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Welcome to the Geological Society of London, one of the organisations participating in the ‘Charles Darwin: A Genius in the Heart of London’ project. Darwin is famous throughout the world for his theory of evolution through natural selection, and so is principally remembered as biologist. One of his earliest interests, however, was geology; a science which drove much of his thinking throughout his career. Background As Darwin grew up, the predominant theory in geology was catastrophism – the idea that the Earth changes by sudden, short-lived, violent events like floods and earthquakes. This was closely related to the church’s view of creation – animals and plants were created, and only disappeared when they were wiped out in a catastrophe, and replaced with new species. Darwin’s family, by contrast, was strongly in favour of an alternative paradigm called uniformitarianism. Uniformitarians held that the processes that shaped the Earth are still happening now, and by observing the Earth now, we can infer what happened to it in the past. Although the idea had been around for centuries, in Darwin’s time it was made popular by Charles Lyell, whose book, ‘Principles of Geology‟ popularised the famous term ‘the present is the key to the past‟. At Cambridge Darwin’s interest in geology began even before his journey on The Beagle. At Cambridge, he met the geologist Adam Sedgwick (1785 – 1873). In August 1831 he accompanied Sedgwick on a geological mapping tour of Wales. Statue of Darwin as a student at his college, Christ‟s. The Voyage of the Beagle Between 1831 and 1836, Darwin travelled as a naturalist on HMS Beagle; a journey that was to change his life. As a welcoming gift, the ship’s Captain, Robert FitzRoy, presented him with a copy of Charles Lyell’s recently published Principles of Geology. Lyell’s ideas were a huge influence on Darwin. From the ship, Darwin wrote home to his sisters that he “literally could not sleep for thinking over my [geology]” During the five year voyage, Darwin wrote 1,383 pages of notes about geology – compared to a mere 368 pages of notes on plants and animals. Chilean earthquake On February 20 1835, Darwin was in the town of Valdivia, Chile. At 11.30 in the morning, a massive earthquake struck: “I happened to be on shore, and was lying down in the wood to rest myself. It came on suddenly, and lasted two minutes, but the time appeared much longer. The rocking of the ground was very sensible”. They spent the next few days surveying the damage. On 4 March, Darwin was dropped off at the island of Quiriquina, where he found that parts of the coastline had been raised up as a result of the earthquake. He also noticed raised shell beds on the cliffs above – evidence that the Andes mountains were slowly rising above the ocean. These discoveries supported Lyell’s theory that land masses rise in tiny increments over geological time. Coral reefs Darwin’s observations of the aftermath of the Chilean earthquake allowed him to hypothesise, before having seen them, how the coral reefs of the Pacific were formed. “No other work of mine was begun in so deductive a spirit as this; for the whole theory was thought out on the west coast of S. America before I had seen a true coral reef”. Because he had seen evidence for the elevation of land, Darwin hypothesised that land must also subside. His theory was that if coral reefs develop on the margins of subsiding land masses, they will grow upwards as the land subsides so that the organisms have enough sunlight. Eventually, as the land sinks beneath the surface, only the coral is visible. Coral reefs were a subject of some controversy at the time, and one of the Beagle‟s objectives was to find out more about how they formed. In Principles of Geology, Lyell suggests that atolls (circular reefs) grew up from the craters of sunken volcanoes. When Darwin shared his alternative theory with him, Lyell is said to have been so excited that he danced around the room, shouting and laughing. Darwin eventually published his theories on coral reefs in The structure and distribution of coral reefs (1842) – a copy of which is on display in the cabinet. He was eventually proved right with deep borings were carried out on Bikini Atoll in the 1950s. Fossil samples Darwin collected many things on his travels, including numerous fossil samples. Fossils were crucial to his ideas about evolution. In Punta Alta, a city in Argentina, he discovered a fossil that was unlike anything living he had seen before. This led him to consider extinction, and the impact of environmental change. Whilst walking along the shoreline during his stay in the Falkland Islands, he noted how different the fossils here were to those he had found on the coast of South America. He carried out comparative studies of the samples he had collected from various locations. This was the beginning of his thinking about different species adapting to different environments. Darwin sent many of the samples he collected back to England, where they were beginning to make his name famous in scientific circles. Many were described and illustrated by the naturalist and illustrator, G. B. Sowerby. Some of Sowerby’s drawings are displayed in the cabinet, along with a selection of fossils that Darwin would have come across on his journey. „Most of the arguments which have convinced me that all the existing species of the same group are descended from a single progenitor, apply with equal force to the earliest known species. For instance, it cannot be doubted that all the Cambrian and Silurian trilobites are descended from one crustacean, which must have lived long before the Cambrian age, and which probably differed greatly from any known animal.‟ - C. Darwin, ‘On the Origin of Species’ Evolution It is for his theory of evolution by natural selection that Darwin is now chiefly remembered. Without his insight into geology, as well as many other branches of science, his theory might not have been developed. If it had, it would certainly have been less convincing - it was the breadth of Darwin’s research and his ability to draw on such variety of evidence that made his theory so compelling. From the diversity of fossils he saw, he was able to consider how species evolve differently in different environments. The earthquake he witnessed made him think about whether the Earth is as solid as it appears, and how it might be constantly changing under our feet. Coral reefs allowed him to think about how movements of the Earth affect the lives of creatures that live on it. Most importantly, the study of geology taught Darwin that, although the Earth seems static, it is constantly changing so slowly that we hardly notice it. In the same way, living creatures are constantly changing in tiny ways which, over geological time scales, give rise to entirely new species. About the project ‘Charles Darwin: A Genius in the Heart of London’ is a Heritage Lottery funded project that brings together the various organisations in Westminster with which Darwin was associated. Led by the Linnean Society of London and the Westminster Archives, the project brings together the Geological Society, the Zoological Society, the Royal Society, the Royal Geographical Society and Westmister Abbey. The project focuses on the many facets of Darwin’s life and scientific work which linked him to London. In Darwin’s lifetime, London, and more specifically Westminster, was the main hub of the scientific world. Over the course of the project a wide range of activities have been held for all ages, particularly for young people in Westminster schools. Activities have ranged from animation to art, tapestry to songwriting, debate to drama; all with Darwin as the focus. For more information, visit the project website, www.darwininlondon.co.uk.