Leonardo da Vinci was not just a great painter. He was also a brilliant geologist, as today's latest instalment of our interactive series on his drawings reveals. Rocks pile and gather and disintegrate in mountains, caves, strata and screes in his paintings. The two versions of his picture The Virgin of the Rocks in the National Gallery's exhibition of his art glory in two different imaginary caverns, each with its own rich earthscape of stone perforated and sculpted by wind and water. But Leonardo did not only look at stone from a painter's point of view. It was not a background feature in his eyes. It was a scientific problem.

As a geologist, Leonardo anticipated the scientists of the 18th and 19th centuries who were to prove that the Earth is far older than it says in the book of Genesis. When scientific pioneers around 1800 recognised fossils for what they are – traces of ancient animals – and analysed the processes that create and erode rocks, they quickly reached a set of conclusions that led to Darwin's theory of evolution and a crisis of Christianity. But amazingly, a self-taught researcher called Leonardo da Vinci thought through a lot of their key discoveries hundreds of years earlier.

Leonardo had the following astonishing insights about geology and fossils:

1) Shells that appear on mountain tops and fish bones in caves must be the remains of animals that long ago swam in these places when they were covered in sea. The claim they were swept there by the biblical flood is a completely inadequate explanation. So the surface of the earth has changed over time, with land where once there was sea.

2) The most powerful natural force is the movement of water in rivers. Water has sculpted the very largest features of the landscape, a process that must have taken a very long time.

3) Therefore slow and relentless natural processes, not the divine instantaneous act described in Genesis, have shaped our planet.

The quotations from Leonardo's notebooks in our interactive today show him puzzling over these basic problems of science and reaching some of his radical conclusions. He did not merely think about these things in the abstract – he did real research. When he lived in Milan as court artist to Ludovico Sforza he was conveniently close to the Alps. He went walking in the mountains and climbed to the top of Monte Rosa. He writes in his notes about exploring a mountain cave where he found massive fossil bones, and reveals that he was famous for this interest in rocks and strange forms hidden within them: one day, he says, when he was living in Milan, some peasants brought him a sack full of seashells they had found in the mountains.

Centuries later, Leonardo's recognition that fossils tell the true story of the Earth would be rediscovered by science and this insight would overturn religious views of creation. But creationists who still try to argue against the evidence of the rocks should know that it was not Darwin who struck the first blow against biblical views of nature. It was Leonardo da Vinci, as you can see in our interactive guide to one of his great geological drawings.