The Sixth Extinction: An Unnatural History

Concepción’s harbor showed that the quake had elevated the beach by
nearly eight feet. Once again, Lyell’s Principles appeared to be rather
spectacularly confirmed. Given enough time, Lyell argued, repeated
quakes could raise an entire mountain chain many thousands of feet high.
The more Darwin explored the world, the more Lyellian it seemed to
him to be. Outside the port of Valparaiso, he found deposits of marine
shells far above sea level. These he took to be the result of many episodes
of elevation like the one he’d just witnessed. “I have always thought that
the great merit of the Principles was that it altered the whole tone of one’s
mind,” he would later write. (While in Chile, Darwin also discovered a new
and rather remarkable species of frog, which became known as the Chile
Darwin’s frog. Males of the species incubated their tadpoles in their vocal
sacs. Recent searches have failed to turn up any Chile Darwin’s frogs, and
the species is now believed to be extinct.)
Toward the end of the Beagle’s voyage, Darwin encountered coral
reefs. These provided him with his first major breakthrough, a startling
idea that would ease his entrée into London’s scientific circles. Darwin
saw that the key to understanding coral reefs was the interplay between
biology and geology. If a reef formed around an island or along a
continental margin that was slowly sinking, the corals, by growing slowly
upward, could maintain their position relative to the water. Gradually, as
the land subsided, the corals would form a barrier reef. If, eventually, the
land sank away entirely, the reef would form an atoll.
Darwin’s account went beyond and to a certain extent contradicted
Lyell’s; the older man had hypothesized that reefs grew from the rims of
submerged volcanoes. But Darwin’s ideas were so fundamentally Lyellian
in nature that when, upon his return to England, Darwin presented them
to Lyell, the latter was delighted. As the historian of science Martin
Rudwick has put it, Lyell “recognized that Darwin had out-Lyelled him.”
One biographer summed up Lyell’s influence on Darwin as follows:
“Without Lyell there would have been no Darwin.” Darwin himself, after
publishing his account of the voyage of the Beagle and also a volume on