Australopithecus sediba ‘walked like a human, but climbed like an ape’

The discovery of two-million-year-old fossil vertebrae from Australopithecus sediba, an ancient human relative, shows that early hominins walked like humans but climbed like apes.

Scientists say the new lower back fossils are the “missing link” that settles a decades-old debate – hominins used their upper limbs to climb like apes and their lower limbs to walk like humans.

An international team of scientists from New York University, the University of the Witwatersrand and 15 other institutions announced their findings on Wednesday in the open-access journal e-Life.

The lower back fossils are two million years old and were discovered in 2015, in Malapa, in the Cradle of Humankind World Heritage Site, just northwest of Johannesburg.

Malapa is the site where, in 2008, University of the Witwatersrand’s Professor Lee Berger and his then nine-year-old son, Matthew, discovered the first remains of our ancient human relative named Australopithecus sediba.

The recovery of new lumbar vertebrae from the lower back of Australopithecus sediba and portions of other vertebrae of the same female, together with previously discovered vertebrae, form one of the most complete lower backs ever found.

It provides insight into the way early hominins walked and climbed.

“The lumbar region is critical to understanding the nature of bipedalism in our earliest ancestors, and to understanding how well adapted they were to walking on two legs,” said New York University and Wits University and lead author on the paper, Professor Scott Williams.

Previous studies of early hominins have highlighted its transitional nature between walking like a human and climbing adaptations. Other features that were studied include the upper limbs, pelvis and lower limbs.

“The spine ties this all together,” says Professor Cody Prang of Texas A&M. Prang studies how ancient hominins walked and climbed.

“In what manner these combinations of traits persisted in our ancient ancestors, including potential adaptations to both walking on the ground on two legs and climbing trees effectively, is perhaps one of the major outstanding questions in human origins.”

The study concluded that sediba is a transitional form of an ancient human relative, and its spine is intermediate in shape between modern humans, Neandertals and great apes.

Compiled by Narissa Subramoney

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