Earth Science: Crash Course History of Science #20


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-called “sports of nature”—rocks
that just happen to look like living things but don’t mean anything? And most importantly, how old is… everything? 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 others—the 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 communities—not 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 sources—such
as texts from China, Greece, or Babylonia—as 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 Ireland—calculated 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 the “Transformist” natural
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 or “epochs,” 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-human—which was a
totally new idea! To determine the age of the earth, Buffon
conducted what might be described as “cooling” 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 found—like Buffon—that 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 fossils—or even collected so many fossils—without 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-state” theory 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 processes—like
erosion and deposition caused by wind, rivers, rain, or the occasional volcanic eruption—were
the only explanations that geologists should consider reasonable or scientific. Second, Lyell argued that extinctions were
spread evenly across geological time—not 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. In 1811, she even found a spectacularly well-preserved
ichthyosaur. Anning was a keen observer and talented nature
writer. An 1830 painting of “ancient Dorset” based
on her work brings to life an entire Jurassic… world (Universal Studios, please don’t sue
me!), filled with marine and flying reptiles. In the vision of Buckland and Anning, the
reptilian past was separated from the modern world by the Flood, after which humans were
created. The new theories about the earth, circa 1800,
all required what is perhaps the most important idea of earth science: “deep time,” or
“geological time.” This is the notion that, before humans, the
earth had already been around for an unimaginably long time. And this great expanse of time is, like human
history, full of sudden events and patterns that persist over epochs. So, deep time implies that geohistory can
be reconstructed in the same way that historians reconstruct the human past. Except, instead of relying on vases, ruins,
and letters, geo-historians rely on fossils, volcanoes, and rocks. This epistemic mode of thinking about the earth’s history emerged thanks to the technē
of industrializing Europe. And so the earth sciences became more regular
as professions in the late 1700s and early 1800s. In industrializing nations, governments and
landowners started investing in geological surveys and mining academies. In these academies, earth scientists were
trained to generate new ways to satisfy a world increasingly dependent on one mineral
resource, coal. New visual technologies for geological mapping,
and a new system for tracking rock groupings across vast distances, emerged from the works
of Abraham Gottlob Werner and his students at the mining academy in Freiberg, Germany,
in the 1770s. In Britain, mineral surveyors and civil engineers,
such as William Smith and John Farey, started using fossils to improve the accuracy of their
geological maps. This technique soon became standard practice. Smith was also one of the first people to
use a thematic map, a map showing something about the earth other than its shape, to classify
different rocks across Britain. And he was one of the first to use fossils
to map rock formations for practical ends, like civil engineering and mineral prospecting. His maps were very useful to the geologists
reconstructing the earth’s history: they helped fossil hunters arrange their finds
according to rock strata and thus age. Innovations created by Smith and others like
him set off a wave of geological exploration around the world, backed by governments and
industries. And, by the early 1800s, the industrial world
was gobbling up coal at an unprecedented pace… Quick note that this episode would not have
been possible without the expert advice of Gustave Lester, a Ph.D candidate in the Department of the History
of Science at Harvard University. Thanks, Gustave! Next time—the history of technology is going
to get steamy: that’s right, it’s the Industrial Revolution! Crash Course History of Science is filmed
in the Dr. Cheryl C. Kinney studio in Missoula, Montana and it’s made with the help of all
this nice people and our animation team is Thought Cafe. Crash Course is a Complexly production. If you wanna keep imagining the world complexly
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