Microbes built ancient rocks in Australia

Odd-shaped rocks in the Pilbara region of Western Australia offer compelling evidence they were built by microbes 3.43 billion years ago, scientists say.

The structures, known as stromatolites, could only have taken the forms they have if bacteria had been present, a Sydney-led team tells Nature journal.

The rocks' origin is disputed, with some claiming purely chemical processes could have made them.

But the Nature study suggests the biological explanation is the simplest.