The miracle of life
3,5 billion years ago, the inanimate became animate : from rocks, water and air, living beings capable of reproduction, regeneration and travelling by their own means appeared on Earth.
The most ancient traces of life have been found in Australia and South Africa.. Though distant from each other of 10,000 km, these two countries used to form one single supercontinent.These traces - the stromatolites - have the shape of rounded and flaky cushions. They were made by cyanobacteria , a branch of bacteria of which more than 7,500 species are known.
How to explain the miracle of life ? It used to be thought to have an extraterrestrial origin or that it had appeared in calm waters, where energy released by lightnings might have enabled chemical reactions.
A new hypothesis was put forward following the discovery of the « black smokers » in the ocean depths in 1977. These hydrothermal vents reject metal-laden hot water : they cater bacteria in addition to a food chain thriving independently from sunlight. It is thought that there are thousands of such smokers in existence and that they are the very place where life first appeared.
In shallow waters, like in Shark Bay, Australia, cyanobacteria activity allows for the accumulation of minerals which, century after century, generate stromatolites.
