[News] Fossil links human species

[Michaelangelica]

A team led by Professor Lee Berger of the University of Witwatersrand in South Africa and Professor Paul Dirks now at James Cook University have discovered a new species of hominid believed to be “a good candidate for being the transitional species” between humans and ape-man.

 

Named Australopithecus sediba the fossils were discovered by Wits University scientists in the Cradle of Humankind World Heritage Site and are owned by the people of South Africa.

 

Two partial skeletons – a juvenile male and an adult female – were found in a cave by Professor Berger about 40km north west of Johannesburg. In fact it was Professor Berger’s nine-year-old son Matthew who found the first remains – a collar bone.

 

The hominid fossils are arguably the most complete skeletons of early hominids ever discovered and are by far the most complete remains of any hominid dating to around two million years ago.

 

Two papers relating to the discovery are being published today (April 9) in the journal Science. Professor Berger is lead author on the first paper and Professor Dirks lead author on the second.

 

The unique find was made after Professors Dirks and Berger embarked on a study on the geological controls of cave distribution and formation in the Cradle of Humankind.

 

An international team of more than 60 scientists have since been involved in the project including Dr Robyn Pickering of the University of Melbourne and Dr Andrew Herries from the University of New South Wales. Both were involving in dating either the rocks or debris encasing the fossils and are co-authors on the paper with Professor Dirks.

 

The new species has been named sediba which means natural spring, fountain or wellspring in Sotho, one of the 11 official languages of South Africa.

 

“Sediba was deemed an appropriate name for a species that might be the point from which the genus Homo arises,” Professor Berger said.

 

Prof Berger with skeleton of male child

 

“I believe that this is a good candidate for being the transitional species between the south African ape-man Australopithecus africanus - like Taung Child and Mrs Ples- and either Homo habilis or even a direct ancestor of Homo erectus – like Turkana Boy, Java man or Peking man,” he said.

 

The team have compared the skeletons with all the remains of fossil hominds that have been discovered and in many ways they are absolutely unique from any fossil species found.

 

The sediba species has long arms, like an ape, short powerful hands, a very advanced pelvis (hip bone) and long legs capable of striding and possibly running like a human. It is likely that they could have climbed.

 

“It is estimated that they were both about 1.27 metres tall, although the child would certainly have grown taller. The female probably weighed about 33 kilograms and the child about 27 kilograms at the time of his death,” Professor Berger said.

 

“The brain size of the juvenile was between 420 and 450 cubic centimetres, which is small (when compared to the human brain of about 1200 to 1600 cubic centimetres) but the shape of the brain seems to be more advanced than that of Australopithecines.

 

“Our study indicates that Australopithecus sediba could be a better ancestor of Homo erectus than Homo habilis and it may certainly help to clear up some of this ‘muddle in the middle’,” Professor Berger said.

 

Professor Dirks said that through a combination of faunal, U-Pb and palaeomagnetic dating techniques, the age of the rocks encasing the fossils had been determined at 1.95-1.78 million years ago. Cosmogenic dating was used to interpret the landscape formation and to determine the depth of the cave at the time.

 

“Dating involved a double blind U-Pb date, conducted independently by Jan Kramers of the University of Bern in Switzerland and by Dr Pickering of the University of Melbourne, which is a first in the dating of flowstone deposits in the Cradle of Humankind,” he said.

 

“Once an absolute date had been obtained, paleomagnetic analysis by Dr Herries of the University of New South Wales was used to constrain the age of the debris flow encasing the fossils. These ages coincide with the period in which the species of the genus Australopithecus are gradually being replaced by species of the genus Homo, of which we, Homo sapiens are part.”

 

Professor Dirks said that the geological studies demonstrated the dynamic nature of the landscape in which sediba lived and died, and that the current landscape in the Cradle was significantly different from that of two million years ago.

 

The skeletons, which were first discovered in August 2008, were found amongst the articulated skeletons of a sabre-toothed cat, antelope, mice and rabbits. They are preserved in a hard, concrete like substance known as calcified clastic sediment that formed at the bottom of what appears to be a shallow underground lake or pool that was possibly about 50 metres tall about 1.9 million years ago.

 

Fossil preparators have worked arduously over the past two years to extract the bones from the rock. The site continues to be explored and without a doubt there are more groundbreaking discoveries to come forth.

 

Professor Berger, a paleaoanthropologist, is Senior Research Officer and Director of the Institute of Human Evolution in School of GeoSciences at the University of Witwatersrand in South Africa.

 

Professor Dirks, a structural geologist, is head of the School of Earth and Environmental Sciences at James Cook University in Australia and was Head of the School of Geosciences, University of Witwatersrand in Johannesburg, South Africa, from 2002 until 2009.

 

Contacts:

 

James Cook University: Jim O’Brien (07) 4781 4822, 0418 892 449

 

University of Melbourne: Rebecca Scott 0417 164 791

 

University of New South Wales: Steve Offner (02) 9385 8107 or 0424 580 208

 

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Issued: April 9 2010 :shrug: