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67-million-year-old adult female sports the oldest and most complete set of shoulder blades and collarbones of any ancient hominid.
Those fossils also provide the best available model for what the shoulders of the <span class="nlp-<span class="nlp-common“>common“>last common ancestor of humans and chimpanzees looked like, say Kristian Carlson, a paleoanthropologist at the University of Southern California in Los Angeles, and his colleagues.
Their results provide new insights into how both Little Foot and a human-chimp last common ancestor climbed in trees.
Little Foot lived roughly half-way between modern times and the estimated age of a human-chimp common ancestor, says paleobiologist David Green of Campbell University in Buies Creek, N.
If that ancient ancestral creature was about the size of a chimp, as many researchers suspect, shoulders resembling those of gorillas would have supported slow but competent climbing, Green says.
“The maintenance of a gorilla-like shoulder in Little Foot offers clues that climbing remained vital for early ,” Green says.
Researchers used a digital reconstruction of Little Foot’s nearly complete right shoulder blade, shown here, to determine that this ancient hominid climbed more like gorillas than like chimps, orangutans or humans.
The new analysis makes Little Foot’s shoulders “our best candidate for hypothesizing the appearance of the human-chimp last common ancestor,” says anatomist Susan Larson of Stony Brook University School of Medicine in New York, who wasn’t involved in the research.
In the new study, a digital, 3-D reconstruction of Little Foot’s more complete right shoulder blade was compared with right shoulder blades of chimps, gorillas, orangutans and present-day people.
Little Foot’s collarbones were compared with those of humans, chimps, gorillas, orangutans and seven ancient hominids.
Carlson’s analysis provides preliminary but still uncertain evidence that Little Foot had the most gorilla-like shoulders of any ancient hominid, says paleoanthropologist Stephanie Melillo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
Melillo, who did not participate in the new study, considers it most striking that Little Foot shares many shoulder similarities with the other Australopithecus fossils studied by Carlson’s team.
4-million-year-old Ardipithecus ramidus skeleton, dubbed Ardi, the best hominid model for a human-chimp last common ancestor (SN: 12/31/09).