October 19,1998

Indian find pushes the date back on evolution.

By Subhadra Menon

The has always dug around for fossils. But this time, along with two German scientists, P.K. Bose has made a "staggering" find. That's what experts across the globe are saying. The unassuming professor from Jadavpur University in Calcutta has unearthed traces of complex multicellular animals, providing evidence that they existed much, much earlier than what was believed till now. From Bose's discovery on a roadside in Churhat, a town in Madhya Pradesh, it is now being inferred that such animals evolved 1,100 million years ago, not 570 million as widely believed.

The Churhat finding has been published by Bose in the October 2 issue of Science-a prestigious American journal. For the first time, there is hard proof for what molecular biologists voiced all along: that multicellular animals first showed up a billion years ago and then gradually evolved into bigger life forms. Scientists call it the slowburn theory of evolution.

The other theory for which there was evidence-570 million-year-old fossils found in China recently-suggested the "big bang" where a variety of organisms originated suddenly, leaving their mark on fossil records. But this hinged on the belief that there were no multicellular creatures in rocks older than 570 million years. Bose's spadework has changed all that.

Scientists at the Wadia Institute of Himalayan Geology in Dehradun concede this is a very significant finding. Using refined fission track and potassium-argon dating techniques, Bose and his collaborators have established that the twisted tracks on Churhat's typical sandstone must have been ancient worm-like animals. Since shallow seas covered central India that long ago, these animals must have spent their lives burrowing in the sandy seabed. When the beds slowly turned to solid rock about 1.1 billion years ago, the animals got preserved forever. And what's left of them are these tracks called trace fossils.

But what do the sceptics say? Some point out that Bose's sandstone twistings could very well have been formed by the general wear and tear that constantly occurs in the bowels of the earth. But there are other questions. Bose has used the Churhat rocks (which are said to be about a billion years old) to place the fossils in time. However, the very age of these rocks is in question. Says Prabha Kalia, head of the geology department, Delhi University: "All of it is still in the realm of debate." Bose refutes both points. The measurements of these twistings are consistent with multicellular organisms, he says. "As for the Churhat rocks, the age which they date back to is universally accepted," he adds.

For him, the findings have come after a long search. For decades, he and his team have been studying fossils in Churhat. The first time he saw these patterns, he wondered if they were ancient plant roots or termite tracks. But last year, armed with sophisticated equipment, these very patterns revealed a different truth. Of a kind that might rewrite history.

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