Charles Darwin, Geologist (review)

Today, Charles Darwin is world famous (and, for some, infamous), but not for his accomplishments as a geologist. Yet Darwin pursued a career in geology, and in so doing he achieved such distinction that in February 1859, when he was fifty years old, the Geological Society of London presented him with its highest honor, the Wollaston Medal, for his outstanding contributions to geology. Charles Lyell, the citationist, listed Darwin's studies on the growth of coral reefs, his evidence for the modern elevation of Chile and repeated elevations of the Andes, and his observations about South American geology and the distribution of boulders in Britain.

It was not until eight months later that Darwin introduced an evolutionary perspective into geology and biology with his On the Origin of Species by Means of Natural Selection (1859). He was not the first scientist to favor such a hypothesis, but he was the first to propose a causal mechanism for it: natural selection. His book forced life scientists and geologists (especially paleontologists and stratigraphers) to choose whether or not to incorporate this new hypothesis into their interpretations of the Earth's history. A similar choice began to pervade public discourse, thereby gaining for Darwin many supporters and countless opponents who are continuing to strive with one another to this day.

Sandra Herbert's biography of Darwin traces his career as a geologist and examines how it led to the Origin. Herbert, a preeminent Darwin scholar with a fine writing style and great skill at clearly explaining difficult materials, has edited some of Darwin's notebooks and is intimately familiar with the full range of his published and unpublished writings. As she introduces each new topic in Darwin's career, Herbert turns to the notebooks to reveal Darwin's impressions. The resulting insights make enormously interesting passages in each of her chapters.

Herbert notes that Darwin's education as a geologist in the early nineteenth century took place when geology itself was developing as a science. At Cambridge in 1831, Darwin had invaluable mentoring by two eminent geologists, John Stevens Henslow, who "crammed" him in geology, and Adam Sedgwick, who trained him in field work. Henslow also gave him the priceless chance to spend five years, 1831 to 1836, sailing around the world on H. M. S. Beagle by turning down that opportunity himself. As the ship's naturalist, Darwin enjoyed an unusual degree of freedom to work on projects of his own choosing. He bunked in the small cabin on the poop deck that housed the ship's library of more than 245 volumes. In addition, he purchased and carried aboard a sizable collection of geological books. And the ship's captain, Robert FitzRoy, brought along many books on voyages. Darwin's reading at sea constituted what he called his self-education.

The single most memorable book he read (inscribed: "From Capt FitzRoy") was the newly published volume I of Lyell's Principles of Geology, Being an Attempt to Explain the Former Changes of the Earth's Surface, by Reference to Causes Now in Operation (1830). It was a revelation to Darwin. He sent for volume II and picked it up in November 1832 at Montevideo, and then for volume III, which he seems to have picked up in March 1834 at the British station in the Falkland Islands. Lyell dispensed entirely with the Biblical flood and timescale and portrayed the Earth as an essentially steady state system with a cyclic history during which periods of regional elevation, balanced by subsidence, had repeatedly reconfigured the distribution of lands and seas and, hence, of climatic zones. He declared that to explain past events in geology we may call upon only those processes we witness in operation today, proceeding at their present rates.

By the time he arrived home in England, in October of 1836, Darwin was a Lyellian uniformitarian in search of a "simple geology" based on vertical movements that would account for the Earth's history without recourse to unfamiliar forces. According...