FEBRUARY 12th: CHARLES DARWIN DAY
introduction
(1809–1882). The theory of evolution by natural selection that was developed by Charles Darwin revolutionized the study of living things. In his Origin of Species (1859) he provided a scientific explanation of how the diverse species of plants and animals have descended over time from common ancestors. His theory remains central to the foundations of modern biology. Moreover, by demonstrating how natural laws govern the world of living things, Darwin helped usher in a new era in the cultural and intellectual history of humankind.
Charles Robert Darwin was born in Shrewsbury, England, on February 12, 1809. Darwin’s father was a successful and wealthy physician; his mother was a daughter of Josiah Wedgwood, the famous British potter. She died when Charles was eight years old, and the boy was reared by three older sisters, who constantly found fault with him.
Darwin was such an indifferent student that his father said, “You care for nothing but shooting, dogs, and rat-catching, and you will be a disgrace to yourself and all your family.” He had no interest in the classical languages and ancient history taught in school. Instead, he liked to collect shells, birds’ eggs, and coins. He also watched birds and insects and helped his brother make chemical experiments at home.
At the age of 16, Darwin began to study medicine at the University of Edinburgh. There too he found the courses dull, and watching operations made him ill. In 1828 he transferred to Cambridge, intending to become a clergyman. Instead, he devoted most of his time to studying plants and animals and later to geology. He received his bachelor’s degree in 1831.
The Voyage of the Beagle
In 1831, when Darwin was just 22 years old, he set sail on a scientific expedition on a ship called the HMS Beagle. He was the naturalist on the voyage. As a naturalist, it was his job to observe and collect specimens of plants, animals, rocks, and fossils wherever the expedition went ashore. The route the ship took and the stops they made are shown in the figure below.
This map shows the route of Darwin’s 5-year voyage on the HMS Beagle. Each stop along the way is labeled. Darwin and the others on board eventually circled the globe.
Darwin was fascinated by nature, so he loved his job on the Beagle. He spent more than 3 years of the 5-year trip exploring nature on distant continents and islands. While he was away, a former teacher published Darwin’s accounts of his observations. By the time Darwin finally returned to England, he had become famous as a naturalist.
Darwin’s Observations
During the long voyage, Darwin made many observations that helped him form his theory of evolution. For example:
He visited tropical rainforests and other new habitats where he saw many plants and animals he had never seen before (see Figure below). This impressed him with the great diversity of life.
He experienced an earthquake that lifted the ocean floor 2.7 meters (9 feet) above sea level. He also found rocks containing fossil sea shells in mountains high above sea level. These observations suggested that continents and oceans had changed dramatically over time and continue to change in dramatic ways.
He visited rock ledges that had clearly once been beaches that had gradually built up over time. This suggested that slow, steady processes also change Earth’s surface.
He dug up fossils of gigantic extinct mammals, such as the ground sloth (see Figure below). This was hard evidence that organisms looked very different in the past. It suggested that living things—like Earth’s surface—change over time.
On his voyage, Darwin saw giant marine iguanas and blue-footed boobies. He also dug up the fossil skeleton of a giant ground sloth like the one shown here. From left: Giant Marine Iguana, Blue-Footed Boobies, and Fossil Skeleton of a Giant Ground Sloth.
The Galápagos Islands
Darwin’s most important observations were made on the Galápagos Islands (see map in Figure below). This is a group of 16 small volcanic islands 966 kilometers (600 miles) off the west coast of Ecuador, South America.
This map shows the location of the Galápagos Islands that Darwin visited on his voyage.
Individual Galápagos islands differ from one another in important ways. Some are rocky and dry. Others have better soil and more rainfall. Darwin noticed that the plants and animals on the different islands also differed. For example, the giant tortoises on one island had saddle-shaped shells, while those on another island had dome-shaped shells (see Figure below). People who lived on the islands could even tell the island a turtle came from by its shell. This started Darwin thinking about the origin of species. He wondered how each island came to have its own type of tortoise.
video: darwin in the galapagos
Summary
Darwin’s theory of evolution by natural selection states that living things with beneficial traits produce more offspring than others do. This produces changes in the traits of living things over time.
During his voyage on the Beagle, Darwin made many observations that helped him develop his theory of evolution.
Darwin's most important observations were made on the Galápagos Islands.
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