Research uncovers wormhistory

Newsday

A close new look into Earth's deep past shows that for a very, very long time, life on this planet may have been distinctly wormy.

The discovery of worm tracks on ancient sediments in India suggests that small worms, perhaps the first complex life forms, began burrowing through mud on Earth 1.1 billion years ago.

If true, that would place the beginning of multi-cellular life on our planet twice as early as scientists previously calculated, said Yale University paleontologist Adolf Seilacher, who reports the research this week in Science magazine.

The surprising new evidence was discovered in ancient, sandy sediments in central India.

Seilacher said he went to India in 1996 "to show that the things described there were not burrows."

But he found the burrows are real, formed in a layer of soil just beneath a layer of marine bacteria in shallow water.

In that protected environment, he said, the worms - which were about as thick as a drinking straw - apparently dined on the remains of dead bacteria, breathing oxygen released into the soil by the bacteria.

No remains of the worms were found.

"If this report is true, it is spectacular," said paleontologist William Schopf, at UCLA. Schopf studies the earliest known fossils on Earth, algal remains called stromatolites.

Fossil evidence has long shown that something important happened 540 million years ago, when the so-called "Cambrian Explosion" of biological diversification took place.

That is the period when most species known today arose, but scientists have never really determined what caused the dramatic change.

Before then, the researchers said, the "diversification of animal designs proceeded very slowly."

But afterwards, there was an intense burst of evolution leading to the humans, lions, elephants, cats, dogs and other beings that inhabit the Earth today.

Although the idea is speculative, Seilacher said, it may be that by 540 million years ago enough oxygen had finally accumulated in the air to allow more complex forms of life to develop, and then spread to inhabit the entire globe.

Oxygen metabolism provides a substantial energy boost.

Seilacher, professor emeritus in Tubingen, Germany, worked on the research with two colleagues, sedimentologists Pradip Bose, in Calcutta, India, and Friedrich Pfluger, in Reutlingen, Germany.

10-01-98