How Au. Sediba walked, chewed and moved

The papers report on some of the most complete early human ancestral remains ever discovered. The 2-million-year-old fossils belong to the species Australopithecus sediba (Au. sediba) and provide what Berger, from the Wits Evolutionary Studies Institute, describes as "unprecedented insight into the anatomy and phylogenetic position of an early human ancestor."

The six papers represent the culmination of more than four years of research into the anatomy of Au. sediba based on the holotype and paratype skeletons commonly referred to as MH1 and MH2, as well as the adult isolated tibia referred to as MH4. The fossil remains were discovered at the site of Malapa in August of 2008, and the species was named in 2010 by Berger and his colleagues. The articles presented in Science complete the initial examination of the prepared material attributed to these three individuals.

The papers are entitled: Dental morphology and the phylogenetic "place" of Australopithecus sediba; Mandibular remains support taxonomic validity of Australopithecus sediba; The upper limb of Australopithecus sediba; Mosaic morphology in the thorax of Australopithecus sediba; The vertebral column of Australopithecus sediba; and The lower limb and the mechanics of walking in Australopithecus sediba, with the introduction entitled The Mosaic Anatomy of Australopithecus sediba.

In essence, the six studies describe how the 2-million-year-old Au. sediba walked, chewed and moved.

Berger summarises that Au. sediba provides us with the most comprehensive examination of the anatomy of a definitive single species of early hominin. "This examination of a large number of associated, often complete and undistorted elements, gives us a glimpse of a hominin species that appears to be mosaic in its anatomy and that presents a suite of functional complexes that are both different from that predicted for other australopiths, as well as that for early Homo.

Such clear insight into the anatomy of an early hominin species will clearly have implications for interpreting the evolutionary processes that affected the mode and tempo of hominin evolution and the interpretation of the anatomy of less well preserved species," says Berger.

"Aside from the 26 authors from 16 institutions involved in these publications, the team focusing its research efforts on Au. sediba and Malapa now numbers more than 100 researchers from around the world and represents one of the largest dedicated archaeological or palaeontological research programmes," says Prof. Loyiso Nongxa, Vice-Chancellor and Principal of the University of the Witwatersrand. Berger adds that the work undertaken to date, although only five years in the making (since the discovery of the site in mid-2008), represents some of the most extensive focused literature on a single early hominin species yet created.

Included in the recent discoveries from the site are a new species of fox, named by the team as Vulpes skinneri just three months ago, and the discovery of more than 300 early human ancestor remains, including parts of skeletons still encased in rock.

Berger concludes: "Discoveries such as Australopithecus sediba and the Malapa site demonstrate the need for further African based exploration in the rich fossil fields of southern Africa, and additionally demonstrate the tremendous promise of the palaeosciences on the continent."