowl shape, and the ischium is extremely long. In 2003, Peter Brown and Michael Morwood, both affiliated with the University of New England in Armidale, Australia, published a paper with their colleagues on a newly discovered human relative from Liang Bua Cave, on the island of Flores, Indonesia. This handful of somewhat-complete pelvic fossils in the hominin record seemed to support the concept of pelvic evolution as a process that moved in only one direction, with later hominins-including us-having a different pelvic shape (due to our increasing brain size) from the earlier, smaller-brained species. Up until about 15 years ago, the best-known pelvic remains of Australopithecus were two species with wide, platelike ilia and long ischia, and the only known pelvis from Homo erectus was one with narrow, bowl-shaped ilia and short ischia. Yet few pelvic fossils from that period have been uncovered. Plenty of cranial fossils have been unearthed that show brain size started increasing around two million years ago, the time that our genus, Homo, emerged. ![]() ![]() Plausible as this model may be, however, it does not explain the pelvic evidence in the fossil record. One apparent result of such adaptations is the set of skeletal features that distinguish female pelvises from male ones, irrespective of body size. Paleoanthropologists have suggested that as birth became more complex, owing to an increase in brain size, the pelvis-especially the female pelvis-adapted to expand the birth canal. The exact shape differs subtly from one fossil species to another. Some version of this squatness is seen in every hominin pelvic fossil, although no two are identical. By contrast, in hominins the pelvis forms a squat, sturdy base that supports and balances the weight of the upper body when walking or standing on two legs without requiring much effort. ![]() The pelvis of a chimpanzee extends across the lower back to support the lower body when the animal is swinging through the trees for a chimpanzee to walk on two legs, however, requires a lot of effort and energy. Paleoanthropologists generally agree that when hominins began walking on two legs, something we’ve been doing for more than three million years, the shape of the pelvis changed to accommodate our bipedal gait. My research focuses on the evolution of the pelvis, an important part of our evolutionary story because the pelvis of hominins differs dramatically from that of the chimpanzee-and possibly, therefore, from that of our last common ancestor.
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