UPFRONT | Roundup RESEARCH Take 5 Ancient fossil reveals origins of human spine Analysis of a 3.3 million-year-old fossil skeleton reveals the most complete spinal column of any early human relative, including vertebrae, neck and rib cage. The findings, published recently in the Proceedings of the National Academy of Sciences, indicate that portions of the human spinal struc-ture that enable efficient walking motions were established millions of years earlier than previously thought. The fossil, known as “Selam,” is a nearly complete skeleton of a two and a half year old child discovered in Dikika, Ethiopia in 2000 by Zeresenay (Zeray) Alemseged, pro-fessor of organismal biology and anatomy at the University of Chicago and senior author of the new study. Selam, meaning “peace” in the Ethiopian Amharic language, was an early human relative from the species Australopithecus afa-rensis – the same species as the famous Lucy skeleton. In the years since Alemseged discovered Selam, he and his lab assistant from Kenya, Christopher Kiarie, have been preparing the delicate fossil at the National Museum of Ethiopia. They slowly chipped away at the sandstone surrounding the skeleton and used advanced imaging tools to further analyze its structure. “Continued and painstaking re-search on Selam shows that the general structure of the human spinal column emerged over 3.3 million years ago, shedding light on one of the hallmarks of human evolution,” Alemseged said. “This type of preservation is unprece-dented, particularly in a young indi-vidual whose vertebrae are not yet fully fused.” Many features of the human spinal column and rib cage are shared among primates. But the human spine also reflects our dis-tinctive mode of walking upright on 8 Canadian Chiropractor July 2017 two feet. For instance, humans have fewer rib-bearing vertebrae – bones of the back – than those of our closest primate relatives. Humans also have more vertebrae in the lower back, which allows us to walk effectively. When and how this pattern evolved has been unknown until now because complete sets of vertebrae are rarely preserved in the fossil record. “For many years we have known of fragmentary remains of early fossil species that suggest that the shift from rib-bearing, or thoracic, vertebrae to lumbar, or lower back, vertebrae was positioned higher in the spinal column than in living humans. But we have not been able to determine how many vertebrae our early ancestors had,” said Carol Ward, a curator’s distinguished professor of pathology and ana-tomical sciences in the University of Missouri School of Medicine, and lead author on the study. “Selam has provided us the first glimpse NUMBER CRUNCHING into how our early ancestors’ spines were organized.” To be analyzed, Selam was taken Fast facts about chiropractic in Alberta to the European Synchrotron Radiation Facility in Grenoble, France, where the research team used high-resolution imaging tech-nology to visualize the bones. The scans indicated that Selam had the distinctive thoracic-to-lum-bar joint transition found in other Albertans who have received chiropractic treatment fossil human relatives, but the specimen is the first to show that, like modern humans, our earliest ancestors had only twelve thoracic vertebrae and twelve pairs of ribs. Longest serving active member of the ACAC That is fewer than in most apes. The study, “Thoracic Vertebral Count and Thoracolumbar Transition in Australopithecus afa-rensis,” was supported by Margaret and Will Hearst, the National Science Foundation and the European Synchrotron Radiation Facility. Provincial chiropractic utilization rate Number of active chiropractors – Newswise West side story 65% 24 % 60 YEARS Illustration: Brian Fray 1070 www.canadianchiropractor.ca
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