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Nicolas Steno is rarely heard of

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outside Intro to Geology,

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but anyone hoping to understand life on Earth

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should see how Steno expanded and connected

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those very concepts:

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Earth, life, and understanding.

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Born Niels Stensen in 1638 Denmark,

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son of a goldsmith,

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he was a sickly kid

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whose school chums died of plague.

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He survived to cut up corpses

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as an anatomist,

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studying organs shared across species.

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He found a duct in animal skulls

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that sends saliva to the mouth.

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He refuted Descartes' idea

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that only humans had a pineal gland,

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proving it wasn't the seat of the soul,

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arguably, the debut of neuroscience.

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Most remarkable for the time was his method.

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Steno never let ancient texts,

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Aristotelian metaphysics,

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or Cartesian deductions

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overrule empirical, experimental evidence.

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His vision, uncluttered by speculation or rationalization,

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went deep.

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Steno had seen how gallstones

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form in wet organs by accretion.

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They obeyed molding principles

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he knew from the goldsmith trade,

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rules useful across disciplines

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for understanding solids

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by their structural relationships.

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Later, the Grand Duke of Tuscany

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had him dissect a shark.

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Its teeth resembled tongue stones,

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odd rocks seen inside other rocks

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in Malta and the mountains near Florence.

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Pliny the Elder, old Roman naturalist,

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said these fell from the sky.

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In the Dark Ages,

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folks said they were snake tongues,

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petrified by Saint Paul.

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Steno saw that tongue stones were shark teeth

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and vice versa,

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with the same signs of structural growth.

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Figuring similar things are made in similar ways,

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he argued the ancient teeth

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came from ancient sharks

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in waters that formed rock around the teeth

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and became mountains.

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Rock layers were once layers of watery sediment,

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which would lay out horizontally,

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one atop another,

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oldest up to newest.

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If layers were deformed,

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tilted,

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cut by a fault or a canyon,

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that change came after the layer formed.

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Sounds simple today;

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back then, revolutionary.

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He'd invented stratigraphy

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and laid geology's ground work.

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By finding one origin for shark teeth from two eras

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by stating natural laws ruling the present

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also ruled the past,

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Steno planted seeds for uniformitarianism,

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the idea that the past was shaped by processes

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observable today.

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In the 18th and 19th centuries,

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English uniformitarian geologists,

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James Hutton and Charles Lyell,

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studied current, very slow rates

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of erosion and sedimentation

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and realized the Earth had to be way older

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than the biblical guestimate, 6000 years.

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Out of their work came the rock cycle,

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which combined with plate tectonics

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in the mid-twentieth century

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to give us the great molten-crusting, quaking,

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all-encircling theory of the Earth,

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from a gallstone to a 4.5 billion-year-old planet.

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Now think bigger,

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take it to biology.

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Say you see shark teeth in one layer

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and a fossil of an organism

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you've never seen under that.

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The deeper fossil's older, yes?

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You now have evidence

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of the origin and extinction of species over time.

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Get uniformitarian.

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Maybe a process still active today

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caused changes not just in rocks but in life.

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It might also explain similarities and differences

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between species

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found by anatomists like Steno.

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It's a lot to ponder,

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but Charles Darwin had the time

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on a long trip to the Galapagos,

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reading a copy of his friend Charles Lyell's

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"Principles of Geology,"

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which Steno sort of founded.

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Sometimes giants stand on the shoulders

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of curious little people.

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Nicolas Steno helped evolve evolution,

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broke ground for geology,

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and showed how unbiased, empirical observation

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can cut across intellectual borders

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to deepen our perspective.

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His finest accomplishment, though,

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may be his maxim,

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casting the search for truth

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beyond our senses and our current understanding

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as the pursuit of the beauty

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of the as yet unknown.

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Beautiful is what we see,

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more beautiful is what we know,

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most beautiful, by far, is what we don't.