Back in the 18th century, most scholars believed that the Earth had been created about 6,000 years previously and that it hadn’t changed much in that time, with mountains, rocks and lakes still sitting pretty much where God had placed them.

However, Scottish geologist James Hutton disagreed. And in challenging the prevailing orthodoxy, he set the scene for Darwin’s theory of evolution.

Hutton thought that the Earth was more dynamic than theologians would have it, and spent decades travelling Britain in search of evidence. “Lord pity the arse that’s clagged to a head that will hunt stones,” he wrote during one particularly arduous leg on horseback.

He discovered sites where strata meet at right angles, where older rocks overlaid younger ones, and, in Holyrood Park in his home city of Edinburgh, a small cliff that became known as ‘Hutton’s Section’. Here he observed that lava had penetrated the existing sedimentary rock layer.

It all pointed to the conclusion that the Earth’s crust was constantly recycling itself. Earthquakes and volcanic activity turn ocean floors into mountains, which erode into sediment, which settles on the seabed to become rock once again. And because it all happens very, very slowly, the planet must be extraordinarily old.

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Hutton did not actually put a figure on its age. Instead he talked of “deep time”, in which “we find no vestige of a beginning – no prospect of an end”.

These insights earned Hutton the sobriquet “the father of modern geology”, but he was also an influential uncle of modern biology. He provided the timeframe necessary for evolution to work its magic; it was then left to Darwin to work out the mechanism.

Main image James Hutton © Henry Raeburn, Public domain, via Wikimedia Commons