Explorers and scientists had found fossils in deep layers of rock widely separated by other layers of rock, leading many of them to conclude that now-extinct forms of life had existed before the Biblical flood. A pioneer French paleontologist, Georges Cuvier, tried to solve this dilemma in the late 1700s by postulating that there must have been several worldwide floods before the one described in the Christian Bible. Finally, this solution collapsed under the weight of new evidence as more and more studies proceeded.
In the 1830s an English geologist, Sir Charles Lyell, popularized the principle of uniformitarianism—the idea that processes we observe now, such as the steady erosion of mountains, the gradual buildup of silt as sediments in rivers, lakes, and oceans, have always occurred since the origin of the Earth. This, he then reasoned, meant that the Earth must be many millions of years old at least, instead of merely a few thousand years old.
A wave of interest in fossils and their antiquity swept communities around the world in the 1840s and 1850s. Americans interested in science from Thomas Jefferson on had advocated the collection and study of fossils, and a feverish race to build up study collections got underway that lasted into the 20th century. Today, scientists believe the Earth is more than 4.5 billion years old, its life more than 3 billion years old.
[Illustration: Karl Von Linné, 1707-1778, is known as Linnaeus after the Latin form of his name. A Swedish botanist, he established a hierarchical system for classifying plants and animals that is still in use in a modified form. His organizing principle was the degree of complexity of the organisms he studied. This resulted in a system with seven levels: Kingdom, Phylum, Class, Order, Family, Genus, and Species, in descending order from the broadest category to the most specific. Students remember the system by the sentence “King Philip Crossed the Ocean For Good Soup.” Without realizing it, Linnaeus prepared the ground for the evolutionists, who later were able to demonstrate the gradual ascent of life forms from simple to complex by using his scheme of classification.]
[Illustration: Jean-Baptiste de Lamarck, 1744-1829, a French physician and ex-military man, founded the modern study of animals without backbones and coined the term invertebrates to describe them as a group. When his battle wounds forced him to take up a new career, he studied botany and published a study of French plants. He later turned to invertebrates, and between 1815 and 1822 published the classic _Histoire naturelle des animaux sans vertèbres_. He applied his vast knowledge of living invertebrates to paleontological work, greatly enhancing the knowledge of fossil invertebrates. Lamarck was also an evolutionary theorist, and he believed that a single characteristic acquired by an animal during its lifetime could be passed on to its descendants by heredity (modern genetic theory was unknown at that time). He saw that evolution must have taken a long time to occur, and he supported the principle which has since become known as uniformitarianism.]