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CHAPTER 11
3761
B.C.
In t he seventeent h century, Irish bishop James Ussher had calculat ed the
earth’s age from biblical genealogies: he concluded that God created the world on 24
October 4004
B.C.
At first, the influence of scrip ture inclined scientists to think along
the lines of a theory of catastr oph ism t o explain geology. According to this theory,
rare and unusual events of enormous power, resembling divine inte rven tion ,
explained the featur es of the earth . While the theory of catastrophism provided some
understand ing of the earth’s past, new discoveries soon called it into question.
Charles Lyell’s book Principles of Geology provided a new theory in 1829. Lyell
proposed the theory of uniformitarianism to explain the history of the earth,
saying that the same (uniform) processes shaping the earth today have always acted
to remold the planet. Thus, erosion and deposition, uplift and sinking of land-
masses, volcanoes, earthquakes, glaciers, and so on have formed every existing
landscape. He concluded that the earth was not fixed, but in flux. Since many of
these processes move infinitesimally slowly, the theory required that earth be at
least millions of years old.
Many Christian who interpreted the Bible literally opposed this new theory,
since these numbers contradicted calculations based on Genesis. Nonetheless, the
practice of science increasingly left God out of the equation. Indeed, most scientific
evidence collected over the nineteenth century clearly supported uniformitarian-
ism, while almost none backed up catastrophism. Uniformitarianism could, by mea-
surable natural processes, account for the highest mountain and the deepest valley.
Just as with theories of heliocentrism and universal gravitation, scientists embraced
the theory of uniformitarianism because it had explanatory power and conformed
to the evidence of nature.
Fossils provided much of the evidence for research into the earth’s history.
Scientists found petrified remains both of contemporary-looking organisms and of
strange creatures that did not seem to exist anymore. Excavations for mines, canals,
building foundations, and so on in the industrial age unearthed more and more
fossils. Scientists began to organize these fossilized bones and called the large crea-
tures dinosaurs (‘‘terrible lizards’’). As geologists compared layers of rock in which
fossils were found, science showed that dinosaurs had lived many millions of years
ago before becoming extinct. But how had those monsters, or many other life-
forms, died out, while others still seemed to be around?
A second phase of the Scientific Revolution was born as biologists tried to solve
that very mystery. The oldest layers of rock showed a few simple living things, such
as algae. More recent rock layers showed a connected diversity of life, as evidenced
by the appearance of new species (a scientific category of living things that could
reproduce with each other). As eons wore on, some species, like the dozens of
kinds of dinosaurs, had clearly gone extinct. Others, like ferns, clams, and cock-
roaches, had survived into the present with little change. The fossil record showed
that overall, life had become increasingly diverse and complex over time. Scientists
called this process of biological change evolution.
Christian religious literalists opposed evolution as vehemently as they earlier
had denied the age of the earth or, going back to Copernicus, located the earth at
the center of the universe. Evolution, the age of the earth, and the earth’s noncen-
tral place in the universe are, nonetheless, scientific facts. Many nonscientists com-
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