![]() Brains do not fossilize, but as the brain grows and expands before and after birth, the tissues surrounding its outer layer leave an imprint in the bony braincase. Together, these characteristics are important for human cognition and social behavior, but their evolutionary origins remain unclear. For example, compared with chimpanzees, modern human infants learn longer at the expense of being entirely dependent on parental care for longer periods of time. The brains of modern humans are not only much larger than those of our closest living ape relatives, they are also organized differently, and take longer to grow and mature. However, a comparison of infant and adult endocranial volumes nevertheless indicates more human-like protracted brain growth in Australopithecus afarensis, likely critical for the evolution of a long period of childhood learning in hominins. afarensis more similar to that of chimpanzees or that of humans?Ĭontrary to previous claims, the endocranial imprints of Australopithecus afarensis reveal an ape-like brain organization, and no features derived towards humans. These data shed new light on two questions that have been controversial: Is there evidence for human-like brain reorganization in Australopithecus afarensis? Was the pattern of brain growth in A. Several years of painstaking fossil reconstruction, and counting of dental growth lines, yielded an exceptionally preserved brain imprint of the Dikika child, a precise age at death, new endocranial volume estimates, and previously undetected endocranial features of well-known Australopithecus fossils. ![]() In addition, seven other well-preserved fossil crania from the Ethiopian sites Dikika and Hadar were scanned using high-resolution conventional tomography. With the help of this state-of the-art technology researchers can reveal the age at death with a precision of a few weeks. To study brain growth and organization in Australopithecus afarensis the researchers scanned the fossil cranium of the Dikika child using synchrotron microtomography at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. "Our new results show how their brains developed, and how they were organized," adds Alemseged. They walked upright, had brains that were around 20 percent larger than those of chimpanzees, may have used sharp stone tools," explains senior author Zeresenay Alemseged from the University of Chicago, who directs the Dikika field project in Ethiopia, where the skeleton of an Australopithecus child was found in the year 2000. "Lucy and her kind provide important evidence about early hominin behavior. The species Australopithecus afarensis inhabited East Africa more than three million years ago, and occupies a key position in the hominin family tree, as it is widely accepted to be ancestral to all later hominins, including the human lineage.
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