Da Vinci and Geology, Fossils and the Bible

Leonardo da Vinci understood geology based on physical evidence he found. His studies of rocks, fossils, and river erosion led him to the conclusion that the world is far older than stated in the book of Genesis, and he argued that marine fossils found in the mountains were the result of falling sea levels, not the Great Flood.

He wrote:

And a little beyond the sandstone conglomerate, a tufa has been formed, where it turned towards Castel Florentino; farther on, the mud was deposited in which the shells lived, and which rose in layers according to the levels at which the turbid Arno flowed into that sea. And from time to time the bottom of the sea was raised, depositing these shells in layers, as may be seen in the cutting at Colle Gonzoli, laid open by the Arno which is wearing away the base of it; in which cutting the said layers of shells are very plainly to be seen in clay of a bluish colour, and various marine objects are found there.

A page of Leonardo's Paris Manuscript I is covered in sketches of marine fossils.

Among them is a honeycomb-like array of hexagons that palaeontologists think might constitute the first recorded observation of an enigmatic trace fossil called Paleodictyon.




He recognized fossils as petrified remains of former living organisms and even applied paleoecological principles to reconstruct the deposition of sedimentary rocks. Of course, he never published his notebooks and his theories were not well known during and for many years after his death.

Later, Nicolas Steno (1638-1686), with his stratigraphic principles, Robert Hooke (1635-1703), with his paleontological interpretation of fossils, and finally James Hutton (1726-1797), with his earth-theory, would make discoveries and theories that would have an impact on scientific thinking.

Walk This Way

A new study suggesting hominins were walking across a Greek island 5.7 million years ago is here to blow your mind. I have always been interested in following and identifying animal tracks, and I have had an interest in paleontology and evolutionary biology and anything related ever since I found a fossil when I was ten years old. So, of course, I was fascinated to see that multiple depressions preserved in a layer of 5.7 million-year-old sediment were found and they certainly look like they belong to a hominin, a member of our lineage. 

The site where they were found at Trachilos, on the Greek island of Crete. No hominin was thought to set foot there until millions of years later. 

Why do they think this (called Ardi) is hominin? Five forward-facing toes with the big toe in line (unique among primates) and the ball of the foot and a long sole which helps for walking long distances - and these tracks have those characteristics, though not as evolved as modern human feet. But the Discover blog points out that it is not that simple. 

Ardipithecus ramidus was walking around Ethiopia 4.4 million years ago. Ardi is considered a direct ancestor to the australopiths (you may have heard of "Lucy") and down the evolutionary road, us. But Ardi’s feet are much more ape-like with that big toe sticking out like a thumb. In other words, Ardi’s feet appear to have been more primitive than those of the potential Trachilos trekker, even though Ardi is more than a million years younger. 

The fossil record has so far told us that hominins evolved in Africa. If these are hominin footprints, they may have come from someone who originated either in Europe or Africa. The paper that revealed these "footprints" may be more scientific than you want, but here is the start of the abstract for "Possible hominin footprints from the late Miocene (c. 5.7 Ma) of Crete?"

"We describe late Miocene tetrapod footprints (tracks) from the Trachilos locality in western Crete (Greece), which show hominin-like characteristics. They occur in an emergent horizon within an otherwise marginal marine succession of Messinian age (latest Miocene), dated to approximately 5.7 Ma (million years), just prior to the Messinian Salinity Crisis. The tracks indicate that the trackmaker lacked claws, and was bipedal, plantigrade, pentadactyl and strongly entaxonic."

Another paper was published based on the discovery of a few teeth more than 7 million years old found in Greece and Bulgaria. They might also be hominin. Might be.

Doubters may ask how we even know that the tracks are that old. They are dated by analyzing marine microfossils in layers of rock above and below them. The authors of the study point out that these were tracks made when you could walk all of Africa and into Europe without getting your feet wet.

A friend who I talked with about all this laughed and said "You believe too much in science, which always seems to turn out to be wrong."  No, I would argue, science is conservative. It wants evidence, and it will easily admit to error when new evidence is found. We know a lot about evolution, but we are still learning.