Charles Lyell Publishes The Principles of Geology (1830-33), in Which He Proposes the Actual Age of Earth to be Several Hundred Million Years

views updated

Charles Lyell Publishes The Principles of Geology (1830-33), in Which He Proposes the Actual Age of Earth to be Several Hundred Million Years

Overview

Until relatively recently most people assumed that Earth was relatively young. Charles Lyell, in his work The Principles of Geology, was the first to be taken seriously when proposing an ancient Earth. This, in turn, opened the way for future scientific work, including the entire structure of modern geology, the theory of evolution, and concepts of "deep time" in many branches of science.

Background

Throughout most of human history, people assumed that Earth and all its inhabitants were recently created. In the Western world, the Bible was thought to represent the literal truth about Earth's creation, leading most to conclude that Earth was around 6,000 years old. The concept of an older Earth was not unknown in scientific circles at the beginning of the nineteenth century; Scottish geologist James Hutton had earlier proposed an ancient Earth, but one that was fundamentally different from what we recognize today. Hutton's vision of Earth was of an endless cycle of sediments from the land filling the oceans, turning to rock, and uplifting to form new continents, which then eroded to start the cycle again. Most scientists believed in an old Earth too but felt that most features formed suddenly and catastrophically. The majority of the public, however, believed in a young Earth. These two beliefs—in a young Earth and in Catastrophism—were the generally accepted truths as the nineteenth century opened.

These beliefs led inevitably to others. A young Earth required direct creation of all plants and animals present today, because there was insufficient time for evolution to work. This gave too little time for intelligence to develop, suggesting that humans were created intelligent, having the right to conquer the world. In geology and astronomy, the world and the universe must have achieved their current forms as the result of direct creation or by catastrophic events such as the biblical flood. This view of the universe made humans special beings, created in the image of God and placed squarely at the center of the universe.

Some discoveries, however, started scientists on the path to believing that there might be more to the history of Earth. Galileo, Copernicus, and others removed Earth from the center of the universe, while Hutton's ancient Earth further shook conventional thinking regarding direct creation. Another breakthrough was the understanding that fossils were not only the remains of animals, but that some represented animals that no longer existed. At first these were dismissed as animals that failed to survive the biblical flood, but further discoveries that seemed to show species changing, one into the other, and the discovery of fossils on even the highest mountains slowly began to convince people that poor swimming ability was not the only reason for these creatures' extinction.

In the late 1700s and early 1800s an English canal digger, William "Strata" Smith, noticed a consistent relationship between certain rock layers and the fossils found in them. This led him to suggest that fossils could be used to reliably date rock layers relative to each other, even in areas in which beds of rock may be inclined or overturned.

These scientific discoveries, along with their philosophical and theological implications, occupied the thoughts of religious leaders, theologians, and scientists for some time, setting the stage for the final dethronement of humans as special beings, looked upon with special favor by a divine creator.

Impact

In 1830 Charles Lyell began publication of his three-volume work, Principles of Geology. Drawing upon the Enlightenment tenet that one must follow scientific evidence no matter where it leads, Lyell looked carefully at the evidence and determined that the history of Earth differed radically from the biblical version. This led him to three extremely important conclusions:

1. Earth is much more ancient than can be explained by a literal reading of the Bible.

2. The processes that have formed Earth and the Universe are the same as processes taking place today. This principle—that physical processes are uniform in nature across time—is known as Uniformitarianism.

3. Most of the processes that have shaped Earth and, by extension, the universe, take place over a very long period of time by means of gradual, almost imperceptible, change.

Lyell's conclusions had a strong and immediate impact in scientific and religious circles, an impact that continues in some measure to the present.

From a scientific standpoint Lyell's conclusions were astounding. Science now had vast amounts of time to play with, to fill with events, and to populate with ideas. Under the precepts of Uniformitarianism, scientists could make assumptions about how quickly sediments accumulated or how slowly rock eroded. This, in turn, led to the idea of geologic ages and, coupled with Nicolaus Steno's principle of superposition (the assumption that rocks on top were probably deposited last), allowed geologists to start constructing a geologic history of various regions and, eventually, of Earth itself. Theoretically, scientists could work out the history of Earth from scientific principles rather than by relying on the Bible and other similar documents, thus encouraging natural rather than supernatural explanations for the phenomena that surround us and that shaped Earth.

But Lyell's conclusions reached farther than science. They affected the way that people viewed the Bible and the trust that could be placed in it. Concluding that Earth is ancient (Lyell's estimate was several hundred million years old, as compared to the currently accepted age of 4.6 billion years) directly contradicted the book of Genesis. If accepted, one could no longer believe in the Bible as the literal word of God or as an accurate history of Earth and the universe. Instead, one had to believe that the Bible either contained factual mistakes or that it was allegorical. Either of these alternatives carried profound implications for Western religions.

Finally, Lyell's conclusion that Earth and the universe that surround us are the results of long-term, imperceptible change contradicts both biblical and Catastrophic beliefs. This conclusion led other scientists—notably Charles Darwin and Alfred Wallace—to explore the idea that humans might also be the result of millions of years of imperceptible changes in some other organism. Without the time and the concept of constant, imperceptible change that Lyell's vision gives us, evolution is impossible.

Lyell made some mistakes in constructing his theories. The most serious came from applying his concept of Uniformitarianism too generally. Not only did Lyell state that geological and physical processes were identical at all times, but he also stated that life processes were uniform over time. This led him to the conclusion that, at some time in the future, extinct animals would again walk (or swim or fly) Earth as geologic history repeated itself in a great cycle. Lyell eventually understood this to be erroneous, after Darwin and Wallace published their works on evolution.

It is also worth pointing out that Uniformitarianism has its limits. Recent research indicates that catastrophe does play a part in the history of Earth. Meteor impacts are perhaps the best-known examples, but large volcanic eruptions, the filling of the Mediterranean Sea, the emptying of Lake Missoula to form the Scab Lands of Eastern Washington State, and other sudden events are either global or local catastrophes. An important distinction, however, is that the physical processes leading to these catastrophic events remain constant through time. Or, put another way, the clock may strike suddenly on the hour, but it ticks continually.

Because of his work, Lyell is often referred to as the father of modern geology. He made a methodical effort to lay out an almost heretical theory in meticulous detail, providing over-whelming evidence of its veracity. His conclusions directly influenced Darwin's thinking (Darwin actually read Lyell's books while sailing to South America on the Beagle), setting the stage for the latter scientist's theory of evolution, perhaps the key scientific advance of the nineteenth century. In addition, Lyell's painstaking work encouraged Darwin to write with the same level of detail, which, in turn, gave his Origin of Species added authority. Lyell's scientific style continues to influence the nature of research and scientific writing to this day.

Lyell's work did not have an immediate impact on the average person living in the early nineteenth century. Most people even in his native England had little idea who Lyell was or that anyone was challenging the biblical account of the creation of Earth. However, these matters concerned clergymen, scientists, and the aristocracy, those having the time to think about such matters and the education to appreciate the questions raised. In time, especially after the publication of Darwin's work, an amalgamation of Darwin's theory and Lyell's chronology became better known among the general public.

The subsequent impact of Lyell's work was enormous. Many of the most successful scientific theories of the last 160 years have depended in part on the framework constructed by Lyell. Evolution theory, continental drift, the formation of the universe, and other concepts we take for granted depend on almost imperceptible change over eons. In astronomy, geology, biology, and other sciences, Lyell's concept of uniformity through time is assumed as a given, with some constraints. And these subsequent theories, in turn, have given us the framework of modern scientific knowledge.

P. ANDREW KARAM