Human brain evolution, new insight through X-rays

Sep 08, 2011
This is a 3-D rendering of the skull of Australopithecus sediba made from X-ray data gathered an experiment at the ESRF beamline ID19. Credit: ESRF/P. Tafforeau

A paper published today in Science reveals the highest resolution and most accurate X-ray scan ever made of the brain case of an early human ancestor. The insight derived from this data is like a powerful beacon on the hazy landscape of brain evolution across the transition from Australopithecus to Homo.

The publication is part of a series of five papers based on new evidence pertaining to various aspects of the anatomy of the species Australopithecus sediba (announced in April 2010 by Berger et al.) published in Science on 9 September 2011. Led by the University of the Witwatersrand in Johannesburg (South Africa), over 80 scientists from numerous institutes in Germany, the U.S., UK, Australia, Germany South Africa and Switzerland worked on the project. The work on the includes a scientist from the European Synchrotron Radiation Facility (ESRF) in Grenoble (France), where the X-ray micro-tomography scan was performed.

The exceptionally well-preserved cranium of MH 1 (Australopithecus sediba) was scanned at the ESRF at a resolution (3-D pixel size) of around 45 microns, just below the size of a human hair. Thanks to this high resolution, incredible details of the anatomy of sediba's endocast could be revealed.

According to Prof. Lee Berger from the University of the Witwatersrand in Johannesburg (South Africa) who found the fossil in 2009, "the many very advanced features found in the brain and body make it possibly the best candidate ancestor for our genus, the genus Homo, more so than previous discoveries such as Homo habilis."

This image shows a comparison of a classical computer tomography (CT) scan (left) with a scan using synchrotron microtomography at the ESRF (right). The much higher resolution and contrast are clearly visible. The lower part depicts a zoom-in view of an area which on the upper part is indicated with a square. This area includes a tooth and a cavity in the skull. Credit: ESRF/P. Tafforeau

Humans have a very large brain relative to their body size, about four times that of . Evolution from the brain of our shared ancestor with chimpanzees has seen this radical size increase. However, the reconstructed endocast (volume of the cranium) of MH1 is surprisingly small, with a volume of 420 cm3, on average only about 40 cm3 larger than chimpanzees.

The study of this brain shows a surprising mix of characteristics. Its overall shape resembles humans more than chimpanzees and, given its small volume, this result is consistent with a model of gradual neural (brain) reorganisation in the front part of the brain. "Indeed, one of our major discoveries is that the shape and form of sediba's brain is not consistent with a model of gradual brain enlargement, which has been hypothesised previously for the transition from to Homo", adds Dr Kristian Carlson from the University of the Witwatersrand, who is the main author of the paper.

This image shows a reconstruction of the skull of MH1 (partially transparent) with the brain endocast depicted in green. Dentition also visible and the specimen is viewed from slightly above and anterolateral. Credit: Witwatersrand University/K. Carlson

Use of synchrotron X-rays was instrumental for this discovery. The external shape of a brain is reflected, like in a mould, in the inner surface of a cranium. By mapping the contours of this internal surface, an image of the original brain located in the skull can therefore be produced. However, the skull of MH-1 was not emptied from bedrock after its discovery, and only the powerful X-rays at the ESRF could penetrate deep into the fossil to reveal the cranium's interior shape at the desired resolution. Leaving the rock inside the cranium also ensured that its delicate inner surface was not damaged or altered during its extraction.

"The ESRF is the most powerful installation worldwide for scanning fossils, setting the standard for what can be achieved during non-destructive studies of internal structures of fossils," concludes Paul Tafforeau, staff scientists at the ESRF and a co-author of the paper.

Explore further: Egypt archaeologists find ancient writer's tomb

More information: The Endocast of MH 1, Australopithecus sediba, Kristian J. Carlson, Dietrich Stout, Tea Jashashvili, Darryl J. de Ruiter, Paul Tafforeau, Keely Carlson, Lee R. Berger, SCIENCE 9 September 2011

Provided by European Synchrotron Radiation Facility

5 /5 (3 votes)
add to favorites email to friend print save as pdf

Related Stories

Australopithecus Sediba could be direct ancestor of Homo

Apr 20, 2011

( -- Last year Lee Berger from the University of the Witwatersrand and his team discovered the skeletal remains of two specimens they determined to be a new species of human called Australopithecus se ...

New species of early hominid found

Apr 06, 2010

( -- A previously unknown species of hominid that lived in what is now South Africa around two million years ago has been found in the form of a fossilized skeleton of a child and several bones ...

Peking man differing from modern humans in brain asymmetry

Jun 28, 2011

Paleoanthropologists studying the fossil endocasts of Australopithecus, Homo habilis, Homo erectus, Neanderthals, and Homo sapiens have reported that almost all brain endocasts display distinct cerebral asymmetry. ...

New hominid shares traits with Homo species

Apr 08, 2010

Two partial skeletons unearthed from a cave in South Africa belong to a previously unclassified species of hominid that is now shedding new light on the evolution of our own species, Homo sapiens, researchers say. T ...

Family tree branches out

May 20, 2010

( -- UNSW anthropologist Dr Darren Curnoe has identified another new early human ancestor in South Africa ? the earliest recognised species of Homo.

Recommended for you

Egypt archaeologists find ancient writer's tomb

Apr 19, 2014

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

Crowd-sourcing Britain's Bronze Age

Apr 17, 2014

A new joint project by the British Museum and the UCL Institute of Archaeology is seeking online contributions from members of the public to enhance a major British Bronze Age archive and artefact collection.

Roman dig 'transforms understanding' of ancient port

Apr 17, 2014

( —Researchers from the universities of Cambridge and Southampton have discovered a new section of the boundary wall of the ancient Roman port of Ostia, proving the city was much larger than previously ...

User comments : 0

More news stories

Clippers and coiners in 16th-century England

In 2017 a new £1 coin will appear in our pockets with a design extremely difficult to forge. In the mid-16th century, Elizabeth I's government came up with a series of measures to deter "divers evil persons" ...

Growing app industry has developers racing to keep up

Smartphone application developers say they are challenged by the glut of apps as well as the need to update their software to keep up with evolving phone technology, making creative pricing strategies essential to finding ...

Making graphene in your kitchen

Graphene has been touted as a wonder material—the world's thinnest substance, but super-strong. Now scientists say it is so easy to make you could produce some in your kitchen.