Life on earth 3.4 billion years ago
Johannesburg - Geologists working on ancient South African rocks have proved that there was life on earth about 3.4 billion years ago.
And these life forms relied on sunlight to live - a discovery that reconfirms a theory ditched by scientists in the past.
The find, to be announced on Thursday in the science journal Nature, was made by Michael M Tice and Professor Donald R Lowe of Stanford University in the United States.
Studying fossilised micro-organisms taken from 3.8-billion-year-old sedimentary rock at Barberton, the geologists found evidence of early life in the rocks of structures and texture that resemble mats made from blue-green algae.
"They were able to prove that during the Archaean age about 3 400 million years ago there was some form of life around," according to South African geologist, Nicolas Beukes, who assisted the two locally.
Barberton is one of only two known locations worldwide of rocks formed in the shallow waters of an open ocean system more than 3 billion years ago - long before humans began inhabiting the earth about two million years ago.
In 1987 the discovery of micro-organisms on similar rocks by Bill Schorf, an American scientist studying fossils at Pilbara in western Australia, first gave rise to the theory.
"This was big news," recalled Beukes. "He suggested that the micro-organisms were making oxygen and releasing it into the atmosphere."
However, the theory was then discredited by another scientist, Martin Brasier, who argued these fossils were not "true" fossils and "without biological origin," Beukes explained.
The latest findings by Tice and Lowe have now forced scientists to revert to Schorf's original analysis.
"This study proves that yes, indeed there was life early one.
Microbial organisms were the start of everything and developed into everything we have on earth today," he explained in an interview with Deutsche Presse-Agentur, dpa.
The new discovery also showed that the early life forms depended on sunlight to exist, the scientist pointed out.
"They could also show that these organisms used the sun to get their energy and that is also very important. From photosynthesis comes oxygen," he told dpa.
"We are now back to believing that definitely early on there was life and the metabolic pathway of photosynthesis was in place," said Beukes. - Sapa-dpa