Charles Darwin Biography

World of Scientific Discovery on Charles Darwin

One of the most influential scientists of the nineteenth century, Darwin is best known for establishing the theory of organic evolution by natural selection.

Darwin was born in Shrewsbury, England, the son of a respected physician. He was the grandson of the poet-physician Erasmus Darwin (1731-1802) and the porcelain manufacturer Josiah Wedgwood (1730-1795). At age 16, Darwin entered the University of Edinburgh in Scotland with the expectation of becoming a physician. While attending medical classes, however, he was unable to watch actual surgical procedures (often done without anesthesia), and so he was pressured by his family to consider the ministry. Darwin transferred to Christ's College at Cambridge three years later to study theology, but he discovered that he had no religious aspirations, either.

One positive outcome for Darwin during his years at Cambridge was having the opportunity to meet Adam Sedgwick (1785-1873), a professor who interested him in geology. More importantly, he befriended John Stevens Henslow (1796-1861), a botany professor who drew out Darwin's passionate interest in natural history and helped him gain confidence. After graduating from Cambridge in 1831, Henslow invited Darwin to join the crew on a government survey ship, the H.M.S. Beagle, as an unpaid naturalist on a five-year voyage to South America and the South Pacific Islands. Despite his father's reservations, Darwin accepted the offer without hesitation and set sail in December 1831.

While in Brazil, Darwin found his first fossil, the skull of an extinct giant sloth. For the next three years, Darwin made geological and biological observations, took records, and collected specimens of every kind as the ship cruised back and forth along the coasts of South America. Darwin had begun to notice evidence that animals and plants had undergone evolutionary changes. In some areas, species had become extinct, like the gigantic fossil armadillos in South America. Yet Darwin noticed similar but not identical armadillos in other areas nearby. He was perplexed over the fact that existing species had demonstrated characteristics similar to those of extinct species. He also found slightly similar, though clearly different, species located in a variety of places around the world, but also completely lacking in other parts of the world. Moreover, Darwin was intrigued that the flora and fauna of oceanic islands were likely to resemble the same animal and plant species found on the neighboring continents. He thought it peculiar that islands with the same geological and physical features could be home to completely different animal species.

Four years after having set sail, Darwin landed in the Galápagos Islands, where he would make the most significant observations of the expedition. Darwin noticed that there were around 14 different types of finch birds on different islands of the Galápagos. Each type of finch appeared to have adapted completely to the island on which it lived. Moreover, some with sharper, finer beaks fed on insects and were more suited to stabbing their prey, while others ate seeds and had more powerful, parrot-like bills for breaking the shells. Another curiosity were the giant tortoises that appeared similar but possessed many distinctive features. The local island inhabitants could tell at sight from which island any of the giant creatures had come. Darwin began to ask if all of this biological diversity was arbitrary or whether a pattern of meaning could be discerned. Then a possible explanation began to emerge; he realized that species had to be mutable and diverged instead of fixed in form according to their original ancestry. A common ancestor could explain the similarities, but Darwin began to guess that each species could have given rise to new ones.

Upon returning to Britain in October 1836, Darwin's ideas came into focus and he began to synthesize a theory to explain his premonition. He began by asserting that if species had transformed, the issue of diversity was satisfied, but a whole new range of questions emerged. He asked why the bones of a human's arms and legs are similar in general to those of a dog and a horse. He questioned why the embryos of lizards and rabbits are similar, while their adult forms are different. He noticed that many animals, including humans, have functionless organs (e.g., the appendix) and wondered why many different organisms behave in similar ways. Darwin concluded that many of these questions were probably answerable, but only if species were related by descent from common ancestors.

About 50 years earlier, scientists had begun to suggest that there might be a common plan, or a connectivity among animals, that manifested itself in similarities between invertebrates and vertebrates. However, ideas of evolution were cautious and tentative until Darwin published his groundbreaking study The Origin of Species by Means of Natural Selection in 1859. Calling his evolutionary theory the process of natural selection, Darwin asserted that the living organisms that best fit their environment were more likely to survive and pass their characteristics on to their offspring. For example, the white fur of the polar bear blends in with the snowy environment, strongly contrasting with the brown and black fur of bears living in the forest. These different traits among similar animals represent genetic adaptations to different environments.

Darwin's observations were so convincing that he succeeded in persuading most of the scientific community of the real possibility of natural selection and evolution. Toward the end of the 1800s, however, as people increasingly accepted his ideas, they also recognized that Darwin lacked an explanation of how variations were produced or passed on. Without knowing how such variations occurred, natural selection could achieve nothing, asserted Darwin's critics. This rift in Darwin's theory lasted until his ideas merged with those of Gregor Mendel. Mendel proposed in 1866 that the gene was the basic unit of heredity. Although his work was not formally acknowledged until the early 1900s, Mendel demonstrated that genes are the molecular blueprints that are passed on to succeeding generations. With the knowledge of genes as the basic units of heredity, evolutionists (known as neo-Darwinists) were satisfied with the explanation that natural selection involves the evolution of not only physical and behavioral traits, but also the genes that serve as blueprints for those traits.

Darwin initially concentrated on animals and plants, but the ascent or evolution of humankind became the central focus of his book The Descent of Man (1871). Many people were repulsed at the suggestion that human beings could somehow be related to earlier, non-human life forms. In addition, many objections to the book were based on its implicit rejection of man's miraculous creation. Such criticism has lately re-emerged in the United States in the form of creationism, which holds that evolution is nothing more than atheist speculation.

Darwin's important contributions to the biological sciences remain invaluable. Today, despite many modifications to evolutionary theory, it still plays a critical role in modern biology.