CT study of early humans reveals evolutionary relationships

Date:

Share post:

CT scans of fossil skull fragments may help researchers settle a long-standing debate about the evolution of Africa’s Australopithecus, a key ancestor of modern humans that died out some 1.4 million years ago. The study, to be published in the Proceedings of the National Academy of Sciences, explains how CT scans shed new light on a classic evolutionary puzzle by providing crucial information about the internal anatomy of the face. 

Pictured are a photograph and CT scan of Sts 5, the most well-preserved specimen of Australopithecus africanus [Credit: Images courtesy of the Ditsong National Museum of Natural History, formerly the Transvaal Museum]

For decades scientists have disagreed about the significance of facial features shared by a number of Australopithecus species, and in particular two bony columns known as “anterior pillars” that extend up from the canine teeth and bracket the nasal opening. 

Dr Brian Villmoare (University College London and The George Washington University) and Professor William Kimbel (Arizona State University) analysed CT scans of fossil skull fragments from five Australopithecus species and found that beneath the skin the internal structure of the anterior pillars is quite different for different species. According to the authors, South Africa’s A. robustus and East Africa’s A. boisei had solid columns of dense, spongy bone tissue and were probably sister species, while A. africanus (also from South Africa) probably evolved in parallel as its pillars are simply hollow columns of bone. 

The authors argue that these structural differences show that anterior pillars evolved via different pathways in different species. The findings challenge long-standing theories that similar external facial features represent shared traits inherited from a common ancestor, and suggest instead that external similarities in South Africa’s A. africanus and A. robustus were due to parallel evolution. 

“We believe that the detailed similarities in the internal anatomy of the face strongly supports the hypothesis that there was a single evolutionary branch of ‘robust australopithecines’, and that the A. africanus and A. boisei forms both shared a common ancestor,” says Dr Villmoare. “The external similarity of the anterior pillar in other Australopith species may be related to convergence on a similar dietary niche, but does not seem to indicate shared ancestry.” 

The full article, ‘CT-based study of internal structure of the anterior pillar in extinct hominins and its implications for the phylogeny of robust Australopithecus’ is published in PNAS Online, Monday 19 September.  

Source: University College London [September 19, 2011]

1 COMMENT

ADVERTISEMENT

spot_img

Related articles

Stone Age artefacts found in Norway’s melting glaciers

Around 7,000 years ago the Earth was enjoying a warm climate. Now glaciers and patches of perennial ice...

Hubble sees a swirl of star formation

The Hubble Space Telescope has captured the image of an unusual galaxy -- a beautiful, glittering swirl named,...

Climate change could decrease Sun’s ability to disinfect lakes

Increasing organic runoff as a result of climate change may be reducing the penetration of pathogen-killing ultraviolet (UV)...

Assessing the impact of human-induced climate change

The past century has seen a 0.8°C (1.4°F) increase in average global temperature, and according to the Intergovernmental...

Ancient Chinese levee system set stage for massive, dynasty-toppling floods

For thousands of years, Mother Nature has taken the blame for tremendous human suffering caused by massive flooding...

Low quality genes may cause mutational meltdown

Evolutionary biologists at the University of Toronto have found that individuals with low-quality genes may produce offspring with...

New language discovery reveals linguistic insights

A new language has been discovered in a remote Indigenous community in northern Australia that is generated from...

New evidence from Babylonian destruction of Jerusalem

Evidence of the destruction of Jerusalem at the hands of the Babylonians is currently being unearthed in the...