January 24, 2022 1:22 pm

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

Daniel Garcia Martinez, of the Anthropology Unit of the Complutense University of Madrid (UCM) and affiliate member of the National Center for Research on Human Evolution (PRICEH) is part of the international team of scientists that has just published in the journal e-Life the discovery of fossil vertebrae two million years old of an extinct species, Australopithecus sediba.

These vertebrae resolve a decades-long debate by showing that the first hominids they used their upper limbs to climb like apes and their lower limbs to walk like humans.

The recovery in a rock of new vertebrae of the spinal column of a single individual from Australopithecus sediba, found in 2015 at the Malapa site (Johannesburg, South Africa), together with the vertebrae discovered in 2008, form one of the most complete lumbar columns in the fossil record and they give an idea of ​​how this ancient human relative walked and climbed.

The first hominids used the upper extremities to climb like apes and the lower ones to walk like humans

The discovery also establishes that, like humans, sediba had only five lumbar vertebrae. “The lumbar region is essential to understand the nature of the bipedalismo in our first ancestors and to understand how well adapted they were to walk on two legs ”, he explains Scott Williams, lead author of the study.

One of the most complete skeletons

The fossils were virtually reconstructed, after being scanned by computed microtomography –Method of X-ray analysis where the internal and external image of an object is represented in 3D–, thus eliminating the risk of damaging the delicate bones.

Once virtually reconstructed, the vertebrae were added to previously recovered fossils, which perfectly articulated with the vertebral column of the fossil skeleton MH 2, part of the original type specimens of Australopithecus sediba described for the first time in 2010.

The female skeleton MH 2, dubbed by researchers as Issa (‘protector’ in Swahili), is one of the first two hominin skeletons to retain both a relatively complete lower spine and the dentition of the same individual, which allows to be certain about the species to which the vertebral column belongs.

Issa is one of the first two hominid skeletons to retain both a relatively complete lower spine and the dentition of the same individual.

“While Issa was already one of the most complete skeletons of an ancient hominin ever discovered, now these vertebrae complete his lower back and make his lumbar region a competitor, not only for the most complete hominin, but also probably the best preserved. This combination of integrity and preservation gave the team an unprecedented look at the lower back anatomy of the species, “he says. Lee Berger, co-author of the study and leader of the Malapa project.

Transitional hominid

According to this work, lordosis of Australopithecus sediba –Excessive curvature of the lower back– is more extreme than that of any other australopithecine discovered so far, only surpassed by that observed in the spine of the Turkana child (Standing man) in Kenya, 1.6 million years old, and from some modern humans.

Regarding the integration of the lumbar spine with other regions of the skeleton, García Martínez indicates that “the ability to use the arboreal environment for locomotion is also observed in some other anatomical regions, such as its narrow upper thorax” .

Sediba is a transitional form of an ancient human relative and its spine is clearly intermediate in shape between modern humans (and Neanderthals) and great apes.

Lee Berger, study author

“These results of sediba fit very well in our other torso reconstructions of transition hominins, where we also see mosaic evolution in other related anatomical systems ”, points out Markus Bastir, from the National Museum of Natural Sciences (MNCN).

Previous studies on the upper extremities, pelvis and lower extremities of this ancient species already noted mixed adaptations through the skeleton in sediba indicating its transitional nature between walking like a human and climbing like an ape.

Sediba it is a transitional form of an ancient human relative and its spine is clearly intermediate in shape between modern humans (and Neanderthals) and great apes. Issa walked like a human, but he could climb like a monkey ”, concludes Berger, who in 2008, together with his nine-year-old son, Matthew, discovered the first remains of what would become this new species.

Reference:

Williams et al. “New fossils of Australopithecus sediba reveal a nearly complete lower back”. eLife.

Rights: Creative Commons.

Reference-www.agenciasinc.es

Comments (0)

Leave a Reply

Your email address will not be published. Required fields are marked *