Together with the previously discovered bones of the same individual – nicknamed “Isa”, which is Swahili for keeper – the fossil remains are one of the most complete lower bodies ever discovered in the early hominid record and indicate that this How human is the relative would have moved through the world.
Researchers said the newly studied lower limb fossils were a missing link that proved that early hominins used their upper limbs to climb like apes, and their lower limbs to walk like humans.
The fossils were first discovered in 2015 during excavations of a mining trackway running next to the site of Malapa in the Cradle of Mankind World Heritage Site near Johannesburg.
They were then virtually prepared – to avoid the risk of damage – and reunited with fossils recovered during earlier work at the site and fossils found articulated with skeletal spines, part of the original specimens of Australopithecus sediba for the first time. was described in 2010. ,
The discovery also established that sediba, like humans, had only five lumbar vertebrae.
“While Issa was already one of the most complete skeletons of an ancient hominin ever discovered, these vertebrae practically complete the lower part and make Issa’s lumbar region not only the best-preserved hominin lower body ever discovered. but probably also the best preserved,” said Professor Lee Berger, an author on the study and leader of the MALPA project.
Issa’s excellent preservation helped to show that the curvature of Sediba’s spine was more extreme than that of any other Australopithecus yet discovered – that kind of spine curvature is typically seen in modern humans and is strong for bipedalism. Shows customization.
“While lordosis (inward curve of the lumbar spine) and other features of the spine represent clear adaptations to walking on two legs, there are other features, such as large and upward-oriented transverse processes, which suggest powerful trunk musculature. , perhaps to plantation behavior,” said Stony Brook University professor Gabriele Rousseau, another author on the study.
Plantation behavior refers to climbing and living on trees.
“The spine ties it all together,” said study author Professor Thomas Cody Prang of Texas A&M University, who studies how ancient hominins walked and climbed. How these combinations of traits, including possible adaptations to climbing effectively, persisted is perhaps one of the major outstanding questions in human origins.”
The study concluded that Australopithecus sediba was a transitional form of an ancient human relative and that its spine is clearly intermediate in size between modern humans and great apes – meaning that its movements across the species would have both human and ape-like traits.
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