Fresh Science

Forget meteorites. Bin volcanic eruptions. When it comes to mass extinction continental drift is the mega-killer, claims Australian palaeontologist Dr Malte Ebach.

He argues that the “dance of continents”-the break-up, movement, collision and re-formation of continents through time-creates the basic geographic and climatic conditions which drive the decline and extinction of species.

“I bet that if you take a close look at the Cretaceous extinction you’ll find that the dinosaurs were already on the way out before the well known meteorite impact,” says Dr Ebach, who is about to take up a post-doctoral position with London’s Natural History Museum (NHM).

The cause: habitat destruction, courtesy of continental drift.

“Visualise two continents such as India and southern China colliding into each other, and consider the amount of destruction-coastlines will be turned into mountains and deep oceans into shallow seas,” he says, adding that with so much habitat loss, many species will decline and ultimately vanish.

Dr Ebach bases his surprising idea about the extinction of species-not to mention their birth and evolution-on a powerful new technique called “area cladistics”. He created the technique in collaboration with the NHM’s Prof Christopher Humphries.

Dr Ebach will explain area cladistics, its applications and some surprising results at a media conference at 12 noon at the Melbourne Museum.

“Area cladistics combines the relationships between many organisms with the places in which they are found, revealing geographical patterns in time,” Dr Ebach says.

“These patterns tell us about where the continents were located when these extinct animals lived and the journeys their fossil remains have undergone as they hitched a ride on the back of mobile continents.”

As an example, Dr Ebach points to his study of 400 million year old trilobites, small marine invertebrates which lived about 590 to 250 million years ago. Their remains are found worldwide.

Dr Ebach measured thirty different features on the heads of 100 individual trilobites from what is now Africa, North American, South American, China, Europe and eastern Australia.

He fed the data, along with the location where each trilobite was found, into a specially designed computer program.

The program identified the “patterns of similarity” and then built a branching diagram, showing the degrees of relationship between the trilobites and their geographical home as relative distance.

Dr Ebach and Prof Humphries reported in the April 2002 edition of Journal of Biogeography that trilobites living in what is now the southern and central United States were much closer to eastern Australian trilobites than those from Africa or South America.

“They moved right around the world to the other side from where they had been originally placed geographically,” he says. “That suggests that the generally accepted position of the ancient landmasses of Gondwanna and Laurentia are wrong.”

According to Dr Ebach, his study demonstrates that area cladistics works…that continental drift can be tracked without using conventional geological data which is often unreliable or absent.

Dr Ebach says the technique will enable scientists to investigate the movement of continents, the surface area of coastlines and the biodiversity of ancient life. The results promise to be immensely important.

“We will be closer to understanding the Earth processes that have been responsible for wiping out thousands of species in a geological twinkling of an eye,” claims Dr Ebach.

He is one of sixteen young scientists presenting their discoveries to the media, public and students for the first time, at Fresh Science.

“We’ve selected them from 105 national nominations, brought them to Melbourne, trained them and thrown them to the [media] lions,” said Niall Byrne, Chairman of Fresh Science. “It’s all about focussing public and media attention on Australian scientific achievement.”