In 2010, a new candidate was announced for humanity’s evolutionary tree—Australopithecus sediba.1 Now, recent analyses of its fossilized bones are being reported as further proof of its ancestral standing.
However, headlines presenting it as another rung on the human evolutionary ladder—such as “2-million-year-old fossils raise hope over ‘missing link,'”2 “Fossil Trove Sheds Light On a Stage of Evolution,”3 and “Rethinking Human Origins: Fossils Reveal a New Ancestor on the Family Tree”4—all fly in the face of the actual data found in the five detailed reports describing it in the journal Science.
One of the scientific reports examined the features of each bone in the wrist and hand from what appears to have been an adult female. The unique hand doesn’t look like a modern ape’s, a modern human’s, or even some sort of gradual transition between the two. The researchers described it as a “mosaic” of features.5
“Sediba’s” finger bones were long, curved, and—”together with its primitive australopith-like upper limb”—demonstrate that this small primate was fit for swinging through trees, unlike ground-dwelling humans.5
Also, Sediba’s thumb was long and skinny. The human thumb is shorter in proportion to the fingers so that it can be used to build things and handle “large loads during stone tool production.” So Sediba’s thumb probably “was not subject to the same type or frequency of loading as that of other contemporary or later hominins.”5 Thus, this creature’s anatomy shows strong evidence that it did swing from tree branches and, despite reports to the contrary, did not make tools.
The study authors wrote that the uniqueness of Sediba’s hand “adds to the range of morphological [shape] variation previously documented in the hominin carpometacarpal [wrist] joints and to the ambiguity surrounding the polarity and functional significance of some of these features.”5
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