From 2003 to 2005, when Abigail Allwood was a graduate student in earth science at Macquarie University, she made a series of remarkable discoveries. She was doing fieldwork in Western Australia's Pilbara region, where she was charged with studying fossilised stromatolites, or columns of sedimentary rock originally created by layers of microbes – some of the planet's first known life.

The area, a 196,000-square-mile expanse of rust-coloured desert populated with rock formations dating back more than 2 billion years, is more or less what you might picture when someone says "the ends of the Earth". Parts of it remain virtually untouched by humans. Allwood recalled for me recently how one day she and Ian Burch, then her research partner (now her husband), hiked the length of a high, narrow ridge some 10 miles long. "I'm pretty sure we were the only people that had been there for thousands of years," she told me. "I remember a northern quoll [a rat-like marsupial native] coming right up to us to take a closer look. It had never seen a human being before, so it wasn't afraid."

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