Here’s a story you might have read before in a popular science book or seen in a documentary. It’s the one about early Earth as a lifeless, volcanic hellscape.

When our planet was newly formed, the story goes, the surface was a barren wasteland of sharp rocks, strewn with lava flows from erupting volcanoes. The air was an unbreathable fume of gases. There was little or no liquid water. Just as things were starting to settle down, a barrage of meteorites tens of kilometres across came pummelling down from space, obliterating entire landscapes and sending vast plumes of debris high into the sky. This barren world persisted for hundreds of millions of years. Finally, the environment settled down enough that oceans could form, and the conditions were finally right for microscopic life to emerge.

That’s the story palaeontologists and geologists told for many decades. But a raft of evidence suggests it is completely wrong.

The young Earth was not hellish, or at least not for long (in geological terms). And, crucially, life formed quickly after the planet solidified – perhaps astonishingly quickly. It may be that the first life emerged within just millions of years of the planet’s origin.

With hindsight, it is strange that the idea of hellscape Earth ever became as established as it did. There was never any direct evidence of such lethal conditions. However, that lack of evidence may be the explanation. Humans are very prone to theorise wildly when there’s no evidence, and then to become extremely attached to their speculations. That same tendency – becoming over-attached to ideas that have only tenuous support – has also bedevilled research into the origins of life. Every journalist who has written about the origins of life has a few horror stories about bad-tempered researchers unwilling to tolerate dissent from their treasured ideas.

Now that the idea of hellscape Earth has so comprehensively collapsed, we need to discard some lingering preconceptions about how life began, and embrace a more open-minded approach to this most challenging of problems. Whereas many researchers once assumed it took a chance event within a very long timescale for Earth’s biosphere to emerge, that increasingly looks untenable. Life happened fast – and any theory that seeks to explain its origins now needs to explain why.

One of the greatest scientific achievements of the previous century was to extend the fossil record much further back in time. When Charles Darwin published On the Origin of Species (1859), the oldest known fossils were from the Cambrian period. Older rock layers appeared to be barren. This was a problem for Darwin’s theory of evolution, one he acknowledged: ‘To the question why we do not find records of these vast primordial periods, I can give no satisfactory answer.’

The problem got worse in the early 20th century, when geologists began to use radiometric dating to firm up the ages of rocks, and ultimately of Earth itself. The crucial Cambrian period, with those ancient fossils, began 538.8 million years ago. Yet radiometric dating revealed that Earth is a little over 4.5 billion years old – the current best estimate is 4.54 billion. This means the entire fossil record from the Cambrian to the present comprises less than one-eighth of our planet’s history.

Stromatolites were well known, but these, from the Pilbara region in Western Australia, were astonishingly old

However, in the mid-20th century, palaeontologists finally started finding older, ‘Pre-Cambrian’ fossils. In 1948, the geologist Reg Sprigg described fossilised impressions of what seemed to be jellyfish in rocks from the Ediacara Hills in South Australia. At the time, he described them as ‘basal Cambrian’, but they turned out to be older. A decade later, Trevor Ford wrote about frond-like remains found by schoolchildren in Charnwood Forest in England; he called them ‘Pre-Cambrian fossils’. The fossil record was inching back into the past.

By 1980, the fossil record had become truly epic. On 3 April that year, a pair of papers was published in Nature, describing yet more fossils from Australia. They were stromatolites: mounds with alternating layers of microorganisms and sediments. In life, microbes like bacteria often grow in mats. These become covered in sediments like sand, and a new layer of cells grows on top, over and over. Stromatolites were well known, but these, from the Pilbara region in Western Australia, were astonishingly old. One set was 3.4 billion years old; the other looked like it might be even older, as much as 3.5 billion years old.

Over the past 45 years, palaeontologists have meticulously re-analysed the Pilbara remains to confirm that they are real. It’s not a trivial problem: with rocks that ancient, strange distortions can form that look like fossilised microbes but are actually just deformed rocks. To resolve this, researchers have deployed an array of techniques, including searching for traces of organic matter. At this point, we are as confident as we can be that the Pilbara fossils are real. That means life has existed for at least 3.5 billion years. When I wrote The Genesis Quest back in 2020, I said this gave us a billion-year time window after the formation of Earth in which life could form. Since then, the evidence for life has been pushed further back in time.

Until relatively recently, many researchers would have said the window was distinctly narrower than that. That’s because there were reasons to think that Earth was entirely uninhabitable for hundreds of........

© Aeon