Saturday 09 December, 2000
The Garden of Ediacara
Life on Earth has a four billion-year history, culminating, it seems, in ourselves. For most of that time, the planet was ruled by little more than bacteria and pond scum. Then some spectacular changes began to happen that transformed both life and the environment in which it lived.
For Life Story, producer Martin Redfern travels the world in search of fossils that record key events in the history of life. Over the next four weeks he reports on his journeys of discovery. The story begins in Australia where strange giant worms and creatures that look like floating airbeds suddenly joined the microscopic algae.
We dined on seared kangaroo at a surprisingly good restaurant for such a remote part of the Flinders Range National Park in South Australia, about 500 kilometres north of Adelaide. Then we headed on northwards in darkness over dirt tracks to a secret destination. My guide, Dr Richard Jenkins of Adelaide University, insisted that we should rough it in the sheep shearers’ accommodation so that we could begin our hunt at dawn.
The effort of rising in twilight was amply repaid with a magnificent sunrise. It was not that our quarry was nocturnal. In fact the creatures had been dead for 550 million years. But the low angle light of morning would throw their faint imprints in the reddish quartzite rock into sharp relief. As the sun rose higher they would vanish with the shadows, to be replaced by flies and heat.
Ediacara fauna
Soon, I began to spot them: concentric circular patterns on the ripple-marked slabs. At first people thought they were jellyfish, then they were found to be the holdfasts of delicate fronds of a sort of soft coral. We found a couple still attached to their leathery stems. Other fossils littering the hillside are more enigmatic, including a quilted or segmented oval called Dickinsonia.
The ones I found were 10 or 15 centimetres long but specimens up to metre are known and this site is particularly rich in them, known among the palaeontologists as Dickinsonia Gulch. I could well see why Richard Jenkins wanted to keep the precise location secret to protect it from casual fossil collectors and the professional rustlers who would sell fossils in the USA or Japan for considerable sums, robbing both the site and science.
| 'These are very special fossils. Apart from a few questionable worm tracks, they are the oldest evidence of large animals on earth.' | |
Named collectively after the nearby Ediacara Hills, the Ediacara fauna has been found not only here in Australia but in Namibia, Russia, Mexico, and Canada - the list goes on. But no one was quite sure what they were.
Flatworms
It is tempting to try and find similarities with present-day marine creatures. Many researchers, including Richard Jenkins think that Dickinsonia, for example, may have been a distant cousin of flatworms, with its segmented body and a gut for digesting the slimy bacteria it grazed from the shallow sea floor. Others, notably Dolf Seilacher of Tubingen and Yale believe they were in entirely different class of organism either from plants or animals, inflated bags of jelly like air mattresses, possibly containing symbiotic bacteria to help them harness nutrients and sunlight.
Either way, they would never survive today. They were like great-unprotected slabs of meat with no hard parts for protection. Five hundred and fifty million years ago they needed no defence. This habitat has been likened to the Garden of Eden, a peaceful world with no predators. But it did not last long. Twenty five million years later you only find the fossils of creatures with shells, jaws or claws or an ability to burrow and hide.
As we were leaving, I stopped to photograph the disk of one last soft coral. There in my viewfinder next to it I scarcely noticed a small trace about three centimetres long. Richard Jenkins seized it excitedly. He suspects that it could be a representative of one of the few groups to survive the Ediacara: a primitive ancestor of vertebrates including ourselves. But Ssshh; it’s not published yet!
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Ediacara Fauna is the animal life that lived in the Ediacaran period (approx. 650-544 million years ago).
Named after the Ediacara Hills in Australia, the early animal fossils were first found in 1946, by the Australian mining geologist Reginald C.Sprigg.
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