The discovery of new Australopithecus sediba fossils mean we can now reconstruct most of the spine of one individual, and strengthen the case that the species was bipedal at least some of the time
23 November 2021
Spinal bones of an extinct human relative have been found in lumps of rock blasted out of a South African cave and used to reconstruct one of the most complete back fossils of any hominin.
The spine was curved, suggesting that Australopithecus sediba spent a lot of time walking on two legs.
A. sediba was first described in 2010 by Lee Berger at the University of the Witwatersrand in Johannesburg, South Africa, and his team. They described two partially preserved individuals: a male child called Karabo and an adult female. Both were found in the Malapa cave system and lived about 2 million years ago.
Malapa was first excavated by miners around a century ago, and some of the first A. sediba bones were found in chunks of rock that had been blasted from the cave with dynamite.
The miners used some of the blocks to build a road. For the past decade, Berger’s colleagues have been chipping away at these blocks. One has now yielded four vertebrae from the lower back of the female, plus a bone called the sacrum that links the spine to the pelvis. The team has named the female Issa, which means “protector” in Swahili.
The new bones mean that most of Issa’s lower back has now been excavated. After fitting the vertebrae together, the team concluded that her spine was curved so that, when viewed from the side, it forms a gentle S-shape, a characteristic of humans that keeps the body’s mass centred over the pelvis for efficient bipedal walking.
However, previous studies of A. sediba had also found clear adaptations in the upper body for tree climbing, suggesting it was halfway between tree-dwelling apes and fully bipedal humans.
The new analysis backs this up, says Scott Williams at New York University. “It’s reinforcing what has been said before,” he says.
Journal reference: eLife, DOI: 10.7554/eLife.70447
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