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  • From 1600 to 1800, European physics and chemistry went through revolutions that made them quantitative,

  • or numbers-based.

  • Meanwhile, biology remained with natural history, and stuck with observation-based knowledge.

  • But what about the study of the earth?

  • In this field, natural philosophers were asking questions like, what's up with fossils?

  • Are they the remains of extinct organisms?

  • Or are they so-calledsports of nature”—rocks that just happen to look like living things

  • but don't mean anything?

  • And most importantly, how old iseverything?

  • I gotta say, as disciplines of science go, this one has pretty much everything awesome

  • in it.

  • Vast eons?

  • Check.

  • Mega floods and supervolcanoes?

  • Got those!

  • Dinosaurs?

  • Uh, huh!

  • A hunt for living mastodons?

  • Buddy, you know it.

  • Geology, paleontology, oceanography, meteorology, and othersthe earth sciences are fascinating,

  • and so is their history.

  • Let's rock!

  • [OPENING MUSIC PLAYS]

  • If you're looking for the foundations of

  • geology, one place to start is with mining.

  • Archaeologists have shown, for example, that indigenous populations around the Great Lakes

  • mined and used the copper near modern-day Lake Superior for over six thousand years.

  • And in Europe, mining took off along with colonization.

  • In the sixteenth century, colonial empires exploited the precious metals of Central and

  • South America, relying on the geological knowledge and technical skills of indigenous communitiesnot

  • to mention their labor.

  • But, despite gathering a lot of new data about the Earth in this way, natural philosophers

  • kept banging their heads against one question: how can we reconstruct the earth's history,

  • or geohistory?

  • No one could confidently know the age of the earth before the discovery of radioactivity

  • and the development of radiometric dating in the early twentieth century.

  • Today, by the way, we think the earth is around 4.543 billion years old.

  • But since at least the seventeenth century, people have compared layers of rock and declared

  • them younger or older, depending on their positions relative to other layers.

  • This was a qualitative, or value-based practice: it was hard to date rocks just by looking

  • at them.

  • But this didn't stop people from trying.

  • In seventeenth-century Europe, it was commonplace to believe that the age of the earth and the

  • age of human species were about the same.

  • So to know the age of the earth, historians tried to create a quantitative chronology

  • of human history.

  • This meant comparing all known ancient sourcessuch as texts from China, Greece, or Babyloniaas

  • well as things like the records of eclipses and comets.

  • All these events were placed into a detailed chronology: a linear narrative that ran from

  • the creation of the universe to the present.

  • In 1654, Bishop James Ussher—a scholar and the top religious leader of Irelandcalculated

  • the age of the earth to be about six thousand years old, based on textual evidence from

  • the bible.

  • Other historians reached different conclusions and argued over the reliability of different

  • sources, but in general they reached a date for the beginning of time somewhere around

  • 4000 BCE.

  • By the late seventeenth century, some European naturalists, such as polymath Robert Hooke,

  • argued that natural objects, like fossils, should also be used like historical texts to

  • shed light on early human environments.

  • For example, many believed that the biblical Flood had scattered organic remains globally,

  • which explained why we can find seashells on the tops of mountains.

  • This attention to fossils would set the stage for new theories of organic development, such

  • as those of Charles Darwin.

  • Between Hooke and Darwin, several eighteenth-century

  • French thinkers played a critical role in speculating about fossils and finding ways

  • to calculate the age of the earth.

  • These were theTransformistnatural historians who developed proto-evolutionary

  • theories.

  • The Comte de Buffon, for example, argued that the earth was progressively

  • cooling.

  • According to Buffon, during this cooling process, the earth underwent phases orepochs,”

  • which were roughly parallel with the six Biblical days of Creation from the book of Genesis.

  • And since humans appeared only in the seventh and final epoch, Buffon's history of the

  • earth was mostly pre-humanwhich was a totally new idea!

  • To determine the age of the earth, Buffon conducted what might be described ascooling

  • experiments.

  • He timed the rate at which heated balls of different sizes and materials cooled down.

  • Publicly, Buffon estimated the earth was around seventy-five thousand years old.

  • But privately, based on his experiments, he speculated that it was up to ten million

  • years old!

  • So, although most European geologists in the 1700s were devout Christians, they foundlike

  • Buffonthat the Genesis narrative could be read as more of a metaphor that complemented,

  • rather than contradicted, scientific evidence.

  • This allowed Christian thinkers to come to terms with a vast, pre-human history.

  • Still, fossils remained a questionable form

  • of evidence for understanding the history of Earth.

  • Did they represent the remains of pre-human worlds, or were those creatures still roaming

  • wild spaces somewhere?

  • Georges Cuvier thought he had the answer.

  • Help us out, ThoughtBubble:

  • Cuvier argued that each epoch of earth history had its own distinctive flora and fauna.

  • And these epochs were separated by global catastrophes such as tsunamis, meteorites,

  • or earthquakes.

  • Life forms did not persist after the catastrophes, he thought.

  • They went extinct with the end of their worlds.

  • We call this theory catastrophism.

  • And according to it, fossils reveal a linear sequence, which can be used to reconstruct

  • the earth's past.

  • This wasn't a new idea: in 1696, for example, William Whiston published A New Theory of

  • the Earth from its Original to the Consummation of All Things.

  • And in it, he attempted to explain the history of earth in terms of catastrophes, too.

  • Like, Whiston thought that a comet hitting earth must have caused the Flood of Noah.

  • What Cuvier did differently was amass fossil evidence of changes in organisms.

  • Studying the geology of central France, Cuvier noticed gaps where the fossils would simply

  • disappear, only for new kinds of fossils to appear a little bit higher up, in new layers

  • of rock.

  • He recognized these gaps as extinction events.

  • To make things easier, Cuvier decided to focus on really big bones

  • mastodon and mammoth skeletons.

  • He figured these animals would be hard to miss if they were still roaming the earth.

  • (Spoiler: they were, in fact, extinct.)

  • But Cuvier compared the teeth of elephants and those of other animals like them.

  • And in doing that, he established that African and Indian elephants are different species,

  • and that mammoths were not the same as either of them.

  • Thanks ThoughtBubble.

  • Now, how did Cuvier get all of these fossils?

  • Well, the new Revolutionary government in Paris secured Cuvier a position at the

  • Museum of Natural History, which gave him the power to establish a global fossil delivery

  • service for other natural philosophers.

  • So, those big mastodon fossils that he studied came from North America.

  • And it's worth pointing out that, because of that, Cuvier became fascinated with Native

  • American ideas about creation and extinction.

  • He went out of his way to buy fossils from tribes such as the Iroquois, Shawnee, and

  • Lenape to learn what they thought about these old, gigantic bones in the ground.

  • Cuvier couldn't have come up with new theories about fossilsor even collected so many

  • fossilswithout the help of many indigenous knowledge makers.

  • So by 1800 or so, geologists had reached a consensus on some wild ideas: the earth had

  • undergone gradual change over an incredible amount of time before the appearance of

  • humans.

  • And Earth's history was punctuated by sudden episodes of violent change.

  • Life had either adapted to new environments or gone extinct.

  • And so the fossil record was progressive: wimpy little trilobites died out, and humans

  • came into the story at the end, ready to build robot musicians.

  • But not everybody loved Cuvier's theories.

  • Scottish geologist Charles Lyell instead argued for a slow, “steady-statetheory of geological

  • change that would become known as uniformitarianism.

  • He famously had two specific bones to pick with Cuvier.

  • First, Lyell thought the French had relied too much on catastrophes to explain geological

  • history.

  • He argued that observable geological processeslike erosion and deposition caused by wind, rivers,

  • rain, or the occasional volcanic eruptionwere the only explanations that geologists should

  • consider reasonable or scientific.

  • Second, Lyell argued that extinctions were spread evenly across geological timenot

  • clustered together in mass-extinction events.

  • This steady extinction rate was balanced, he thought, by the steady creation of new

  • species, according to global climate conditions.

  • So, for Lyell, geohistory wasn't linear, but cyclical and ... uniform.

  • It pretty much worked the same in each epoch.

  • Lyell's big book, Principles of Geology, published from 1830 to 1833, became a Principia

  • for earth scientists.

  • And I should note here that we've been saying "Prince-uh-pee-uh"

  • for the whole History of Science so far

  • But, one of our writers is in the room and has told us it's "Prin-KIP-ee-uh."

  • In 'Principles of Geography" he argued that the earth is immensely old, and that, as he put it, “the present is

  • the key to the past.”

  • The debate between catastrophism and uniformitarianism would go on for a long time.

  • But while Lyell's position on extinctions was dismissed by older geologists as too extreme,

  • his emphasis on the power of gradual change inspired many younger scientists.

  • One of them was Charles Darwin, who read Lyell's books and later became his good friend.

  • Lyell could never quite figure out how fossils and living organisms were related, but

  • like, for now, get out of here, Chuck!

  • We're gonna get to you in a couple episodes.

  • Another influence on Darwin, in the realm

  • of fossil collecting, was Oxford geologist William Buckland.

  • Buckland led trips to caverns and abandoned mines, where he found remains like cave bear

  • bones from the Pleistocene.

  • For evidence of even more ancient life, we turn to English paleontologist Mary Anning.

  • Anning walked the beaches after storms to find and excavate fossils, which she then

  • sold, mostly to Buckland.