Page 25 - Introduction to Paleobiology and The Fossil Record

12 INTRODUCTION TO PALEOBIOLOGY AND THE FOSSIL RECORD

The idea of extinction
Robert Hooke was one of the fi rst to hint at
the idea of extinction, a subject that was hotly
debated during the 18th century. The debate

fizzed quietly until the 1750s and 1760s when
accounts of fossil mastodon remains from
North America began to appear. Explorers
sent large teeth and bones back to Paris and
London for study by the anatomic experts of
the day (normal practice at the time, because
the serious pursuit of science as a profession
had not yet begun in North America). William (a)
Hunter noted in 1768 that the “American
incognitum” was quite different from modern
elephants and from mammoths, and was
clearly an extinct animal, and a meat-eating
one at that. “And if this animal was indeed
carnivorous, which I believe cannot be
doubted, though we may as philosophers
regret it,” he wrote, “as men we cannot but
thank Heaven that its whole generation is
probably extinct.”
The reality of extinction was demonstrated
by the great French natural scientist Georges
Cuvier (1769–1832). He showed that the (b)
mammoth from Siberia and the mastodon
from North America were unique species, and Figure 1.8 Proof of extinction: Cuvier’s
different from the modern African and Indian comparison of (a) the lower jaw of a mammoth
elephants (Fig. 1.8). Cuvier extended his and (b) a modern Indian elephant. (Courtesy of
studies to the rich Eocene mammal deposits Eric Buffetaut.)
of the Paris Basin, describing skeletons of
horse-like animals (see Fig. 1.4), an opossum, documented the history of long spans of time.
carnivores, birds and reptiles, all of which Until the late 18th century, scientists accepted
differed markedly from living forms. He also calculations from the Bible that the Earth was
wrote accounts of Mesozoic crocodilians, only 6000–8000 years old. This view was
pterosaurs and the giant mosasaur of challenged, and most thinkers accepted an
Maastricht. unknown, but vast, age for the Earth by the
Cuvier is sometimes called the father of
comparative anatomy; he realized that all 1830s (see p. 23).
The geological periods and eras were named
organisms share common structures. For through the 1820s and 1830s, and geologists
example, he showed that elephants, whether realized they could use fossils to recognize all
living or fossil, all share certain anatomic major sedimentary rock units, and that these
features. His public demonstrations became rock units ran in a predictable sequence every-
famous: he claimed to be able to identify and where in the world. These were the key steps
reconstruct an animal from just one tooth or in the foundations of stratigraphy, an under-
bone, and he was usually successful. After standing of geologic time (see p. 24).
1800, Cuvier had established the reality of
extinction.
FOSSILS AND EVOLUTION
The vastness of geological time Progressionism and evolution

Many paleontologists realized that the sedi- Knowledge of the fossil record in the 1820s
mentary rocks and their contained fossils and 1830s was patchy, and paleontologists