The fossilized shoulder joint of an early hominid named “Little Foot” suggests that the upright species was also competent in swinging trees, with a skill extinct among modern humans.
About 3.7 million years ago in present-day South Africa, a human relative was straddling two evolutionary moments: our propensity to spend time in the trees and our emerging preference for walking on land. That specimen, called StW 573 or Little Foot, was a Australopithecus prometheus. The fossil was completely excavated in 2018, more than 20 years after its discovery, when paleontologists finished extracting the fossil from the breach where it was trapped. Immediately, Little Foot offered a remarkable insight into human origins.
The research describing the morphology of the shoulder joint was published this week in the Journal of Human Evolution. The research team inspected Little Foot’s pectoral girdle – literally, the shoulder blade and neck bone of the specimen. By comparing the formation of the band with that of other human relatives, including some of the great apes, the team analyzed how Little Foot and other people of its species moved.
“By understanding how the shoulder joints of early hominins are structured and, more broadly, how their shoulder blades are able to move over the torso, we can understand how they used their upper limbs while interacting with the environment,” he said. say Kristian Carlson, anthropologist at the University of Southern California and lead author of the new article, in an email. “This is a crucial question during this period of our evolutionary history.”
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In its subtle form, Little Foot’s pectoral girdle indicated to researchers that the hominid exploited trees for survival, perhaps to acquire food or to prevent its transformation. This aligns with research last year at the vertebrae of the specimen, which suggested that Little Foot was capable of making head movements (useful for climbing) that go beyond modern human capabilities. That said, Little Foot was still bipedal, with vertical gait associated with humans. The new finding provides an interesting comparison with Ardi (a copy of Ardipithecus ramidus), a lesser-known old relative 4.4 million years ago. Paleoanthropologists recently suggested that Ardi’s hands were built to swing in the trees, although some experts disagreed, saying Ardi was more human than ape. Although the fossil record is as ossified as it can be, the conclusions drawn from the bones we draw from the ground remain volatile. It will take some time if interpretations of Little Foot’s lifestyle, drawn from these shoulder bones, adhere.
The pectoral girdle of Little Foot is the first proof of this skeletal structure so close to when the hominins separated from the ancestors of apes and bonobos. This upper limb is a crucial piece of the puzzle, although Carlson said it can only tell us a lot.
“As special as Little Foot is, he’s just an individual,” he explained. “While we are still intensively investigating other anatomical regions of the Little Foot skeleton, we must also continue to appreciate the growing morphological variability that appears to exist within the fossil record of early hominins, for example in Australopithecus.”
Based on their comparisons, Carlson’s team determined that the structure of Little Foot’s shoulder may be a good indicator of the appearance of this structure in even larger human relatives, in the time period. from 7 to 8 million years. This discovery would make Little Foot look like a spring chicken. But until that happens, we seem to be stuck with one of the most complete australopithecine fossils ever found, the ongoing analysis of which reveals new details and theories at every step. Woe to us!
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