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Possible new human ancestor revealed

April 8, 2010
Courtesy Science
and World Science staff

Two par­tial skele­tons un­earthed in a South Af­ri­can cave are from a pre­vi­ously un­known spe­cies of hom­i­nid, or ex­tinct hu­man­like crea­ture, ac­cord­ing to sci­en­tists. Re­search­ers say the find­ing is shed­ding new light on the ev­o­lu­tion of our own spe­cies, Ho­mo sapi­ens.

The in­ves­ti­ga­tors de­scribed the crea­ture as an up­right walk­er that was also able to climb in trees using ape-like arms. It shared many phys­i­cal traits, they said, with the ear­li­est known spe­cies in the ge­nus Ho­mo, the ev­o­lu­tion­ary line­age to which our own spe­cies be­longs.

A skull reconstruction (in the back­ground) and ori­gi­nal skull of a new spe­cies dubbed Aus­tra­lo­pithe­cus sed­iba. (Cour­tesy U. of Zu­r­ich, Swit­zer­land)
Dubbed Aus­tra­lo­pithe­cus sed­iba, the new­found spe­cies may thus be an an­ces­tor of hu­mans, they added.

Pa­le­oan­thro­po­l­o­gist Lee Berger of the Uni­vers­ity of the Wit­wa­ters­rand in South Af­ri­ca and col­leagues said they un­earthed the bones in cave de­posits at Ma­la­pa, South Af­ri­ca, after Ber­ger’s young son came across them. 

The re­mains in­clud­ed most of a skull, pel­vis, and an­kle. 

The two crea­tures—an adult fe­male and an ado­le­scent male—are 1.95 mil­lion to 1.78 mil­lion years old, and were found close to­geth­er in an ar­ea long pro­tected from sca­vengers, leav­ing the fos­sils well-pre­served, the re­search­ers said.

The in­ves­ti­ga­tors said the an­i­mal al­so shares traits with an­oth­er line­age be­lieved to be re­lat­ed to hu­mans—the ge­nus, or ev­o­lu­tion­ary group, Aus­tra­lo­pithe­cus. There­fore the two skele­tons could rep­re­sent a tran­si­tion­al form be­tween that ge­nus and Ho­mo, the in­ves­ti­ga­tors pro­posed.

The re­search­ers de­scribe the hom­i­nid’s phys­i­cal traits, not­ing un­ique pel­vic fea­tures and small teeth that it shared with early Ho­mo spe­cies. Based on its phy­sique, they sug­gest that the new spe­cies de­scended from Aus­tra­lo­pithe­cus afri­ca­nus, and that the hom­i­nid’s ap­pear­ance sig­ni­fied the dawn of more energy-efficient walk­ing and run­ning. 

The find­ings are re­ported in the April 9 is­sue of the re­search jour­nal Sci­ence.

The re­search­ers al­so iden­ti­fied the fos­sils of at least 25 oth­er spe­cies of an­i­mals in the ca­ve, in­clud­ing saber-toothed cats, a wild­cat, a brown hy­e­na, a wild dog, an­telopes, and a horse. They sug­gest that the Malapa ca­ves were tens of me­ters (yards) deep when the human-like fos­sils were de­posited, and al­so pro­pose that the cave dwell­ing could have acted as a death trap for an­i­mals seek­ing wa­ter. Se­di­ba means “wa­ter well” or “spring” in the lo­cal se­So­tho lan­guage.

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Two partial skeletons unearthed in a South African cave are from a previously unknown species of hominid, or extinct humanlike creature, according to scientists. Researchers say the finding is shedding new light on the evolution of our own species, Homo sapiens. The investigators describe the creature as an upright walker that shared many physical traits with the earliest known species in the genus Homo, the evolutionary lineage to which our own species belongs. Dubbed Australopithecus sediba, the newfound species may thus be an ancestor of humans, they added. Paleoanthropologist Lee Berger of the University of the Witwatersrand South Africa and colleagues reported that they discovered the bones in cave deposits at Malapa, South Africa. The remains included most of a skull, pelvis, and ankle of the new species. The two creatures—an adult female and a juvenile male—are 1.95 million to 1.78 million years old, and were found close together in an area long protected from scavengers, leaving the fossils well-preserved, the researchers said. The investigators said the animal also shares traits with another lineage believed to be related to humans—the genus, or evolutionary group, Australopithecus. Therefore the two skeletons could represent a transitional form between Australopithecus and Homo, the investigators proposed. The researchers describe the hominid’s physical traits, noting unique pelvic features and small teeth that it shared with early Homo species. Based on its physique, they suggest that the new species descended from Australopithecus africanus, and that the hominid’s appearance signified the dawn of more energy-efficient walking and running. The findings are reported in the April 9 issue of the research journal Science. The researchers also identified the fossils of at least 25 other species of animals in the cave, including saber-toothed cats, a wildcat, a brown hyena, a wild dog, antelopes, and a horse. They suggest that the Malapa caves were tens of meters (yards) deep when the human-like fossils were deposited, and also propose that the cave dwelling could have acted as a death trap for animals seeking water.