elifesciences.org
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Illustration of Australopithecus sediba.
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Nationalgeographic.co.id—An international group of scientists from New York University, the University of the Witwatersrand and 15 other institutions announced a discovery that was the “missing link” that settled decades of debate. This discovery proves that early hominins used their upper limbs to climb like apes, and their lower limbs to walk like humans.
The scientists have published reports of their findings in an open access journal eLife. They reported finding a two-million-year-old fossilized spine of an extinct species of ancient human relative.
They named this new hominin species as Australopithecus sediba. For researchers, the fossils of this species have provided insight into how these early human relatives walked and climbed.
This lower back fossil was discovered in 2015 during excavations of a mining track that runs next to the Malapa site at the Cradle of Humankind World Heritage Site, northwest of Johannesburg, South Africa.
Malapa is the site where Professor Lee Berger of the University of the Witwatersrand and his then nine-year-old son, Matthew, discovered the first remains of a new species of ancient human relative named Australopithecus sediba that. They found it in 2008.
They then carried out excavations in the following years and found other bone parts of the species. The fossils of this species were later found to be about two million years old.
The spine of this species is found in consolidated cement-like rocks, known as breccias. The discovery of the fossil of this new species is one of only two early hominin skeletons that still have relatively complete vertebrae and lower teeth, thus providing certainty as to which species possessed these vertebrae.
Initially the researchers referred to the species that owned the fossil as female “Issa” to facilitate identification and naming of the fossils. In the local Swahili language, the name Issa means protector
“While Issa is already one of the most complete skeletons of an ancient hominin ever found, this spine practically completes his lower back and makes Issa’s lower back (lumbar spine) area not only the best hominin lower back ever discovered, but also possibly the best. preserved,” said Berger, who is the author of the report on the findings and the lead of the Malapa project Heritage Daily.
Berger also added that this combination of completeness and preservation of the fossils gave the team an unprecedented look at the anatomy of the species’ lower back.
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Previous studies of the lower spine of this species hypothesized that sediba had only a relatively straight spine, without the curvature, or lordosis, typically seen in modern humans. They further hypothesized that Issa’s spine is more similar to that of extinct Neanderthal species and other, more primitive hominin species that are more than two million years old.
Lordosis is a curve in the spinal cord and is commonly used to indicate a strong adaptation to bipedalism. Bipedalism is a form of terrestrial movement in which an organism moves using two legs.
However, with the more complete vertebrae found, and the excellent preservation of the fossils, this study found that lordosis sediba was actually more extreme than any other australopithecus ever found.
“While the presence of lordosis and other features of the spine represent a clear adaptation to walking on two legs, there are also other features, such as a large, upward-oriented transverse process, which suggests strong trunk muscles, possibly for arboreal behavior. ,” said Professor Gabrielle Russo of Stony Brook University who co-authored the study report on the new findings.
Strong, upward-pointing vertebrae usually indicate strong body muscles, as observed in apes. Professor Shahed Nalla of the University of Johannesburg and Wits who is a rib expert and researcher on the study said: “When combined with other parts of the torso anatomy, this suggests that the sediba retains a distinct adaptation to climbing.”
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Previous studies of this ancient species have highlighted mixed adaptations across the skeleton in sediba that have shown transitional traits between human-like walking and climbing adaptations. This includes the features studied in the upper limbs, pelvis, and lower limbs.
“The spine holds all of this together,” said Professor Cody Prang of Texas A&M, who studies how early hominins walked and climbed.
“In what ways these combinations of traits persisted in our ancestors, including potential adaptations for walking on the ground on two legs and climbing trees effectively, is perhaps one of the most outstandingly large questions about human origins.”
The study concluded that the sediba was a transitional form of an early human relative and that the backbone was clearly intermediate between modern humans (and Neanderthals) and great apes.
“Issa walks like a human but can climb like an ape,” concluded Berger.
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