Fossils suggest that ancestors walked like humans and climbed like apes.

An ancient human relative was able to walk on the ground on two legs and use his upper limbs to climb and swing like apes., according to a new study of fossil vertebrae 2 million years old.

An international team of scientists from New York University, the University of the Witwatersrand and 15 other institutions studied lumbar bones found in 2015 that belonged to a woman. Australopithecus sediba, a type of ancient hominid.

Along with previously discovered bones from the same individual – nicknamed “Issa”, meaning protector in Swahili – the fossilized remains form one of the most complete backbones ever discovered in early hominin records, and give an indication of how this human relative would have changed. around the world.

The researchers said the recently studied lumbar fossils were a missing link that proved that early hominids 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 for a mining trail alongside Malapa, a World Heritage Site Cradle of Humanity, near Johannesburg.

So, they were virtually prepared, to avoid the risk of damage, and rejoined with other fossils previously found – which fit with the spine of the fossil skeleton. They are part of the original Australopithecus sediba specimens first reported in 2010.

The discovery also established that, like humans, the sediba it had only five lumbar vertebrae.

Issa’s excellent preservation helped show that the curvature of the spine of the sediba was more extreme than any other Australopithecus already discovered – this type of spinal curvature is typically seen in modern humans and demonstrates strong adaptations to bipedalism.

“Although the presence of lordosis (the inner curve of the lumbar spine) and other characteristics of the spine represent clear adaptations to walking on two legs, there are other characteristics, such as large, upward-oriented transverse processes, which suggest a powerful musculature of the trunk, perhaps for arboreal behaviors,” said Professor Gabrielle Russo, from Stony Brook University, another author of the study.

Arboreal behaviors refer to climbing and living in trees.

“The spine ties it all together,” added study author Professor Thomas Cody Prang of Texas A&M University, who studies how ancient hominids walked and climbed. “How these combinations of traits persisted in our ancestors, including possible adaptations to both walking on two legs and climbing trees effectively, is perhaps one of the main outstanding questions in human origins.”

The study concluded that the Australopithecus sediba it was a transitional form of an ancient human relative, and its spine is clearly intermediate in form between those of modern humans and the great apes – meaning that the species would have possessed both human and ape traits in its movements.

The study was published Tuesday (23) in the journal e-Life.

Translated text. Read the original in English.