World's oldest fossils, or no such thing?

Researchers say they have found "compelling" new evidence of the earliest known forms of life on Earth in ancient rock in Australia.

Australian and Canadian scientists say they have found new varieties of stromatolites, rock formations left 3.43 billion years ago in the Pilbara region of Western Australia.

If the researchers are right, and the stromatolites represent the fossilised remains of early microbes, this could cause scientists to revise estimates of when life began on Earth; some estimates are as recent as 1.9 billion years ago.