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Ancient human-like creature's skull probed

12 April 10 18:40 GMT
By Jonathan Amos
Science correspondent, BBC News

X-rays show in stunning detail the interior of the skull of a new human-like creature found in South Africa.

The hominid Australopithecus sediba was presented to the world last week.

The X-ray images reveal information about the ancient animal's brain and tantalising evidence of the insects that may have fed on the dead body.

Its discoverers say it fills a key gap between older creatures and the group of more modern species known as Homo, which includes our own kind.

The work was conducted at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, which has developed expertise in the non-destructive study of fossils.

Probing such artefacts with a brilliant light source is the only way to see inside the specimens without actually breaking them apart.

South African researchers took the skull of the juvenile, 1.9-million-year-old creature, and many other parts of its skeleton, to the European facility for a two-week investigation.

Firm age

The ESRF uses a technique known as micro-tomography to assemble its images. This involves taking a series of a high-contrast, high-resolution X-ray radiographs of the target fossil in rotation to build up a 3D representation.

One of the main reasons for undertaking the study was so that scientists could learn more about A. sediba's teeth and get a firm age for the juvenile at death.

The X-ray images can discern the fine details of internal growth lines and other hidden features.

"The teeth are very beautiful especially the third molars, the non-erupted teeth; and given the quality of the scans we will have no problem virtually extracting them to study them," said the ESRF's Dr Paul Tafforeau.

"What we want to know is the real age at death and not just the developmental age, or modern-equivalent age, because what we want to track is how, during the evolution of hominids, the life stories slowed down - to go from a pattern that is rapid like apes to one which is slow like modern humans," he told BBC News.

It will take a year at least to complete this investigation.

The analysis of the terabytes of data produced at the ESRF has only really just started, but the early analysis of the complete skull has already thrown up some intriguing observations.

Among them are what appear to be three fossilised insect eggs inside the skull.

Cautious approach

"We have to be cautious because it is possible they are modern insects; we have to look more at the data," said Dr Tafforeau.

"But their high density suggests they are fossils, and if that is the case they could correspondent to the insects that came to eat on the flesh of the body at the time of death."

Researchers also identified a low-density area within the skull which could be a remnant of the brain after its bacterial decay. The scientists liken it to a natural cast, perhaps made of clays that filled the brain cavity after decomposition.

It is highly unusual for important fossils like A. sediba to be taken out of their country of discovery. The one major exception is for detailed scientific investigation using techniques that are only available abroad; and South Africa has no synchrotron facility.

Since its first presentation last week, A. sediba has generated some controversy in palaeoanthropology circles, with many competing scientists arguing over the true status and position of the creature in the human family tree.

What is not in doubt, however, is the quality and beauty of the latest fossil finds.

The remains of an adult female were found alongside those of the juvenile hominid investigated at the ESRF.

The fossils had been laid down in cave deposits at Malapa in the famous Cradle of Humankind World Heritage Site close to Johannesburg.

The ongoing investigation of the site is being led by Professor Lee Berger of the University of the Witwatersrand.

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