Associate Professor Darryl J. de Ruiter of the Texas A&M University Department of Anthropology, and Dr. Thomas J. DeWitt of Texas A&M’s Department of Wildlife and Fisheries Sciences are among a team of co-authors from the U.S. and South Africa of a report published in the April 2013 edition of the journal Science.
The paper, “Mandibular Remains Support Taxonomic Validity of Australopithecus sediba,” refers to nearly two million year-old partial skeletal remains of a juvenile hominid, around 9 – 13 years of age and an adult female, which was unearthed in 2008 in a cave at Malapa, about 30 miles north-northwest of Cape Town, South Africa. The partial skeletons were initially described in two papers in Science by their discoverers, paleoanthropologist Lee Berger of the University of the Witwatersrand, South Africa, and colleagues as a previously unknown species of early human ancestor called Australopithecus sediba.
The National Geographic reports that at an April, 2012 international gathering of anthropologists in Minneapolis, Dr. Berger and his colleagues laid out arguments for why the Malapa species, known as Australopithecus sediba, may represent an intermediate form between the primitive australopiths and our genus, Homo.
That assessment was not uncontroversial in the anthropology community, but the authors of the April, 2013 Science report say that examination of the South African remains using a method called morphometrics, which uses math and 3-D models to create replicas of the jawbone, provides “definitive proof” that Australopithecus sediba is a different species unlike anything seen previously.
The report abstract says that while questions have been raised over the announcement of the species Australopithecus sediba as to whether the Malapa fossils represent a valid taxon or whether inadequate allowance was made for intraspecific variation, the morphology of mandibular remains of Au. sediba, including newly recovered material discussed in the report, shows that it is not merely a late-surviving morph of Au. africanus. Rather, say the authors, “as is seen elsewhere in the cranium, dentition, and postcranial skeleton — these mandibular remains share similarities with other australopiths but can be differentiated from the hypodigm of Au. africanus in both size and shape as well as in their ontogenetic growth trajectory.”
Dr. De Ruiter told the Bryan-College Station’s Andrea Salazar that he hesitates to call the Malapa fossil a missing link, preferring the term “transitional form” describing a creature that shares many characteristics with Australopithecines and the genus Homo, noting that “Every part of the skeleton that we looked at, from the head to the jaw to the teeth … to the feet to the hands, everything, shows this mosaic of ancestral characters, plus characters found in its descendants, the genus homo — us, humans,” and that the research will continue for decades, outliving him.