"Long before it's in the papers"
September 09, 2011

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Oldest known human ancestor may be about 2 million years old

Sept. 9, 2011
Courtesy of the University of Melbourne
and World Science staff

Re­search­ers have dat­ed as 1.98 mil­lion years old a fos­sil that rep­re­sents a can­di­date for old­est known di­rect hu­man an­ces­tor.

Scientists reached the result after con­ducting new dat­ing studies of the early hu­man fos­sils found in South Af­ri­ca last year, dubbed Aus­tra­lo­pith­e­cus sed­iba.

A skull reconstruction (in the back­ground) and ori­gi­nal skull of a new spe­cies dubbed Aus­tra­lo­pithe­cus sed­iba. (Cour­tesy U. of Zu­r­ich, Swit­zer­land)
Stud­ies on newly ex­posed cave sed­i­ments at the Malapa Cave site in South Af­ri­ca, where the fos­sils were found, has helped re­search­ers est­i­mate their age more pre­cise­ly, they say, mak­ing the Malapa site one of the best dat­ed early hu­man sites in the world.

A group of pa­pers pub­lished Sept. 8 in a spe­cial is­sue of the jour­nal Sci­ence pre­s­ent the find­ings, as well as more de­tailed stud­ies of the hands, feet, pel­vis and brain. The date es­ti­mates, us­ing tech­niques known as ura­ni­um lead dat­ing and palaeo­mag­netic anal­y­sis, were car­ried out by the Uni­vers­ity of Mel­bourne and La Trobe Uni­vers­ity in Aus­tral­ia.

The re­search­ers said they pinned down the age of the fos­sils to with­in 3000 years.

“Know­ing the age of the fos­sils is crit­i­cal to plac­ing them in our family tree, and this new age means that Aus­tra­lo­pith­e­cus sed­iba is the cur­rent best can­di­date for our most dis­tant hu­man an­ces­tor,” said Rob­yn Pick­er­ing of the Uni­vers­ity of Mel­bourne, a lead re­search­er in­volved in the dat­ing of the flow­stone sur­round­ing the fos­sils

“The re­sults of these stud­ies pre­s­ent ar­guably the most pre­cise dates ev­er achieved for any early hu­man fos­sils,” she added. The fos­sils seem to have been de­posited in the Malapa Cave dur­ing a 3,000-year pe­ri­od when the Earth’s mag­net­ic field rev­ersed it­self by 180 de­grees and back again, mem­bers of the team said.

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Researchers have dated as 1.98 million years old a fossil that represents a candidate for our oldest known direct human ancestor. The discovery was made after researchers conducted further dating of the early human fossils, dubbed Australopithecus sediba, found in South Africa last year. Studies on newly exposed cave sediments at the Malapa Cave site in South Africa, where the fossils were found, has helped researchers determine their age more precisely, making the Malapa site one of the best dated early human sites in the world, the scientists say. A group of papers published Sept. 8 in a special issue of the journal Science present the findings, as well as more detailed studies of the hands, feet, pelvis and brain. The date estimates, using techniques known as uranium lead dating and palaeomagnetic analysis, were carried out by the University of Melbourne and La Trobe University in Australia. The researchers said they pinned down the age of the fossils to within 3000 years. “Knowing the age of the fossils is critical to placing them in our family tree, and this new age means that Australopithecus sediba is the current best candidate for our most distant human ancestor,” said Robyn Pickering of the University of Melbourne, a lead researcher involved in the dating of the flowstone surrounding the fossils “The results of these studies present arguably the most precise dates ever achieved for any early human fossils,” she added. The fossils seem to have been deposited in the Malapa Cave during a 3,000-year period when the Earth’s magnetic field reversed itself by 180 degrees and back again, members of the team said.