Charles Darwin introduced a new way of seeing the world that was both highly criticized and acclaimed in the scientific community of his time. In spite of resistance by various segments of society, his theories of natural selection became the foundation of biological science. New knowledge pertaining to genetics and molecular science has strengthened Darwin’s theories rather than weakened them. Darwin the Apprentice When he was 17 years old, well before he gained a reputation as a naturalist, scholar, and scientist, Darwin was studying to be a medical doctor at the University of Edinburgh. Like many young people, he began to question his original choice of studies, and he decided to instead learn taxidermy under John Edmonstone. John Edmonstone was born enslaved and grew up on a plantation owned by a Scottish politician in what is now Guyana in South America. Charles Waterton, the son-in-law of the plantation owner and a renowned naturalist, would visit the plantation often. He started inviting Edmonstone to accompany him on his frequent travels into the rainforest. On his travels, Edmonstone gained considerable knowledge about the flora and fauna of South America along with impressive taxidermy skills. After gaining his freedom in 1817, John Edmonstone taught taxidermy at the University of Edinburgh, where he served as a mentor to Darwin over a period of several months. It is believed that Darwin’s relationship with Edmonstone may have influenced his abolitionist views, which were later strengthened by firsthand accounts of slavery while Darwin was on his infamous voyage to the Galápagos Islands off the coast of Ecuador. Figure 4.10 At the University of Edenborough, John Edmonstone taught Darwin how to preserve birds. This is an example of Embernagra platensis, the great Pampa-finch, collected by Charles Darwin in Uruguay in May of 1833. (credit: “Embernagra platensis platensis, Great Pampa-finch, skin. Syntype. [B 19600]” by Michelle McFarlane/Museums Victoria, CC BY 4.0) Darwin the Explorer and Scholar Charles Darwin left the University of Edinburgh and decided to pursue theology at Christ’s College, Cambridge. His studies there led to his appointment in 1831 as a naturalist on the HMS Beagle for a five-year scientific expedition around the world. During this voyage, Darwin collected, dissected, and organized various specimens, especially in the Galápagos Islands, a chain of islands off the western coast of South America. His observations in the Galápagos marked a crucial point in his thinking on evolution. He noted that the fauna and flora of the western coast of South America were similar to those he observed in the Galápagos, but still distinct enough to be considered different species. More surprisingly, the animals of each of the various islands in the Galápagos chain differed slightly from one another. Darwin observed 13 different types of finches throughout 13 different small islands. The birds on each island differed in the structure of their beaks, their body form, and the color of their feathers. Each species was specifically adapted to the specific habitats on each of the islands. Darwin used the techniques that Edmonstone taught him to preserve the Galápagos finches, which became key pieces of evidence supporting Darwin’s theory of natural selection. Figure 4.11 Charles Darwin is acknowledged as the father of the theory of natural selection. His work built upon the ideas of many other thinkers. His great contribution was in synthesizing these ideas into a coherent theory explaining the diversity of life on earth and the great changes in life over geological time. (credit: A. C. Seward, Cambridge Philosophical Society, Cambridge University Press/Wikimedia Commons, Public Domain) During his travels on the Beagle, Darwin had been thinking about artificial selection—the selective breeding of animals to produce traits that humans find useful, commonly associated with the process of domestication. Darwin understood that artificial selection provided important clues about the natural evolution of species. While on board the HMS Beagle, Darwin read a book by English economist Thomas Robert Malthus titled An Essay on the Principle of Population (1798). Darwin obtained two important points from this book. The first was that human populations, if unrestrained, will grow exponentially. This means that they will double each generation. The second point was that food resources increase much more slowly than population does. Malthus noted that the growth of human populations is kept in check by a limit of food resources, which creates a struggle for existence. The struggle for existence is not just about getting enough food but also about survival. In other words, it is about an individual’s ability to both find enough food and not become another organism’s food. This simple concept, the struggle for existence, provided Darwin with a mechanism for how evolution could occur. Darwin realized that individuals with favorable characteristics for living in an environment are the ones that will survive to the age at which they reproduce, while those with less favorable variations will not. This mechanism for “selecting for” certain traits and features is known as the theory of natural selection. Darwin concluded from his observations that when a group of animals of the same species are geologically separated, they develop into separate species. This evolutionary process is commonly referred to as allopatric speciation (or geographic speciation) and is based on the principles that related species share a common ancestor and that species change over time. Darwin did not originate the idea of evolution. Many of the ideas used by Darwin in his theory of natural selection were developed by other thinkers. Darwin was also not the only person thinking about natural selection. Another British natural historian, Alfred Russel Wallace, developed the same idea at roughly the same time, entirely independently of Darwin. Whereas Darwin developed his ideas based on his travels to the Galápagos, Wallace’s thinking was influenced by his own travels through the Malay Archipelago between Indochina and Australia. Wallace outlined his theory of evolution by natural selection in a letter written to Darwin while he was in Malaysia. As Darwin had not yet published his own work, Wallace and Darwin jointly presented papers introducing the theory of natural selection. In 1859, Darwin finally published his book On the Origin of Species, some 20 years after his voyage on the HMS Beagle.