Scientists closer to finding origins of life

Popular theories on the origins of life have focused on the ancient ocean environment.

Scientists have developed an experiment which demonstrates how the very first life may have formed about four billion years ago.

John Sutherland and colleagues at Manchester University have broken new ground by being able to synthesise almost from scratch two of the four building blocks of RNA, the self-replicating molecule that many scientists believe to be the most likely contender for the original molecule of life.

Dr Sutherland believes that he has shown how it was possible to make all the building blocks of RNA from the simple chemicals that would have existed on Earth four billion years ago.

"We've made the building blocks of RNA from what was around on the early Earth and is still around in interstellar space and in the atmosphere of Saturn's moon Titan," Dr Sutherland said. "We haven't yet made the RNA molecule itself but we've made two of the four sub-units or building blocks. It suggests that making the molecule is possible," he said.

RNA is the less familiar cousin of DNA, the genetic blueprint of life. Like DNA, the RNA molecule can carry and transmit information from one generation to the next. But unlike DNA, RNA is a relatively simple molecule that many scientists believed could have been quite easy to synthesise in the harsh environment of the early Earth.

The trouble with this idea - which is more than 40 years old - is that no one has been able to join up the three components, the sugars, bases and phosphates that make up the four building blocks of RNA, under the sort of conditions that existed four billion years ago. Dr Sutherland, however, has shown in a study in the journal Nature that this is indeed possible.

"The trouble is, the human eye sees the three components of RNA and so the human brain assumes that to make the molecule you should combine those three components. People have found that they can make the sugars and the bases but the key thing they can't do is to join them together," Dr Sutherland said.

"We've just changed the order of assembly of the pieces, but it's overcome the dogma that it cannot be done."

In trying to explain how life began on Earth, scientists have attempted to formulate theories to account for how the first self-replicating molecule came into existence. One of the earliest theories was the "primordial soup", where simple molecules mixed together in a broth that was regularly energised by ultraviolet light and electric storms.

Over time, these molecules would have combined to form more complex substances containing the all-important ingredients of life - oxygen, carbon, hydrogen and nitrogen. Although scientists were able to make the building blocks of proteins in this way, they failed to do the same with DNA or RNA.

Thomas Cech at the University of Colorado and Sidney Altman at Yale found that RNA could act as a catalyst by speeding up a chemical reaction and yet being unchanged in the process.

This was the first hard evidence that RNA, a molecule that can replicate and store genetic information, could also have triggered the first synthesis of life's proteins.

- INDEPENDENT