Australopithecus sediba silhouette showing the newly-found vertebrae along with other skeletal remains from the species. The enlarged detail shows the newly discovered fossils, in colour, between previously known elements in grey.Credit: New York University/Wits University
Fossils recently found in South Africa have proved that early hominids used their upper limbs to climb like apes, and their lower limbs to walk like humans.
A study published in e-Life, by scientists from Wits University, New York University, and other institutions, describes the finding of lumbar vertebrae from the lower back of a single individual. They combined the newly discovered portions with vertebrae of the same female, previously documented, to give insight into how this ancient relative walked and climbed.
The first remains of Australopithecus sediba were discovered in 2008 at the Malapa site in the Cradle of Humankind World Heritage Site, just northwest of Johannesburg. More fossils were discovered in 2015 during excavations of a mining track running next to the site.
Fossils from the site have been dated to approximately two million years ago. The vertebrae described in the present study were recovered in a consolidated cement-like rock, known as breccia. The fossils were prepared virtually after micro-scanning at the University of the Witwatersrand, removing the risk of damaging the closely positioned, delicate bones during manual preparation.
Once virtually prepared, the vertebrae were reunited with fossils from earlier work and found to articulate perfectly with the spine of the fossil skeleton, part of the original Type specimens of Australopithecus sediba first described in 2010.
The female skeleton has been nicknamed ‘Issa,’ meaning protector in Swahili. The discovery also established that like humans, Au. sediba had only five lumbar vertebrae. Issa shows inward of the lumbar spine (lordosis) which is typically used to demonstrate strong adaptations to walking on two legs.
“These vertebrae practically complete the lower back and make Issa’s lumbar region a contender for not only the best-preserved hominin lower back ever discovered, but also probably the best preserved,” says Lee Berger, the Malapa project leader, and Director of the Centre for Exploration of the Deep Human Journey at Wits University of the Witwatersrand. He adds that the preservation gave the team an unprecedented look at the anatomy of the lower back of the species.
The study concludes that Au. sediba is a transitional form of ancient human relative and its spine is clearly intermediate in shape between those of modern humans, Neanderthals and great apes. “Issa walked somewhat like a human but could climb like an ape,” says Berger.
